[Addendum] Hamish: > > (not talking about pan-sharpening, but in general,) > > how about the situation where you have a map data > > which is loudly dominated by a signal, and you want to try and remove that > > loud signal so that you can look at the subtle variations caused by a > > different source that the loud signal had been masking?
Nikos: > Yes, this _can_ be a perfect use-case. > Especially if the presence of the feature in question, is in at least one or > in some of the input dimensions near/close to zero. This last statement is > based on Pielou's (flawless explanation of how PCA works) [1] and own > experiences [2]. If the above holds true (near-zero projection, in one or some dimensions, of the features of interest), and in some way, these "subtle variations" do form distinct clusters, I'd be keen to try out non-centered PCA and (re-)confirm Pielou and myself (claiming, for example, higher Producer's accuracies as in --my-- burned area mapping). Nikos > A separation/isolation attempt of the feature in question from dominant > variances will be "supported". The "loud" signal would be channeled among > the first few PCs and the "subtle variations" _could_ then be more evident > in some of the higher order components. > All in all, one has to look at the numbers -- drawing conclusions from the > PC images is not safe! [...] _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
