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Session 2
Fundamentals of Accuracy Assessment

        Raymond L Czaplewski

       United States Forest Service
     Rocky Mountain Research Station
        Fort Collins, Colorado USA
                                       1
Session 2 Topics
• Different sample designs
    – Simple Random Sampling (Systematic Sampling)
    – Stratified Random Sampling
•   Different sample survey estimators
•   Different sample sizes, n=30, 60, 150
•   How close are estimates to true value?
•   Example of a 30×30 = 900 pixel world

                                                     2
Hypothetical “real world”

                                  True (reference) population
N   N   N   N   N   ^   N   ^     ^     ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N
N   N   N   N   N   ^   ^   ^ N     ^ ^ ^   ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^
N   N   N   N   N   ^   ^   ^ ^     ^ ^ ^ ^   ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   N   ^
N   N   N   ^   N   ^   ^     ^   ^   ^ N ^ ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   ^   N
N   N   N   N   ^   ^   ^   ^ ^       ^     ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   ^
N   N   N   N   N   ^       ^               ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   N   N
N   N   N   ^   ^   ^       ^       N       ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N
N   N   N   N   N   ^   ^   ^                 ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   N   N
N   N   N   ^   N   ^       ^               ^       ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   ^   ^
N   N   N   N   ^   N   ^   ^               ^ ^         ^   ^   ^   ^   ^   ^   ^   ^       ^   N   N
N   N   N   ^   ^   N   ^   ^               ^           ^   ^   ^   ^   ^   ^   ^   ^           ^   ^
N   N   N   ^   N   ^       ^               N ^         ^   ^   ^   ^   ^   ^   ^   ^           ^   N
N   N   N   ^   N   N       ^ ^             ^ ^     ^   ^   ^   ^   ^   ^       ^                   N
N   N   N   N   N   ^   ^   ^ ^   ^     ^   ^ ^ ^   ^   ^   ^   ^   ^   ^
N   N   N   N   ^   ^   ^   ^ ^       ^ ^ ^ ^ ^ ^   ^   ^   ^   ^   ^   ^                       N ^
N   N   N   N   ^   N   ^     ^       ^ ^ ^ ^ ^ ^   ^   ^   ^   ^   ^                                   Reference class
N   N   N   N   ^   N   ^     ^   ^ ^ ^ ^     ^ ^   ^   ^   ^   ^   ^   30×30 = 900 pixels      ^ ^




                                                                                                         Natural
N   N   N   N   N   N   N   ^         ^     ^ ^ ^   ^   ^   ^   ^   ^                             ^




                                                                                                         Urban
                                                                                                                   Crop
N   N   N   N   ^   ^   ^     ^   N N N N     ^ ^   ^   ^   ^   ^   ^       N                   ^ ^
N   N   N   N   ^   N   ^   ^ N   N N N N N ^ ^ ^   ^   N   ^   ^   ^                           ^ ^
N   N   N   N   N   N   ^   ^ ^   N N N N N N ^ ^   ^   N   ^   ^   ^                           ^ N
N   N   N   N   ^   N   N   ^ N   N N N N N N N ^   ^   N   N   ^   ^                           N ^
                                                                                                          N         ^
N   N   N   N   N   ^   ^   N N   N N N N N N N ^   N   N   N   N   ^   ^                       N N
N   N   N   N   ^   ^   N   ^ ^   N N N N N N N ^   N   N   N   N   N   ^       ^           N   ^ ^
N   N   N   N   ^   N   ^   ^ N   N N N N N N N N   N   N   N   N   N   ^       ^   ^       N   ^ ^
N   N   N   N   N   N   ^   ^ N   N N N N N N N N   N   N   N   N   N   ^   ^   ^   ^   ^   N   ^ ^
N   N   N   N   ^   N   ^   ^ ^   N N N N N N N N   N   N   N   N   N   ^   ^   ^   N   N   N   ^ N
N   N   N   N   N   N   ^   N ^   N N N N N N N N   N   N   N   N   N   ^   ^   ^   N   ^   N   ^ ^
N   N   N   N   N   N   N   ^ N   N N N N N N N N   N   N   N   N   N   ^   ^   ^   ^   N   ^   N N
N   N   N   N   N   N   ^   ^ ^   N N N N N N N N   N   N   N   N   N   ^   ^   ^   N   ^   ^   ^ ^                       3
Hypothetical remotely sensed thematic map model for this “real world”

                                              Map #1
N   N   N   ^ N ^ N   ^   ^           ^   ^
                                          N        ^   ^   ^   N     ^ ^ ^ ^ ^   ^   ^ ^   N
N   ^   N   N   ^ N   ^ N     ^   ^   N   ^
                                          ^    N   N   ^   ^   ^   ^ ^ ^ ^ ^ ^   ^     ^   ^
N   N   ^   N N   N   ^ ^ N   ^   ^   ^   ^
                                          ^    ^   ^   ^   ^   ^   ^ ^ ^ ^ N ^   N   ^ N   ^
^   N   ^     N ^ N     ^ ^   ^   ^   N   ^
                                          ^    ^   N   ^   ^   N   ^ N   N ^     N   ^ ^   N
N   N   ^   N ^ ^ ^   ^ N     N   ^   N   ^        ^           ^   ^ ^ ^ ^ N N   N   ^ N   ^
N   N   N   ^ N ^     ^           ^     N ^   ^    ^   ^   ^   ^   ^ N ^ ^   ^   N   N N   ^
N   N   N   ^ ^ ^ ^           N       ^   ^   N    N   ^   N   ^   ^ ^ N ^ ^ ^   ^   ^ N   N
    N   N     N ^     ^       N N             ^    ^   ^   N   ^   ^ ^ ^ N N N   ^   ^ ^
N   N   ^   ^ N ^     N         N           ^ ^        ^   ^   ^     ^   N ^ ^   N   ^ N
                                                                                       N
N   N   ^   N   ^ ^   ^       ^   N       ^ ^ N ^          ^   ^   ^ ^ ^ ^ ^     ^   ^ N
                                                                                       N
N   N   ^   ^ ^   N               N       N ^   ^          N   ^   ^ ^ ^ ^ ^ ^   ^   ^ N
                                                                                       N
N   N   ^   ^ ^       ^   N     N N         ^ N            ^   ^   ^ ^ N ^ ^ N         ^
                                                                                       ^
N   ^   ^     N ^     ^ ^     N               ^        ^   ^   ^   ^ ^ ^               N
^   N   N   N N ^ ^   ^ ^ ^   ^   N         ^ ^ ^      ^   ^   ^   ^ ^ ^   ^ N         ^
N   N   ^   N ^ ^ ^   ^         ^ ^       ^ ^ ^ N      ^   ^   N   ^ ^ ^ N         ^ N ^
N   ^   N   N   ^ ^     ^       N ^       ^ ^ ^ ^      N   ^   ^   ^ ^   N N           ^
N       N   N ^ N ^     ^ ^   N ^ ^         ^ ^        ^   ^   ^   ^ ^ ^ 30×30 = 900 pixels
                                                                           N     ^ ^   ^
^   ^       N N ^ N   ^   ^     ^             ^ N      ^   ^   ^   ^ ^     ^ N   ^ N   ^
N   N N     N ^ ^ ^   ^ ^ N   N N N         N ^ ^      ^   ^   ^   N ^   N ^ N   ^   ^
N   N N     N ^ ^ ^   ^ N N   N ^ N       N ^ ^ ^      N   N   N   ^   ^ ^ ^     ^   N ^




                                                                                               Map class
N   N N     N N N ^   ^   N   ^ N ^       N N ^ N      ^   N   ^   N ^   N ^     N   ^ N
N     ^     N ^ N N     N N   N N N       ^ ^ N N      ^   N   ^   ^ ^     N       N N ^
                                                                                                           Natural N
N   N N     ^ ^ ^ ^   N N N   N N N         N ^ N      ^       ^   N ^               ^ ^                   Urban
^   N ^     ^ N ^ ^   ^ ^ N   N N ^       ^ N N ^      N N     N   N N ^   ^ ^     N ^ ^
N   ^ N     ^ ^ N ^   N N N   N N         ^ N ^ ^      N N     N   N N ^ ^ ^ ^   ^ N ^ ^
                                                                                                           Crop    ^
^   ^ N     N N N ^   N ^ N   N N ^       N N N N      N N     N   N N N ^ ^ ^   ^ N ^ N
N   ^ N     ^   N N   ^ N N   N   N       N ^          N N     ^   N ^ ^ N N ^   ^ N N N
^   N ^     N N N N     N N   N N N       ^ N N ^        ^     N   ^ N     N ^   ^   ^
^   N N     N N N ^   ^ N N   N N N       ^   N N      N N     N   N N ^ N N     ^ N N ^
N   N N     N ^ N ^     N ^   N N N       N ^ N N      N N     ^   ^ ^ ^ ^ ^ N   N ^ N ^                               4
Remotely sensed thematic Map #1                                                                                                                  True Error Matrix
   Error matrix presented by Steve Stehman                                                                                                Reference class
                                                                                                                                     Natural    Urban      Crop Total
             Traditional Analysis: Error                                                                                   Natural       226       27        74 327




                                                                                                               Map class
                (Confusion) Matrix                                                                                          Urban         18      108        36 162
                  Reference Land Cover
                                                                                                                             Crop         89       36       286 411
     Mapped Natural Urban      Crop                                                        Total
                                                                                                                             Total       333      171       396 900
     Natural 0.25     0.03     0.08                                                        0.36                             Overall accuracy 69%          kappa 51%
     Urban   0.02     0.12     0.04                                                        0.18                                                           Reference class
     Crop    0.10     0.04     0.32                                                        0.46                                                      Natural    Urban                            Crop Total
                                                                                                                           Natural                      25%        3%                              8% 36%




                                                                                                               Map class
     Total   0.37     0.19     0.44
                                                                                                                            Urban                        2%       12%                              4% 18%
                                                                                                                             Crop                       10%        4%                             32% 46%
                                                                                                                             Total                      37%       19%                             44% 100%
                 True (reference) population                                                                                                                         Map #1
         N   N   N   N   N   ^   N   ^     ^     ^ ^ ^   ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N               N   N   N   ^ N ^ N   ^   ^           ^   ^
                                                                                                                                                                     N       ^ ^ ^   N       ^
                                                                                                                                                                                             ^ ^ ^ ^   ^   ^ ^   N
         N   N   N   N   N   ^   ^   ^ N     ^ ^ ^   ^ ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^               N   ^   N   N   ^ N   ^ N     ^   ^   N   ^
                                                                                                                                                                     ^     N N ^ ^   ^   ^   ^
                                                                                                                                                                                             ^ ^ ^ ^   ^     ^   ^
         N   N   N   N   N   ^   ^   ^ ^     ^ ^ ^ ^   ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   N   ^               N   N   ^   N N   N   ^ ^ N   ^   ^   ^   ^
                                                                                                                                                                     ^     ^ ^ ^ ^   ^   ^   ^
                                                                                                                                                                                             ^ ^ N ^   N   ^ N   ^


                                                                                                       30×30 = 900 pixels
         N   N   N   ^   N   ^   ^     ^   ^   ^ N ^ ^ ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   ^   N               ^   N   ^     N ^ N     ^ ^   ^   ^   N   ^
                                                                                                                                                                     ^     ^ N ^ ^   N   ^   N N ^     N   ^ ^   N
         N   N   N   N   ^   ^   ^   ^ ^       ^     ^   ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   ^               N   N   ^   N ^ ^ ^   ^ N     N   ^   N   ^       ^       ^   ^   ^
                                                                                                                                                                                             ^ ^ N N   N   ^ N   ^
         N   N   N   N   N   ^       ^               ^ ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   N   ^   N   N               N   N   N   ^ N ^     ^           ^     N ^     ^ ^ ^ ^   ^   ^   N
                                                                                                                                                                                             ^ ^   ^   N   N N   ^
         N   N   N   ^   ^   ^       ^       N       ^ ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N               N   N   N   ^ ^ ^ ^           N       ^   ^     N N ^ N   ^   ^   ^
                                                                                                                                                                                             N ^ ^ ^   ^   ^ N   N
         N   N   N   N   N   ^   ^   ^                 ^ ^ ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   N   N                   N   N     N ^     ^       N N               ^ ^ ^ N   ^   ^   ^
                                                                                                                                                                                             ^ N N N   ^   ^ ^
         N   N   N   ^   N   ^       ^               ^     ^   ^   ^   ^   ^   ^   ^   ^   ^   N   N   ^   ^               N   N   ^   ^ N ^     N         N           ^   ^   ^ ^   ^       ^ N ^ ^   N   ^ N
                                                                                                                                                                                                             N
         N   N   N   N   ^   N   ^   ^               ^ ^       ^   ^   ^   ^   ^   ^   ^   ^       ^   N   N               N   N   ^   N   ^ ^   ^       ^   N       ^ ^   N ^   ^   ^   ^   ^
                                                                                                                                                                                             ^ ^ ^     ^   ^ N
                                                                                                                                                                                                             N
         N   N   N   ^   ^   N   ^   ^               ^         ^   ^   ^   ^   ^   ^   ^   ^           ^   ^               N   N   ^   ^ ^   N               N       N ^     ^   N   ^   ^   ^
                                                                                                                                                                                             ^ ^ ^ ^   ^   ^ N
                                                                                                                                                                                                             N
         N   N   N   ^   N   ^       ^               N ^       ^   ^   ^   ^   ^   ^   ^   ^           ^   N               N   N   ^   ^ ^       ^   N     N N         ^   N     ^   ^   ^   ^
                                                                                                                                                                                             N ^ ^ N         ^
                                                                                                                                                                                                             ^
         N   N   N   ^   N   N       ^ ^             ^ ^   ^   ^   ^   ^   ^   ^       ^                   N               N   ^   ^     N ^     ^ ^     N                 ^   ^ ^   ^   ^   ^
                                                                                                                                                                                             ^               N
         N   N   N   N   N   ^   ^   ^ ^   ^     ^   ^ ^ ^ ^   ^   ^   ^   ^   ^                                           ^   N   N   N N ^ ^   ^ ^ ^   ^   N         ^   ^ ^ ^ ^   ^   ^   ^
                                                                                                                                                                                             ^   ^ N         ^
         N   N   N   N   ^   ^   ^   ^ ^       ^ ^ ^ ^ ^ ^ ^   ^   ^   ^   ^   ^                       N ^                 N   N   ^   N ^ ^ ^   ^         ^ ^       ^ ^   ^ N ^ ^   N   ^   ^
                                                                                                                                                                                             ^ N         ^ N ^
         N   N   N   N   ^   N   ^     ^       ^ ^ ^ ^ ^ ^ ^   ^   ^   ^   ^                                               N   ^   N   N   ^ ^     ^       N ^       ^ ^   ^ ^ N ^   ^   ^   ^ N N           ^
         N   N   N   N   ^   N   ^     ^   ^ ^ ^ ^     ^ ^ ^   ^   ^   ^   ^                           ^ ^                 N       N   N ^ N ^     ^ ^   N ^ ^         ^   ^   ^ ^   ^   ^   ^
                                                                                                                                                                                             ^   N     ^ ^   ^
         N   N   N   N   N   N   N   ^         ^     ^ ^ ^ ^   ^   ^   ^   ^                             ^                 ^   ^       N N ^ N   ^   ^     ^               ^ N ^ ^   ^   ^   ^   ^ N   ^ N   ^
         N   N   N   N   ^   ^   ^     ^   N N N N     ^ ^ ^   ^   ^   ^   ^       N                   ^ ^                 N   N N     N ^ ^ ^   ^ ^ N   N N N         N   ^ ^ ^ ^   ^   N   ^ N ^ N   ^   ^
         N   N   N   N   ^   N   ^   ^ N   N N N N N ^ ^ ^ ^   N   ^   ^   ^                           ^ ^                 N   N N     N ^ ^ ^   ^ N N   N ^ N       N ^   ^ ^ N N   N   ^   ^ ^ ^     ^   N ^
         N   N   N   N   N   N   ^   ^ ^   N N N N N N ^ ^ ^   N   ^   ^   ^                           ^ N                 N   N N     N N N ^   ^   N   ^ N ^       N N   ^ N ^ N   ^   N ^   N ^     N   ^ N
         N   N   N   N   ^   N   N   ^ N   N N N N N N N ^ ^   N   N   ^   ^                           N ^                 N     ^     N ^ N N     N N   N N N       ^ ^   N N ^ N   ^   ^ ^     N       N N ^
         N   N   N   N   N   ^   ^   N N   N N N N N N N ^ N   N   N   N   ^   ^                       N N                 N   N N     ^ ^ ^ ^   N N N   N N N         N   ^ N ^     ^   N ^               ^ ^
         N   N   N   N   ^   ^   N   ^ ^   N N N N N N N ^ N   N   N   N   N   ^       ^           N   ^ ^                 ^   N ^     ^ N ^ ^   ^ ^ N   N N ^       ^ N   N ^ N N   N   N N ^   ^ ^     N ^ ^
         N   N   N   N   ^   N   ^   ^ N   N N N N N N N N N   N   N   N   N   ^       ^   ^       N   ^ ^                 N   ^ N     ^ ^ N ^   N N N   N N         ^ N   ^ ^ N N   N   N N ^ ^ ^ ^   ^ N ^ ^
         N   N   N   N   N   N   ^   ^ N   N N N N N N N N N   N   N   N   N   ^   ^   ^   ^   ^   N   ^ ^                 ^   ^ N     N N N ^   N ^ N   N N ^       N N   N N N N   N   N N N ^ ^ ^   ^ N ^ N
         N   N   N   N   ^   N   ^   ^ ^   N N N N N N N N N   N   N   N   N   ^   ^   ^   N   N   N   ^ N                 N   ^ N     ^   N N   ^ N N   N   N       N ^       N N   ^   N ^ ^ N N ^   ^ N N N
         N   N   N   N   N   N   ^   N ^   N N N N N N N N N   N   N   N   N   ^   ^   ^   N   ^   N   ^ ^                 ^   N ^     N N N N     N N   N N N       ^ N   N ^   ^   N   ^ N     N ^   ^   ^
         N
         N
             N
             N
                 N
                 N
                     N
                     N
                         N
                         N
                             N
                             N
                                 N
                                 ^
                                     ^ N
                                     ^ ^
                                           N N N N N N N N N
                                           N N N N N N N N N
                                                               N
                                                               N
                                                                   N
                                                                   N
                                                                       N
                                                                       N
                                                                           N
                                                                           N
                                                                               ^
                                                                               ^
                                                                                   ^
                                                                                   ^
                                                                                       ^
                                                                                       ^
                                                                                           ^
                                                                                           N
                                                                                               N
                                                                                               ^
                                                                                                   ^
                                                                                                   ^
                                                                                                       N N
                                                                                                       ^ ^
                                                                                                                           ^
                                                                                                                           N
                                                                                                                               N N
                                                                                                                               N N
                                                                                                                                       N N N ^
                                                                                                                                       N ^ N ^
                                                                                                                                                 ^ N N
                                                                                                                                                   N ^
                                                                                                                                                         N N N
                                                                                                                                                         N N N
                                                                                                                                                                     ^
                                                                                                                                                                     N ^
                                                                                                                                                                           N N N N
                                                                                                                                                                           N N N N
                                                                                                                                                                                     N
                                                                                                                                                                                     ^
                                                                                                                                                                                         N N ^ N N
                                                                                                                                                                                         ^ ^ ^ ^ ^ N
                                                                                                                                                                                                       ^ N N ^
                                                                                                                                                                                                       N ^ N ^
                                                                                                                                                                                                                     5
True error matrix parameters




                        Reference class                                    Reference class
                     Natural Urban Crop Total                           Natural Urban Crop      Total
            Natural      226      27     74 327               Natural      25%     3%      8%    36%

                                                  Map class
Map class




             Urban        18     108     36 162                Urban        2%    12%      4%    18%
              Crop        89      36    286 411                 Crop       10%     4% 32%        46%
              Total      333     171    396 900                 Total      37%    19% 44%       100%
            Overall accuracy 69%     kappa 51%




                                                                                                        6
True error matrix parameters, graphical presentation




             True Map Land Cover area
                                                                                                    Natural
                                             37%               19%              44%                 Urban
True Reference Land Cover area
                                                                                                    Crop

                                        0%                        50%                     100%


                         Reference class                                    Reference class
                      Natural Urban Crop Total                           Natural Urban Crop      Total
             Natural      226      27     74 327               Natural      25%     3%      8%    36%

                                                   Map class
 Map class




              Urban        18     108     36 162                Urban        2%    12%      4%    18%
               Crop        89      36    286 411                 Crop       10%     4% 32%        46%
               Total      333     171    396 900                 Total      37%    19% 44%       100%
             Overall accuracy 69%     kappa 51%




                                                                                                         7
True error matrix parameters, graphical presentation



                                             36%               18%              46%
             True Map Land Cover area
                                                                                                    Natural
                                                                                                    Urban
True Reference Land Cover area
                                                                                                    Crop

                                        0%                        50%                     100%


                         Reference class                                    Reference class
                      Natural Urban Crop Total                           Natural Urban Crop      Total
             Natural      226      27     74 327               Natural      25%     3%      8%    36%

                                                   Map class
 Map class




              Urban        18     108     36 162                Urban        2%    12%      4%    18%
               Crop        89      36    286 411                 Crop       10%     4% 32%        46%
               Total      333     171    396 900                 Total      37%    19% 44%       100%
             Overall accuracy 69%     kappa 51%




                                                                                                         8
True error matrix parameters, graphical presentation
                             User's Accuracy                                                Producer's Accuracy
                             Reference class                                                  Reference class
                        Natural     Urban      Crop    Total                             Natural    Urban       Crop
             Natural       69%         8%      23%     100%                Natural          68%       16%        19%
Map class




                                                               Map class
              Urban        11%        67%       22%    100%                 Urban            5%       63%         9%
               Crop        22%         9%      70%     100%                  Crop           27%       21%        72%
                                                                             Total         100%      100%       100%
                                 Overall accuracy     69%            kappa              51%

                        User’s Accuracy                                                Producer’s Accuracy
            Crop                                                           Crop

        Urban                                                        Urban

    Natural                                                      Natural

                   0%                50%               100%                       0%                 50%               100%


                    kappa

   Overall accuracy                                                                                                     True


                            0%                                             50%                                         100%
                                                                                                                         9
True error matrix parameters, graphical presentation
                             User's Accuracy                                                Producer's Accuracy
                             Reference class                                                  Reference class
                        Natural     Urban      Crop    Total                             Natural    Urban       Crop
             Natural       69%         8%      23%     100%                Natural          68%       16%        19%
Map class




                                                               Map class
              Urban        11%        67%       22%    100%                 Urban            5%       63%         9%
               Crop        22%         9%      70%     100%                  Crop           27%       21%        72%
                                                                             Total         100%      100%       100%
                                 Overall accuracy     69%            kappa              51%

                        User’s Accuracy                                                Producer’s Accuracy
            Crop                                                           Crop

        Urban                                                        Urban

    Natural                                                      Natural

                   0%                50%               100%                       0%                 50%               100%


                    kappa

   Overall accuracy                                                                                                     True


                            0%                                             50%                                         100%
                                                                                                                        10
True error matrix parameters, graphical presentation
                             User's Accuracy                                                Producer's Accuracy
                             Reference class                                                  Reference class
                        Natural     Urban      Crop    Total                             Natural    Urban       Crop
             Natural       69%         8%      23%     100%                Natural          68%       16%        19%
Map class




                                                               Map class
              Urban        11%        67%       22%    100%                 Urban            5%       63%         9%
               Crop        22%         9%      70%     100%                  Crop           27%       21%        72%
                                                                             Total         100%      100%       100%
                                 Overall accuracy     69%            kappa              51%

                        User’s Accuracy                                                Producer’s Accuracy
            Crop                                                           Crop

        Urban                                                        Urban

    Natural                                                      Natural

                   0%                50%               100%                       0%                 50%               100%


                    kappa

   Overall accuracy                                                                                                     True


                            0%                                             50%                                         100%
                                                                                                                        11
In the real world, we do not know the true classification for all 900 pixels




                                                                     ?
           True (reference) population                               True error matrix




               ?
                                                                                            900




                                                                         Reference class




                                                                           Natural
                                                                           Urban
                                                                                     Crop
                                                       Map class
                                                                   Natural N          ^
                                                                   Urban
                                                                   Crop    ^



                                                                                                  12
In the real world, we do know the true classification for 30 sampled pixels




                                                                   ?
      Sample of (reference) population
          True true (reference) population                         True error matrix




                                                                                          900




                                                                       Reference class




                                                                         Natural
                                                                         Urban
                                                                                   Crop
                                                     Map class
                                                                 Natural N          ^
                                                                 Urban
                                                                 Crop    ^



                                                                                                13
In the real world, we do know the true classification for 30 sampled pixels




                                                                     ?
      Sample of true (reference) population                          True error matrix




                                                                                            900




                                                       Error matrix estimate from sample
                                                                            Reference class
                                                                         Natural Urban Crop Total
                                                                Natural        8      0       2   10




                                                    Map class
                                                                 Urban         0      4       2    6
                                                                  Crop         2      2      10   14
                                                                  Total       10      6      14   30
                                                                Overall accuracy 73%     kappa 58%
                                                                            Reference class
                                                                         Natural Urban Crop Total
                                                    Map class   Natural     27%      0%     7% 33%
                                                                 Urban       0%     13%     7% 20%
                                                                  Crop       7%      7% 33% 47%
                                                                  Total     33%     20% 47% 100% 14
In the real world, we do not know the true classification for all 900 pixels




• Let us leave the real world for the next 30
  minutes to compare
    – Known estimate of an error matrix with a sample
      of 30 pixels
    – Unknown true error matrix for all 900 pixels




                                                                               15
Comparison of true (unknown) error matrix with (known) sample estimate

                True (unknown) error matrix                     Error matrix estimate from sample
                           Reference class                                   Reference class
                        Natural Urban Crop Total                          Natural Urban Crop Total
               Natural      226      27    74 327                Natural        8      0      2    10
   Map class




                                                    Map class
                Urban        18     108    36 162                 Urban         0      4      2     6
                 Crop        89      36 286 411                    Crop         2      2     10    14
                 Total      333     171 396 900                    Total       10      6     14    30
               Overall accuracy 69%     kappa 51%                Overall accuracy 73%     kappa 58%




                                                                                                        16
Examples of random sampling error, simple random sample #1, sample size n=30
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           17
Examples of random sampling error, simple random sample #2, sample size n=30
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           18
Examples of random sampling error, simple random sample #3, sample size n=30
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           19
Examples of random sampling error, simple random sample #4, sample size n=30
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           20
Examples of random sampling error, simple random sample #5, sample size n=30
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           21
But how good is the sample estimate? Example, Producer’s Accuracy Urban
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%              50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           22
Example: Producers accuracy for urban
                   Area of each Land Cover Type
                         Sample Map Land Cover area
                            True Map Land Cover area                                                        Natural
                    Sample Reference Land Cover area                                                        Urban
                      True Reference Land Cover area                                                        Crop

                                                       0%                    50%                     100%

                                   User's Accuracy                                 Producer's Accuracy

                      Crop                                           Crop
                     Urban                                          Urban
                    Natural                                        Natural

                              0%              50%           100%             0%              50%            100%

                               kappa
                                                                                                            Sample
                    Overall accuracy
                                                                                                            True
                                       0%                              50%                                    100%




 Estimated Producer's Accuracy = 80%

    Crop
  Urban
                                                                                                                      `
 Natural

           0%                                                      50%                                                    100%


                                                                                                                                 23
Sample #1, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 80%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 24
Sample #2, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 71%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 25
Sample #3, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 60%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 26
Sample #4, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 53%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 27
Sample #5, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 70%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 28
Sample #6, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 73%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 29
Sample #7, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 88%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 30
Sample #8, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 60%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 31
Sample #9, n=60
                                                              Truth = 63%




                  Number of samples
                                      10



                                      5



                                      0
                                           0   20       40         60      80   100
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 40%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 32
Sample #10, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 45%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  33
Sample #11, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 67%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  34
Sample #12, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 86%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  35
Sample #13, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 75%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  36
Sample #14, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 73%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  37
Sample #15, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 47%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  38
Sample #16, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 57%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  39
Sample #17, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 64%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  40
Sample #18, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 70%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  41
Sample #19, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 67%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  42
Sample #20, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 77%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  43
Sample #21, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 67%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  44
Sample #22, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 76%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  45
Sample #23, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 100%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  46
Sample #24, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 90%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  47
Sample #25, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 50%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  48
Sample #26, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 77%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  49
Sample #27, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 91%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  50
Sample #28, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 40%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  51
Sample #29, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 27%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  52
Sample #30, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 55%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  53
Sample #31, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 56%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  54
Sample #32, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 78%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  55
Sample #33, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 40%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  56
Sample #34, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 71%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  57
Sample #35, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 83%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  58
Sample #36, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 62%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  59
Sample #37, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 64%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  60
Sample #38, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 88%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  61
Sample #39, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 57%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  62
Sample #40, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 56%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  63
Sample #41, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 57%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  64
Sample #42, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 73%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  65
Sample #43, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 40%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  66
Sample #44, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 55%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  67
Sample #45, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 63%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  68
Sample #46, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 71%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  69
Sample #47, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 55%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  70
Sample #48, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 67%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  71
Sample #49, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 77%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  72
Sample #50, n=60
                                                               Truth = 63%




                   Number of samples
                                       10



                                       5



                                       0
                                            0   20       40         60      80   100
                                                     % Producers Accuracy



 Estimated Producer's Accuracy = 89%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                 50%                          100%


                                                                                                  73
Truth = 63%
                                     300




                 Number of samples
                                     200



                                     100



                                      0
                                           0   20       40         60       80   100

True accuracy = 63%
                                                    % Producers Accuracy



 Estimated Producer's Accuracy = 78%

   Crop
  Urban
                                                                                       `
 Natural

           0%                                                50%                           100%


                                                                                                  74
In the real world, we do not know the true value

                                     300




                 Number of samples
                                     200



                                     100



                                      0
                                           0   20       40         60      80   100

True accuracy = 63%                                 % Producers Accuracy



 Estimated Producer's Accuracy = 78%

   Crop
  Urban
                                                                                      `
 Natural

           0%                                                50%                          100%


                                                                                                 75
In the real world, we do not know the true value, and we have only 1 sample




                 Number of samples
                                     10



                                     5



                                     0
                                          0   20       40         60      80   100
                                                   % Producers Accuracy



 Estimated Producer's Accuracy = 78%

   Crop
  Urban
                                                                                     `
 Natural

           0%                                               50%                          100%


                                                                                                76
Examples of random sampling error, simple random sample




• Any single sample estimate can differ from
  true error matrix from random sampling error
• Given our only sample with n=60, the
  estimated urban producers accuracy = 78%
  even though the true value is 63%
• However, the sample estimate is expected to
  equal the true value over all possible samples


                                                          77
Examples of random sampling error, simple random sample




• How can we improve reliability of estimate?
• What if sample size increased from n=60 to
  n=150?




                                                          78
Examples of random sampling error, simple random sample #51, sample size n=150
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           79
Examples of random sampling error, simple random sample #52, sample size n=150
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           80
Examples of random sampling error, simple random sample #53, sample size n=150
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           81
Examples of random sampling error, simple random sample #54, sample size n=150
Area of each Land Cover Type
      Sample Map Land Cover area
         True Map Land Cover area                                                        Natural
 Sample Reference Land Cover area                                                        Urban
   True Reference Land Cover area                                                        Crop

                                    0%                    50%                     100%

                User's Accuracy                                 Producer's Accuracy

   Crop                                           Crop
  Urban                                          Urban
 Natural                                        Natural

           0%              50%           100%             0%               50%            100%

            kappa
                                                                                         Sample
 Overall accuracy
                                                                                         True
                    0%                              50%                                    100%


                                                                                           82
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski
Fundamentals of accuracy_assessment_session2_czaplewski

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Fundamentals of accuracy_assessment_session2_czaplewski

  • 1. Session 2 Fundamentals of Accuracy Assessment Raymond L Czaplewski United States Forest Service Rocky Mountain Research Station Fort Collins, Colorado USA 1
  • 2. Session 2 Topics • Different sample designs – Simple Random Sampling (Systematic Sampling) – Stratified Random Sampling • Different sample survey estimators • Different sample sizes, n=30, 60, 150 • How close are estimates to true value? • Example of a 30×30 = 900 pixel world 2
  • 3. Hypothetical “real world” True (reference) population N N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N ^ N N N ^ N ^ ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N N N N ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ ^ N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N ^ N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Reference class N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 30×30 = 900 pixels ^ ^ Natural N N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Urban Crop N N N N ^ ^ ^ ^ N N N N ^ ^ ^ ^ ^ ^ ^ N ^ ^ N N N N ^ N ^ ^ N N N N N N ^ ^ ^ ^ N ^ ^ ^ ^ ^ N N N N N N ^ ^ ^ N N N N N N ^ ^ ^ N ^ ^ ^ ^ N N N N N ^ N N ^ N N N N N N N N ^ ^ N N ^ ^ N ^ N ^ N N N N N ^ ^ N N N N N N N N N ^ N N N N ^ ^ N N N N N N ^ ^ N ^ ^ N N N N N N N ^ N N N N N ^ ^ N ^ ^ N N N N ^ N ^ ^ N N N N N N N N N N N N N N ^ ^ ^ N ^ ^ N N N N N N ^ ^ N N N N N N N N N N N N N N ^ ^ ^ ^ ^ N ^ ^ N N N N ^ N ^ ^ ^ N N N N N N N N N N N N N ^ ^ ^ N N N ^ N N N N N N N ^ N ^ N N N N N N N N N N N N N ^ ^ ^ N ^ N ^ ^ N N N N N N N ^ N N N N N N N N N N N N N N ^ ^ ^ ^ N ^ N N N N N N N N ^ ^ ^ N N N N N N N N N N N N N ^ ^ ^ N ^ ^ ^ ^ 3
  • 4. Hypothetical remotely sensed thematic map model for this “real world” Map #1 N N N ^ N ^ N ^ ^ ^ ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ N N ^ N N ^ N ^ N ^ ^ N ^ ^ N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N ^ N ^ ^ N ^ N ^ N ^ ^ ^ ^ N ^ ^ ^ N ^ ^ N ^ N N ^ N ^ ^ N N N ^ N ^ ^ ^ ^ N N ^ N ^ ^ ^ ^ ^ ^ ^ N N N ^ N ^ N N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ N ^ ^ ^ N N N ^ N N N ^ ^ ^ ^ N ^ ^ N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ N N N N N ^ ^ N N ^ ^ ^ N ^ ^ ^ ^ N N N ^ ^ ^ N N ^ ^ N ^ N N ^ ^ ^ ^ ^ ^ N ^ ^ N ^ N N N N ^ N ^ ^ ^ ^ N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ ^ ^ N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ ^ ^ ^ N N N ^ N ^ ^ ^ ^ N ^ ^ N ^ ^ N ^ ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ N ^ N N N N ^ ^ ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N ^ ^ ^ N ^ N ^ N ^ N N ^ ^ ^ N ^ ^ ^ ^ ^ N ^ ^ ^ ^ N N ^ N N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 30×30 = 900 pixels N ^ ^ ^ ^ ^ N N ^ N ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ N ^ N ^ N N N N ^ ^ ^ ^ ^ N N N N N ^ ^ ^ ^ ^ N ^ N ^ N ^ ^ N N N N ^ ^ ^ ^ N N N ^ N N ^ ^ ^ N N N ^ ^ ^ ^ ^ N ^ Map class N N N N N N ^ ^ N ^ N ^ N N ^ N ^ N ^ N ^ N ^ N ^ N N ^ N ^ N N N N N N N ^ ^ N N ^ N ^ ^ ^ N N N ^ Natural N N N N ^ ^ ^ ^ N N N N N N N ^ N ^ ^ N ^ ^ ^ Urban ^ N ^ ^ N ^ ^ ^ ^ N N N ^ ^ N N ^ N N N N N ^ ^ ^ N ^ ^ N ^ N ^ ^ N ^ N N N N N ^ N ^ ^ N N N N N ^ ^ ^ ^ ^ N ^ ^ Crop ^ ^ ^ N N N N ^ N ^ N N N ^ N N N N N N N N N N ^ ^ ^ ^ N ^ N N ^ N ^ N N ^ N N N N N ^ N N ^ N ^ ^ N N ^ ^ N N N ^ N ^ N N N N N N N N N ^ N N ^ ^ N ^ N N ^ ^ ^ ^ N N N N N ^ ^ N N N N N ^ N N N N N N N ^ N N ^ N N ^ N N N N ^ N ^ N ^ N N N N ^ N N N N ^ ^ ^ ^ ^ ^ N N ^ N ^ 4
  • 5. Remotely sensed thematic Map #1 True Error Matrix Error matrix presented by Steve Stehman Reference class Natural Urban Crop Total Traditional Analysis: Error Natural 226 27 74 327 Map class (Confusion) Matrix Urban 18 108 36 162 Reference Land Cover Crop 89 36 286 411 Mapped Natural Urban Crop Total Total 333 171 396 900 Natural 0.25 0.03 0.08 0.36 Overall accuracy 69% kappa 51% Urban 0.02 0.12 0.04 0.18 Reference class Crop 0.10 0.04 0.32 0.46 Natural Urban Crop Total Natural 25% 3% 8% 36% Map class Total 0.37 0.19 0.44 Urban 2% 12% 4% 18% Crop 10% 4% 32% 46% Total 37% 19% 44% 100% True (reference) population Map #1 N N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ N ^ N ^ ^ ^ ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N ^ N N ^ N ^ N ^ ^ N ^ ^ N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N ^ N N ^ N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N ^ N ^ 30×30 = 900 pixels N N N ^ N ^ ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N ^ N ^ N ^ N ^ ^ ^ ^ N ^ ^ ^ N ^ ^ N ^ N N ^ N ^ ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N N ^ N ^ ^ ^ ^ N N ^ N ^ ^ ^ ^ ^ ^ ^ N N N ^ N ^ N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N N N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ N ^ ^ ^ N N N ^ N N N ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ ^ ^ ^ N ^ ^ N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ N N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N N N ^ ^ N N ^ ^ ^ N ^ ^ ^ ^ N N N ^ ^ ^ N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ ^ N N ^ ^ N ^ N N ^ ^ ^ ^ ^ ^ N ^ ^ N ^ N N N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ N ^ ^ ^ ^ N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ ^ ^ N N N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N N ^ N ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N ^ ^ ^ ^ N N N ^ N ^ ^ ^ ^ N ^ ^ N ^ ^ N N N ^ N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N N ^ ^ ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ N ^ ^ ^ N ^ N ^ N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ N N ^ ^ ^ N ^ ^ ^ ^ ^ N ^ ^ ^ ^ N N ^ N N N N ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N N ^ N ^ ^ ^ N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N ^ ^ ^ N N N N N N N ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ N N ^ N ^ ^ ^ ^ N ^ ^ ^ ^ ^ ^ N ^ N ^ N N N N ^ ^ ^ ^ N N N N ^ ^ ^ ^ ^ ^ ^ N ^ ^ N N N N ^ ^ ^ ^ ^ N N N N N ^ ^ ^ ^ ^ N ^ N ^ N ^ ^ N N N N ^ N ^ ^ N N N N N N ^ ^ ^ ^ N ^ ^ ^ ^ ^ N N N N ^ ^ ^ ^ N N N ^ N N ^ ^ ^ N N N ^ ^ ^ ^ ^ N ^ N N N N N N ^ ^ ^ N N N N N N ^ ^ ^ N ^ ^ ^ ^ N N N N N N N ^ ^ N ^ N ^ N N ^ N ^ N ^ N ^ N ^ N ^ N N N N N ^ N N ^ N N N N N N N N ^ ^ N N ^ ^ N ^ N ^ N ^ N N N N N N N ^ ^ N N ^ N ^ ^ ^ N N N ^ N N N N N ^ ^ N N N N N N N N N ^ N N N N ^ ^ N N N N N ^ ^ ^ ^ N N N N N N N ^ N ^ ^ N ^ ^ ^ N N N N ^ ^ N ^ ^ N N N N N N N ^ N N N N N ^ ^ N ^ ^ ^ N ^ ^ N ^ ^ ^ ^ N N N ^ ^ N N ^ N N N N N ^ ^ ^ N ^ ^ N N N N ^ N ^ ^ N N N N N N N N N N N N N N ^ ^ ^ N ^ ^ N ^ N ^ ^ N ^ N N N N N ^ N ^ ^ N N N N N ^ ^ ^ ^ ^ N ^ ^ N N N N N N ^ ^ N N N N N N N N N N N N N N ^ ^ ^ ^ ^ N ^ ^ ^ ^ N N N N ^ N ^ N N N ^ N N N N N N N N N N ^ ^ ^ ^ N ^ N N N N N ^ N ^ ^ ^ N N N N N N N N N N N N N ^ ^ ^ N N N ^ N N ^ N ^ N N ^ N N N N N ^ N N ^ N ^ ^ N N ^ ^ N N N N N N N N N ^ N ^ N N N N N N N N N N N N N ^ ^ ^ N ^ N ^ ^ ^ N ^ N N N N N N N N N ^ N N ^ ^ N ^ N N ^ ^ ^ N N N N N N N N N N N N N ^ ^ N ^ ^ N N N N N N N N N N N N N N N N N N N N N N N N N N ^ ^ ^ ^ ^ ^ ^ N N ^ ^ ^ N N ^ ^ ^ N N N N N N N N ^ N ^ N ^ ^ N N N ^ N N N N N N ^ N ^ N N N N N N N N N ^ N N ^ N N ^ ^ ^ ^ ^ N ^ N N ^ N ^ N ^ 5
  • 6. True error matrix parameters Reference class Reference class Natural Urban Crop Total Natural Urban Crop Total Natural 226 27 74 327 Natural 25% 3% 8% 36% Map class Map class Urban 18 108 36 162 Urban 2% 12% 4% 18% Crop 89 36 286 411 Crop 10% 4% 32% 46% Total 333 171 396 900 Total 37% 19% 44% 100% Overall accuracy 69% kappa 51% 6
  • 7. True error matrix parameters, graphical presentation True Map Land Cover area Natural 37% 19% 44% Urban True Reference Land Cover area Crop 0% 50% 100% Reference class Reference class Natural Urban Crop Total Natural Urban Crop Total Natural 226 27 74 327 Natural 25% 3% 8% 36% Map class Map class Urban 18 108 36 162 Urban 2% 12% 4% 18% Crop 89 36 286 411 Crop 10% 4% 32% 46% Total 333 171 396 900 Total 37% 19% 44% 100% Overall accuracy 69% kappa 51% 7
  • 8. True error matrix parameters, graphical presentation 36% 18% 46% True Map Land Cover area Natural Urban True Reference Land Cover area Crop 0% 50% 100% Reference class Reference class Natural Urban Crop Total Natural Urban Crop Total Natural 226 27 74 327 Natural 25% 3% 8% 36% Map class Map class Urban 18 108 36 162 Urban 2% 12% 4% 18% Crop 89 36 286 411 Crop 10% 4% 32% 46% Total 333 171 396 900 Total 37% 19% 44% 100% Overall accuracy 69% kappa 51% 8
  • 9. True error matrix parameters, graphical presentation User's Accuracy Producer's Accuracy Reference class Reference class Natural Urban Crop Total Natural Urban Crop Natural 69% 8% 23% 100% Natural 68% 16% 19% Map class Map class Urban 11% 67% 22% 100% Urban 5% 63% 9% Crop 22% 9% 70% 100% Crop 27% 21% 72% Total 100% 100% 100% Overall accuracy 69% kappa 51% User’s Accuracy Producer’s Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Overall accuracy True 0% 50% 100% 9
  • 10. True error matrix parameters, graphical presentation User's Accuracy Producer's Accuracy Reference class Reference class Natural Urban Crop Total Natural Urban Crop Natural 69% 8% 23% 100% Natural 68% 16% 19% Map class Map class Urban 11% 67% 22% 100% Urban 5% 63% 9% Crop 22% 9% 70% 100% Crop 27% 21% 72% Total 100% 100% 100% Overall accuracy 69% kappa 51% User’s Accuracy Producer’s Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Overall accuracy True 0% 50% 100% 10
  • 11. True error matrix parameters, graphical presentation User's Accuracy Producer's Accuracy Reference class Reference class Natural Urban Crop Total Natural Urban Crop Natural 69% 8% 23% 100% Natural 68% 16% 19% Map class Map class Urban 11% 67% 22% 100% Urban 5% 63% 9% Crop 22% 9% 70% 100% Crop 27% 21% 72% Total 100% 100% 100% Overall accuracy 69% kappa 51% User’s Accuracy Producer’s Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Overall accuracy True 0% 50% 100% 11
  • 12. In the real world, we do not know the true classification for all 900 pixels ? True (reference) population True error matrix ? 900 Reference class Natural Urban Crop Map class Natural N ^ Urban Crop ^ 12
  • 13. In the real world, we do know the true classification for 30 sampled pixels ? Sample of (reference) population True true (reference) population True error matrix 900 Reference class Natural Urban Crop Map class Natural N ^ Urban Crop ^ 13
  • 14. In the real world, we do know the true classification for 30 sampled pixels ? Sample of true (reference) population True error matrix 900 Error matrix estimate from sample Reference class Natural Urban Crop Total Natural 8 0 2 10 Map class Urban 0 4 2 6 Crop 2 2 10 14 Total 10 6 14 30 Overall accuracy 73% kappa 58% Reference class Natural Urban Crop Total Map class Natural 27% 0% 7% 33% Urban 0% 13% 7% 20% Crop 7% 7% 33% 47% Total 33% 20% 47% 100% 14
  • 15. In the real world, we do not know the true classification for all 900 pixels • Let us leave the real world for the next 30 minutes to compare – Known estimate of an error matrix with a sample of 30 pixels – Unknown true error matrix for all 900 pixels 15
  • 16. Comparison of true (unknown) error matrix with (known) sample estimate True (unknown) error matrix Error matrix estimate from sample Reference class Reference class Natural Urban Crop Total Natural Urban Crop Total Natural 226 27 74 327 Natural 8 0 2 10 Map class Map class Urban 18 108 36 162 Urban 0 4 2 6 Crop 89 36 286 411 Crop 2 2 10 14 Total 333 171 396 900 Total 10 6 14 30 Overall accuracy 69% kappa 51% Overall accuracy 73% kappa 58% 16
  • 17. Examples of random sampling error, simple random sample #1, sample size n=30 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 17
  • 18. Examples of random sampling error, simple random sample #2, sample size n=30 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 18
  • 19. Examples of random sampling error, simple random sample #3, sample size n=30 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 19
  • 20. Examples of random sampling error, simple random sample #4, sample size n=30 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 20
  • 21. Examples of random sampling error, simple random sample #5, sample size n=30 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 21
  • 22. But how good is the sample estimate? Example, Producer’s Accuracy Urban Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 22
  • 23. Example: Producers accuracy for urban Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% Estimated Producer's Accuracy = 80% Crop Urban ` Natural 0% 50% 100% 23
  • 24. Sample #1, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 80% Crop Urban ` Natural 0% 50% 100% 24
  • 25. Sample #2, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 71% Crop Urban ` Natural 0% 50% 100% 25
  • 26. Sample #3, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 60% Crop Urban ` Natural 0% 50% 100% 26
  • 27. Sample #4, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 53% Crop Urban ` Natural 0% 50% 100% 27
  • 28. Sample #5, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 70% Crop Urban ` Natural 0% 50% 100% 28
  • 29. Sample #6, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 73% Crop Urban ` Natural 0% 50% 100% 29
  • 30. Sample #7, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 88% Crop Urban ` Natural 0% 50% 100% 30
  • 31. Sample #8, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 60% Crop Urban ` Natural 0% 50% 100% 31
  • 32. Sample #9, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 40% Crop Urban ` Natural 0% 50% 100% 32
  • 33. Sample #10, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 45% Crop Urban ` Natural 0% 50% 100% 33
  • 34. Sample #11, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 67% Crop Urban ` Natural 0% 50% 100% 34
  • 35. Sample #12, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 86% Crop Urban ` Natural 0% 50% 100% 35
  • 36. Sample #13, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 75% Crop Urban ` Natural 0% 50% 100% 36
  • 37. Sample #14, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 73% Crop Urban ` Natural 0% 50% 100% 37
  • 38. Sample #15, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 47% Crop Urban ` Natural 0% 50% 100% 38
  • 39. Sample #16, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 57% Crop Urban ` Natural 0% 50% 100% 39
  • 40. Sample #17, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 64% Crop Urban ` Natural 0% 50% 100% 40
  • 41. Sample #18, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 70% Crop Urban ` Natural 0% 50% 100% 41
  • 42. Sample #19, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 67% Crop Urban ` Natural 0% 50% 100% 42
  • 43. Sample #20, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 77% Crop Urban ` Natural 0% 50% 100% 43
  • 44. Sample #21, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 67% Crop Urban ` Natural 0% 50% 100% 44
  • 45. Sample #22, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 76% Crop Urban ` Natural 0% 50% 100% 45
  • 46. Sample #23, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 100% Crop Urban ` Natural 0% 50% 100% 46
  • 47. Sample #24, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 90% Crop Urban ` Natural 0% 50% 100% 47
  • 48. Sample #25, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 50% Crop Urban ` Natural 0% 50% 100% 48
  • 49. Sample #26, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 77% Crop Urban ` Natural 0% 50% 100% 49
  • 50. Sample #27, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 91% Crop Urban ` Natural 0% 50% 100% 50
  • 51. Sample #28, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 40% Crop Urban ` Natural 0% 50% 100% 51
  • 52. Sample #29, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 27% Crop Urban ` Natural 0% 50% 100% 52
  • 53. Sample #30, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 55% Crop Urban ` Natural 0% 50% 100% 53
  • 54. Sample #31, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 56% Crop Urban ` Natural 0% 50% 100% 54
  • 55. Sample #32, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 78% Crop Urban ` Natural 0% 50% 100% 55
  • 56. Sample #33, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 40% Crop Urban ` Natural 0% 50% 100% 56
  • 57. Sample #34, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 71% Crop Urban ` Natural 0% 50% 100% 57
  • 58. Sample #35, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 83% Crop Urban ` Natural 0% 50% 100% 58
  • 59. Sample #36, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 62% Crop Urban ` Natural 0% 50% 100% 59
  • 60. Sample #37, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 64% Crop Urban ` Natural 0% 50% 100% 60
  • 61. Sample #38, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 88% Crop Urban ` Natural 0% 50% 100% 61
  • 62. Sample #39, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 57% Crop Urban ` Natural 0% 50% 100% 62
  • 63. Sample #40, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 56% Crop Urban ` Natural 0% 50% 100% 63
  • 64. Sample #41, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 57% Crop Urban ` Natural 0% 50% 100% 64
  • 65. Sample #42, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 73% Crop Urban ` Natural 0% 50% 100% 65
  • 66. Sample #43, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 40% Crop Urban ` Natural 0% 50% 100% 66
  • 67. Sample #44, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 55% Crop Urban ` Natural 0% 50% 100% 67
  • 68. Sample #45, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 63% Crop Urban ` Natural 0% 50% 100% 68
  • 69. Sample #46, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 71% Crop Urban ` Natural 0% 50% 100% 69
  • 70. Sample #47, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 55% Crop Urban ` Natural 0% 50% 100% 70
  • 71. Sample #48, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 67% Crop Urban ` Natural 0% 50% 100% 71
  • 72. Sample #49, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 77% Crop Urban ` Natural 0% 50% 100% 72
  • 73. Sample #50, n=60 Truth = 63% Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 89% Crop Urban ` Natural 0% 50% 100% 73
  • 74. Truth = 63% 300 Number of samples 200 100 0 0 20 40 60 80 100 True accuracy = 63% % Producers Accuracy Estimated Producer's Accuracy = 78% Crop Urban ` Natural 0% 50% 100% 74
  • 75. In the real world, we do not know the true value 300 Number of samples 200 100 0 0 20 40 60 80 100 True accuracy = 63% % Producers Accuracy Estimated Producer's Accuracy = 78% Crop Urban ` Natural 0% 50% 100% 75
  • 76. In the real world, we do not know the true value, and we have only 1 sample Number of samples 10 5 0 0 20 40 60 80 100 % Producers Accuracy Estimated Producer's Accuracy = 78% Crop Urban ` Natural 0% 50% 100% 76
  • 77. Examples of random sampling error, simple random sample • Any single sample estimate can differ from true error matrix from random sampling error • Given our only sample with n=60, the estimated urban producers accuracy = 78% even though the true value is 63% • However, the sample estimate is expected to equal the true value over all possible samples 77
  • 78. Examples of random sampling error, simple random sample • How can we improve reliability of estimate? • What if sample size increased from n=60 to n=150? 78
  • 79. Examples of random sampling error, simple random sample #51, sample size n=150 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 79
  • 80. Examples of random sampling error, simple random sample #52, sample size n=150 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 80
  • 81. Examples of random sampling error, simple random sample #53, sample size n=150 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 81
  • 82. Examples of random sampling error, simple random sample #54, sample size n=150 Area of each Land Cover Type Sample Map Land Cover area True Map Land Cover area Natural Sample Reference Land Cover area Urban True Reference Land Cover area Crop 0% 50% 100% User's Accuracy Producer's Accuracy Crop Crop Urban Urban Natural Natural 0% 50% 100% 0% 50% 100% kappa Sample Overall accuracy True 0% 50% 100% 82