Title

Sub-pixel Mapping of Croplands in China: Using Multi-temporal VEGETATION Sensor Data and Spectral Mixture Analysis

Abstract

Over the last few decades large-scale mapping and monitoring of agriculture has primarily been dependent upon the remotely sensed data from the NOAA AVHRR sensors at 1-km spatial resolution. At 1-km spatial resolution, however, the land surface is mostly a mixture of various land cover types, including vegetation, soil and water. Early studies that explored uses of spectral mixture analysis and AVHRR data for quantification of percent fractional cover within a pixel have had limited success, primarily because AVHRR has too few spectral bands. In this study, we explored the potential of the VEGETATION (VGT) sensor on the SPOT 4 satellite for sub-pixel mapping of agriculture in China. VGT represents one of a new generation of optical sensors designed for enhanced observation of land and vegetation. VGT has 4 spectral bands: blue (430-470 nm), red (610-680 nm), near-infrared (780-890 nm), and mid-infrared (1580-1750 nm); and it provides daily global coverage at 1-km spatial resolution. Multi-temporal 10-day composites of VGT data from March 1999 to May 1999 were used for spectral mixture analysis to derive four endmembers (cropland, forest, water and urban/soil) in eastern China. Fractional cropland estimates from the VGT-based spectral mixture analysis were evaluated using (1) point-level land cover data from field surveys in 2000, (2) landscape-level cropland data derived from digital classification of a Landsat TM image acquired in 1996; (3) province-level agricultural field survey data from the early 1980s; and (4) province-level cropland data derived from visual interpretation of Landsat TM images acquired in 1995/1996. The preliminary results show that VGT data are very useful for sub-pixel mapping of agriculture in China. This study provides a sound basis to explore daily VGT data in 2000 for sub-pixel mapping of agriculture at the country to continental scales, as part of our contribution to the VEGA2000 Initiative effort.

Publication Date

5-2001

Journal Title

Joint Assembly Meeting, American Geophysical Union

Publisher

American Geophysical Union Publications

Document Type

Conference Proceeding