Could anyone explain why the vegetation indices are not working in the desert region?
I used Landsat 8 image which has been already radiometric/atmospheric corrected.
I want to see the fractional vegetation cover in super arid environment in part of middle east country. Most of the area is covered by sand sheet, but there has a few trees and I wish I could extract them.
So far, NDVI, SAVI, and EVI seems not working well. NDVI and SAVI output are quite similar, and somehow both have high value in some place which do not have any vegetation at all (blue circles in the image below). In contrast, the area contain a few trees has lower value (red circle). Only the value seems matching with real land cover types is agricultural area which shows in red colour.
The SAVI image below is displayed as a rainbow scale, from low (-1): dark blue to high (+1): red.