glc 2000 “final results” workshop 24-26 march 2003 land cover mapping at global scale: some...
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GLC 2000 “final results” workshop 24-26 March 2003
Land cover mapping at global scale: some lessons learnt from
the GLC 2000 project
E. Bartholomé
JRC-Ispra
GLC 2000 “final results” workshop 24-26 March 2003
Some observations on the following issues
• Properties of input data
• Pre-processing
• Classification procedures and cover type identification
• The way forward
GLC 2000 “final results” workshop 24-26 March 2003
Input data
• Number of channels(more channels would be better: cloud mask, LC discrimination)
• Radiometry(OK)
• Atmospheric correction(Cloud mask, aerosols)
• Geometry(Sub-pixel accuracy: the real difference)
• Data format(Global coverage in one single image)
GLC 2000 “final results” workshop 24-26 March 2003
Pre-processing
• How to build syntheses– 3rd min albedo (Cabral & al)– Average (Vancutsem & al)– BRDF correction (Champeaux & al)– Cloud mask (Viaux & al., Cherlet & al.)
• How to clean temporal profiles– Low vegetation coverage (Defourny & al.)– Removal of atmospheric noise (Bartholomé & al)
• Good strategic choice not to wait for improved methods, but to directly start map production (last data received March 2001, this workshop March 2003)
• But results obtained through labour intensive techniques difficulty to repeat regularly
GLC 2000 “final results” workshop 24-26 March 2003
Classification
• Most people have used from-the-shelf classification software– Classical approach: 1) divide space according to spectral
properties, 2) label each area with reference information
• Ideally, the structural properties of each land cover class should have to be identified form space capacity to measure a number of parameters:– Vegetation height for each strata– Vegetation cover for each strata (forest cover fcover)– Vegetation type (woody/grassy/…, broadleaf / needle leaf)– seasonality
GLC 2000 “final results” workshop 24-26 March 2003
Classification
• At least two cases of ad hoc classification algorithm– Small water bodies (VGT only, semi arid
regions only)– Urban areas (VGT + DMSP)
GLC 2000 “final results” workshop 24-26 March 2003
Next steps – medium term
• Combination of existing LC map with new data to identify possible changes
• Multi-sensor database to complete the spectrum of measurements
• Intensification on priority land cover classes to respond to specific needs (i.a. forest, agriculture, protected areas,…) – use of medium resolution
GLC 2000 “final results” workshop 24-26 March 2003
Next steps – medium term
We should consider LC mapping & monitoring at global scale as a component of environmental monitoring:Technical commonality between several
applications (e. g.Forest change & FCCC/KP, Agriculture & food security, protected areas & CBD, wetlands & Ramsar conv.)
Incorporate indicators of disturbances possibly leading to land cover conversion / degradation (e. g. fire, burn scars, drought index, surface water, etc…)
GLC 2000 “final results” workshop 24-26 March 2003
Next steps – long run
• Need to incorporate specifications related to land cover monitoring into future space missions– Choice of instruments / wavebands / repeat cycle,
etc.– Quality of output data (e. g. geometry)
• Need for research to develop new approaches to retrieve significant LC-related parameters (e. g. BRDF parameters as indicators of vegetation structure)
GLC 2000 “final results” workshop 24-26 March 2003
The end !