--- Start of Idrisi List message Hello everyone, I am a GIS novice...I hope someone can help me sort out a little problem... I would like to be able to calculate the distance that all pixels in a DEM are, in terms of flow length, away from a stream. I guess it is a bit like the RUNOFF module, except in reverse, and with the stream as a source image. Something very similar to this is sometimes referred to as Flow Path Length. How can I do this with a minimum of fuss in Idrisi32? I have tried to fudge it using an anisotropic cost surface (VARCOST and DISPERSE) using a 'reversed' aspect direction image and a image of the stream as a source image but the results I am getting just aren't right (the catchment has an unusual shape). I suppose I could isolate each of the sub-catchments and use the point of the catchment outlet as a source image, but the process seems fairly cumbersome, especially for a newbie like me, when there are so many sub-catchments emanating from the stream. Am I looking at this the right way? Can anyone help me with a recipe for producing this Flow Path Length map? Please excuse my ignorance and thank you very much in advance for any advice. Monte. --- End of Idrisi List message IDRISI-L is an unmoderated list. As a service to list users, please post a summary of useful responses to your questions. To post a message to IDRISI-L, send it to [EMAIL PROTECTED] To subscribe to the list, send an email from the address to be subscribed to [EMAIL PROTECTED] with "subscribe" (without quotes) as the first line of the message body. To unsubscribe, do the same, only with "unsubscribe" as the first line of the message body.