The Radarsat data products for which incidence angle can be calculated would be those in slant range or ground range, not already georeferenced products. You need to have a product in slant or ground range, with all of the associated information about sensor geometry, to calculate incidence angle. If you made an incidence angle image from a slant or ground range R1 image, then you could georeference that using image to image or image to map tools from ENVI. I would think that if you already had a georeferenced verson of the R-1 data, then an image-to-map registration would be possible, picking tie points from the georeferenced and slant/ground range data. - Peg Exelis VIS