Hi aariel22, Do you know what type of processing you would like to do to detect the leads in sea ice from the ERS-1 data? If you only need to look at the imagery, and perhaps identify pixels with values below a certain threshold (i.e., dark pixels), then you can certainly do that in ENVI without SARscape. The definition of sigma nought requires the calculation of the incident angle, which is affected by the terrain. If your area is perfectly flat, then I suppose you could create an image that has values of zero everywhere, and call that your DEM.Just keep in mind that if that perfectly flat DEM at sea level is not a correct representation of the actual elevation in any part of your image, the sigma nought values you calculate there will also not be accurate. There are some radar tutorials that you may find useful on the Exelis VIS web site at: https://www.exelisvis.com/ProductsServices/ENVI/Tutorials.aspx#radar - Peg