Hi Agus, no I mean the RemoteSensing package https://r-forge.r-project.org/projects/remotesensing/ Cheers
>>> Agustin Lobo <alobolis...@gmail.com> 19.01.2012 11:26 >>> Matteo, by "RemoteSensing package" you mean the landsat package? Agus 2012/1/18 Matteo Mattiuzzi <matteo.mattiu...@boku.ac.at>: > > Dear Vikram, > > It is not good to calculate NDVI from DN. The purpose of DN (digital > number) is only for packing as much information as possible into a given > âBIT-sizeâ (in Landsat 8-bit/pixel/band). > DN is practically the radiance (I think TOA?) modified with an offset > and a gain in order to press or expand the range between 0 and 255. > This means that the relation between bands is changed, and this is a > crucial need for NDVI (and generally for indices). > Probably the minimum pre-processing you absolutely need to do is the > conversion from DN to RADIANCE (TOA) using the gain and bias information > in the MTL file (metadata). Better and more precise is to calculate the > ground reflectance. I did this with the RemoteSensing package on > R-Forge. But the current version doesn't work because of incomplete > modifications in the package code. > > Non-vegetated areas can have positive values. I think the soil has > often a NDVI of 0.1. Clouds sometimes have even 0.2 as...anyway you > can't trust a NDVI from DN and you can't sharply differentiate > veg/nonVeg by positive or negative ndvi values. Water normally has a > clear negative NDVI (~-0.2). > > Also implemented in the RemoteSensing package are functions to compute > other vegetation indices, I did not test them but maybe you can find > something useful there (type â?ndviâ after installing and loading the > package). > > Cheers Matteo > > > > >>>> Vikram Ranga <babuaw...@gmail.com> 1/18/2012 10:49 am >>> > Hello list, > I am working with landsat images and would like to create a > phenological > cycle with NDVI. > I am using R for that but NDVI values changes if i use on sensor > reflectance instead of DN values i.e. giving different result in every > case. > I tried to compare histograms seems to have changed and I am not > getting > negative values where there is no vegetation but if i use DN values it > > gives negative values to such locations. Do anybody have any idea what > > went wrong?? > > Thanks in advance and would be much appreciated. > > Vikram > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > [[alternative HTML version deleted]] > > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > [[alternative HTML version deleted]]
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