CORRECTION OF BRDF-EFFECTS IN VEGETATION INDICES USING SIMULATED SENTINEL-2 DATA

摘要

Monitoring of vegetation canopies during the growingrnseason requires a frequent temporal coverage to observernrapid changes. Sentinel-2 features a revisit timernof only 5 days using two satellites with a large swathrnwidth of 290 km due to an increased field of view ofrn21°. This leads to images whose pixels are stronglyrninfluenced by varying acquisition geometry affectingrnthe results of vegetation indices as well as derivedrnbiophysical parameters. In this paper a concept isrnpresented for the normalisation of BRDF-influencedrnSentinel-2 vegetation index values of arable crops.rnDetailed knowledge of the BRDF as well as of thernvegetation index distribution function (VIDF, VIDF =rnVI (BRDF)) of the observed canopies is required that isrnmodelled by a spectral, spatial and temporal simulationrnsystem. The normalisation is done by transforming offnadirrninto nadir vegetation index values based onrnempirical analyses of the modelled VIDFs.