Map work calculations

1. MAP-WORK CALCULATIONS
MR. MOTSAPI
18 SEPTEMBER 2017

2. LESSON OBJECTIVES
• Learners should be able to calculate:
1. Gradient
2. Actual distance
3. Area
4. Speed/ distance/ time

3. LESSON OBJECTIVES
5. Bearing and Magnetic declination

4. 1. GRADIENT
• Gradient is the steepness of slope.
• You can easily see on a topographic map whether a slope is
steep or gentle.
• When contour lines are close to each other it is a steep slope
and when contour lines are far apart it is gentle slope.

5. GRADIENT

6. • Gradient is shown in a
fraction format e.g.1:8
• 1 represents the vertical
distance (1m change in
height).
• 8 represents the horizontal
distance (8m change with
distance).

9. • Height difference between X
and Y.
• X is 2140m and Y is 2320m
• NB always subtract the bigger
number from the smaller
number
• DH: 2320m - 2140m = 180m
• For distance you multiply the
map distance by map scale.
• D= map distance × map scale
• = 72mm × 0,5 km
• = 3600m

10. • Gradient = ℎ𝑒𝑖𝑔ℎ𝑡 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 (𝑚)
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑚)
• =
180𝑚
3600𝑚
• =
180÷ 180
3600÷ 180)
• =
180𝑚
3600𝑚
=
1
20
• =1:20

11. 2. DISTANCE
• Measure the distance in millimeters.
• You can convert the map distance into the real distance by
using the following formula.

13. WHAT IS THE REAL DISTANCE IN KM?
• Distance =
𝑀𝐴𝑃 𝐷𝐼𝑆𝑇𝐴𝑁𝐶𝐸× 𝑆𝐶𝐴𝐿𝐸
1000 000
• =
124mm×50 000
1000 000
• = 6.2 Km
• NB: remember, if you had give your answers in meter you must
divide your answer by 1000

14. 3. AREA
• To calculate area of a given place, you need to use 2 distance
calculations.
• Convert each side in kilometers before using the distance
formula.

15. AREA = LENGTH ×BREATH
Length
L =
155mm×50 000
1000 000
= 7,75Km
Area= length × breath
= 7,75km × 7,75km
= 60,063 km2
Breath
B =
155mm×50 000
1000 000
=7,75km

16. 4. SPEED/ DISTANCE/ TIME

17. • If you walk from V to W at an average speed of 5km/h. how
long will it take to cover the distance?
Firstly, you calculate the distance between the two points.
Secondly, apply it to the formula.

18. D =
93mm×50 000
1000 000
= 4,65km
Time =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒
𝑠𝑝𝑒𝑒𝑑
=
4,65km
5 𝑘𝑚/ℎ
= 0,93h
= 0,93 × 60
= 55 minutes 48 seconds

19. 5. BEARING AND MAGNETIC DECLINATION
• Bearing refers to the degrees between two points.
• 0 degrees is always at the top or true north.
• Always measure the angle in a clockwise direction from 0
degrees.
• Magnetic declination/ direction refers to the compass direction.

21. MAGNETIC DECLINATION/ DIRECTION
• Is the difference between magnetic north and true north.
• Magnetic declination changes from year to year.
• Change can be from east (angle becomes smaller), change can
also be from west (angle becomes bigger)
• Change to west you add
• Change to east you subtract

24. REFERENCES
• Fensil, D. (2010). Map work Calculations. Available from:
https://www.slideshare.net/fenslin/mapwork-
calculations?qid=afb3811f-e388-4a7f-b4bc-
b2a5207740f3&v=&b=&from_search=1. [Accessed on18
September 2017].
• Bonner, T. (2012). An introduction to teaching scale
measurement in Geography. Available from:
https://www.slideshare.net/tbonnar/social-studies-
geography-skills-scale. [Accessed on 18 September 2017].

25. • Noeleen, M. (2012). Scale and Distance. Available from:
https://www.slideshare.net/noeleenleahy/scale-and-distance-
13921381. [Accessed on 18 September 2017].
• Bonner, T. (2012). An introduction to teaching scale
measurement in Geography. Available from:
https://www.slideshare.net/tbonnar/social-studies-
geography-skills-scale. [Accessed on 18 September 2017].