Influence of angular effects and adjustment on medium resolution sensors for crop monitoring

Remote sensing imagery at medium spatial resolution (30-60m) like Landsat and AWiFS have been widely used in mapping crop types and monitoring crop conditions. Angular effects from wide swath remote sensing data have been observed. This paper examines the influence of angular effects on surface reflectance of typical surface and crop types for both narrow swath (e.g. Landsat) and wide swath (e.g. AWiFS) sensors. A bi-directional reflectance distribution function (BRDF) look-up table (LUT) for surface types from cropland data layer (CDL) was established. A LUT-based approach is proposed to correct angular effects for crops and natural vegetations. The angular corrected reflectance will provide a consistent data source for crop condition monitoring and longterm time-series analysis.