Obviously MOIDS VI products are corrected (to some extents) for cloud shadows. But how about topographic shadows? If yes, any information on DEM and methodology used for corrections?
If no, to what extent do you think VIs (particularly NDVI) in C5 are affected by topography and illumination/viewing geometry? As far as the general appearance of the vegetation cover is concerned, my focus is not on "trees", but mostly on grass, shrubs, and subshrubs. Can I also have some suggestions from your own experiences with correcting topographic, viewing/illumination effects on NDVI?
The MOD13 product is corrected for angular variations in observation and sun-target-sensor variations but not due to topography using a DEM (I believe). It is also important to note that there has occurred a significant degradation of the Terra MODIS sensor affecting VI data. See Wang et al. (2012) Remote Sens. Environ., 119.
Dear Mojtaba,
You can find essential information in theme in the transactions of my colleagues Drs Anatolii. Shutko, Alexander Chuclanttsev. My own experiience in your aspect was: experiremental stuties of correlations between the topographic relief and the surface water content over the rice-growing areas in the Krasodar oblast, But these materials have been published and now are remaining only in Russian.
The MOD13 product is corrected for angular variations in observation and sun-target-sensor variations but not due to topography using a DEM (I believe). It is also important to note that there has occurred a significant degradation of the Terra MODIS sensor affecting VI data. See Wang et al. (2012) Remote Sens. Environ., 119.
Dear
The tpographic shadows are not addressed, as well directional effects.
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