Hey my first post here and a newbie to the envi enviroment also... What i want to do is try to compare "alos palsar images" (plain images), the images are separated by time and sometimes they dont overlap perfectly. The comparison should be on the difference between db before cutting and after cutting... via a simple thresholding algorithm. This would preferably generate a vector (or raster) outlining the edges of what can be identified as clear cuts. This would then be compared against actual polygons drawn from SPOT and aerial photographs used as reference when identifying clear cuts. Im a little bit stuck in how to proceed after getting the images properly georeferenced and generating an image that contains data in decibels and also making an overlay of the vectorlayer...? Any help would be appreciated and of course quouted in the thesis im working on.