Hi, I am a very new user toying around with various idl tools. I created a surface using isurface, importing a file with latitude(y), longitude(x) and elevation data(z). My task is to find out the surface area and the volume. I found those very features in the operations -> statistics option : Area under surface: 32400.0000, Approximate volume: 20352106496.0000. Now my questions are : 1. What do the above mentioned statistics signify? Have they counted the number of non-white voxels to give the volume? Is this a 3D image? If so can I somehow save the surface in a 3D image format and count the no. of voxels to get the same result myself? 2. The distance between longitudes varies a lot from the equator to the poles. So by my simplistic treatment in iSurface I must be getting an approximate volume that is very different from the actual volume. I think one solution is to get a weighted sum of the no. of voxels (assuming that i can take the 3D image as an input to a program) where the weight = surface distance per 10 change in latitude * surface distance per 10 change in longitude at the latitude,longitude of the voxel. Is there a better solution or maybe an in-built option idl that deals with such latitude-longitude-elevation plots?? Am i completely on the wrong track to solve this problem??