Dr Jerome O Connell - presentation made at various conferences throughout Europe as part of PhD which was funded by the EPA under the STRIVE Research Programme 2007-2013 (2007-PhD-ET-2)

1. A Change Detection Tool for
Vegetation Disturbance on Irish
Peatlands
SPIE Remote Sensing
2011
Jerome O Connell, Nick Holden, John Connolly
Biosystems Engineering
University College Dublin
Ireland

2. Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)
Introduction• Peatlands
– Peatlands: 4-6% land surface: over 33% soil carbon stock
– Peatlands cover ~20% of Ireland
– Over 85% of Irish peatlands disturbed
– Need for RS based change detection process for Irish
peatlands
• RS based change detection process
– Multispectral
• Optimum spatial, spectral and temporal resolution
– Multi temporal
• Peatlands can be dynamic
• Disturbance seasonal and inter-seasonal
– Multi platform
• Over 78% cloud cover in summer, 82% in winter
• Project Outline
– 5 sites, 3 assessed to-date
• Kerryhead (Commonage)
– Upland Heath (642 ha)
– Burning, conversion to pasture
• Slieve Bloom Mountains (SPA)
– Blanket Bog (3845 ha)
– Drainage, peat extraction, burning, afforestation,
bog bursts
• Clara (SAC)
– Raised Bog (460 ha)
– Drainage, peat extraction, burning
– Data
• > 240GB of multispectral data
• 10 to 30m resolution
• SPOT 2, 4 and 5; Landsat TM, ETM+, Aster VNIR, IRS P6
LISS
• Auxiliary data
– MODIS, Ikonos, Kompsat, Quickbird, aerial
photography, habitat maps, disturbance records.

3. 0.00
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TIC
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Normalised6s
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TIC
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Normalised6s
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TIC
6s
Normalised6s
Methods
• Pre-processing
– Geo-rectification to master image
• RMSE 0.25
– DN to TOA reflectance to EVI2
• Atmospheric scattering: DOS (mean from
lowest 5% of pixels)
• Cloud mask (unsupervised)
• Topographical normalisation
• Automated in Spatial Modeller
– TIC normalisation
• Density slicing
• Regional growth tool
• Urban and water
– Cross calibration
• Difference images (5% ± mean)
• Water urban, peatland and conifer pixels
• Random sampling for regional growth tool
• Change detection
– Spatial Modeller
• Image differencing
• Spatial threshold
• Spectral threshold
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)

4. Cross Calibration
• Pixel Extraction
– Difference image
• ± 5% change
– Spectral threshold
• ± 0.015 EVI2
– Spatial threshold
• 300 – 1000 pixels
• Validation
– Histograms
• Before
• After
– Statistics
• Mean, SD
• Kolmogorov Smirnov (KS) Test
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)
D = 0.63 D = 0.08
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.2 0.4 0.6 0.8 1
Count
EVI2
Slieve Bloom
Histograms
TM
TM Cross Cal
Master

5. Model Calibration
• Clara Bog
– Burn in April 2008
(35.93ha)
• SD Threshold Analysis
– 0.5 SD = 4.47% error
– 1.0 SD = 5.31% error
– 1.5 SD = 0.19% error
– 2.0 SD = 3.70% error
– 2.5 SD = 24.08% error
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)

6. Model Validation
• Error matrices
– Random sampling
• Approx 1 point/ 2ha
– Ground truth data
• OSi aerial photos
• Ikonos, Kompsat
– Validation of 1.5 SD for
optimum user, producer,
overall and Kappa.
– High omission (Producer)
of Change at > 1.5 SD
– High commission (User) of
Change at < 1.5 SD
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)

7. Slieve Bloom Change
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)
Conlawn Hill
Glenlahan
Valley
Spot4_2003_04_18
Spot4_2004_06_14
Spot4_2006_04_05 Spot5_2007_06_07
Spot5_2010_06_20
Spot2_2009_06_03

8. Conclusions
• Negative and positive change assessed
– Disturbance indicated by initial increase (vegetation
removal) and post disturbance decrease (re-
colonisation of non-native species)
• Success of image TIC normalisation and cross
calibration
– Typically 0.05± EVI2
• To date, error matrices have given high (> 80%)
Kappa values at 1.5 SD
• Use of Erdas spatial models combined with batch
processing – potential to process large databases
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)
Kerryhead Change Detection
2000 to 2010

9. Further Work
Funded by the EPA, STRIVE under the National Development Plan (2007 – 2013)
• Assess the detection accuracy of various disturbance types
• Verify change detection model in other sites
– Ground based LAI data
• Sun elevation may still be an issue <16°
– Hill shade overlay
• Non-spatial ground truth data
– Slieve Bloom and Wicklow Mountains
Acknowledgements
• Environmental Protection Agency under STRIVE program
• National Parks and Wildlife Service / Coillte
• European Space Agency (Cat 1)
• CNES (ISIS)
• OSi