Hi serhat, The GCP and coregistration files are optional so if you do not have them, you should be able to proceed with generating an interferogram in SARscape, just leaving those fields blank. The shift parameter file is an output file that the interferogram generation step will create. You just need to enter a name to give that file. In general, it's a good idea to check the SARscape Help, which will give you brief definitions of each input parameter, and let you know whether they are required or optional. - Peg

hi peg, thank you for your attention and your fast response. as a matter of fact that i'm not as well as you in this respect :) (answer in 10 minutes) ok, your info is great for me and you say true -i forgot to check sarscape help. help is nice but a little bit insufficient. as you can guess, i'm an insar enthusiast and coming another question from me: dem generation or dem extraction -actually i don't know what the diffrence is between both of them. whatever, i want to create a dem file to generate interferogram. i found sarscape > dem extraction > tools > dem extraction > srtm-3 v2. as far as i understand, sarscape software can download srtm data. sarscape help says that "Reference file list Input file(s) name of the image to be used as geographic reference for the Digital Elevation Model extraction. This file is mandatory if the cartographic co-ordinates are not specified." so, if i specify co-ordinates, reference file list is not mandatory -like optional. ok, now, i want to learn how the format of co-ordinates is. i wrote like this: west: -112 east: -111 north: 36 south: 35 but a warning came from software "check the parameters"... did i make a mistake in co-ordinates' format or did i understand false (reference file is optional???) a little confused :( i'm asking for an instruction from you to figure out this puzzle. how can i use srtm data to generate dem for creating interferogram? a little example will be explanatory for me. thanks in advance. kind regards, serhat