I think you will find that all your image processing topics in IDL's manual 'Image Processing in IDL'. On the 'Contents' page of IDL's Online Help see particularly: For questions on mapping 3D image data to 2D and vice versa: User's Guides -> Image Processing in IDL -> Transforming Image Geometry and User's Guides -> Image Processing in IDL -> Mapping an Image onto Geometry For working with image amplitudes: User's Guides -> Image Processing in IDL -> Transforming Between Domains I think the chapter subheadings in this manual are intuitively named, and you should be able to find your exact topics pretty quickly. If you need more help, I will look out for your Reply, but you should give very exact specifics on what kind of data you are starting with, and what exact data you are hoping to either a) extract from it, or b) transform it to. James Jones