Land cover analysis at a regional scale exploiting low and medium resolution ENVISAT ASAR Data: Application to Poyang Lake Area (Jianxi Province, P.R. China)

Located in Jiangxi Province, Poyang Lake is the largest freshwater lake in China and constitutes a major hydrological subsystem of the middle Yangtze river (Changjiang) basin in central China. An impressive amount of low to medium resolution ENVISAT data covering the Poyang Lake's 2004 and 2005 hydrologic years were acquired and analysed within the framework of the flood DRAGON project. Land cover mapping was realized synergistically using: 1) a land cover map derived from a colour composition containing seasonal ENVISAT ASAR Global Monitoring Mode image sums, and; 2) a land cover map derived from a colour composition containing filtered, seasonal ENVISAT ASAR wide swath mode image sums. Confronted and validated with the hydrodynamic characterization derived from Landsat reference data, these preliminary classifications lead to a land cover map with 13 classes covering 20,000 km2 (170 km from north to south and 120 km from East to West) and was realized at a 1/200 000 scale, but can be used from 1/150 000 to 1/500 000. The results highlight the great potential of ASAR medium and low resolution products for wide-area mapping. Worldwide, large archives of such data already exist which should enable access to the prerequisite amount of data required for such large-scale, land cover characterization.