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.