COMPACT AIRBORNE SPECTROGRAPHIC IMAGER (CASI) USED FOR MAPPING LAI OF CROPLAND

摘要

During the BOReal Ecosystem-Atmosphere Study (BOREAS), which took place in Saskatchewan and Manitoba in 1994 and 1996, the Compact Airborne Spectrographic Imager (CASI) acquired images of different surfaces including croplands and boreal forests. In this paper, we present an analysis of CASI data against ground measurements of leaf area index (LAI) for croplands. Processed individual CASI bands from different crops and fields are combined and show that: (1) the blue band reflectance of cropland decreases with LAI; (2) the red band reflectance shows a weaker and more scattered decreasing trend with LAI than the blue band; and (3) the near-infrared (NIR) band reflectance reaches a plateau at a LAI of one. It is also shown that the response of vegetation indices based on the red and NIR bands, such as the Normalised Difference Vegetation Index (NDVI), to LAI is weak, although the Simple Ratio shows a stronger, but more scattered, linear increase with LAI than the NDVI. Comparisons with similar studies of vegetation indices and LAI for cropland and forested areas are presented.