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 !