If i understand your problem correctly, you need two pieces of information: 1) An image containing your concentrations that also has map info - sounds like you have this already. 2) Some way to identify the specific lat/lon's for the political boundaries, regions, etc.for which you want to extract a total concentration. There are many ways to get this info, but a pretty common way would be a vector file - a shapefile, EVF, etc. If you have a shapefile that contains the boundaries you need and you want to do this programmatically, you might want to have a look at this tech tip: http://www.ittvis.com/ser...echtip.asp?ttid=4196 If you just want to use the ENVI GUI, then your process will probably be to convert the vector coverage to an ROI, then do image operations on that ROI (band math, etc.). If you describe more exactly what data formats you're working with, people can probably chime in with a little more specific help. Jeff