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Stereoscopic Principle involves 2 (or more) images of the same object captured from DIFFERENT positions. for presition is very importante the Base/Heigth ratio (Base: distance between images; heigth: Distance from image to object) In classic aerial photogrammetry a good B/H ratio round 0.6 The case of multiple "Very High Resolution satellite imagery (not stereo)" cited by intertronic, could obtain poor results due B/H ratio. Modern Photogrammetric techniques adresses ray-cloud photogrammetry, that (in very simplified words) involve several images of the same object (and several correlations), but this is not apllicable yet to satellite images. Aster images offers a good B/H ratio, (I belive is close to 0.6, but not sure). Process is relatively simple in some softwares. But I don't recall any modeule to do this in ArcGIS: Good option for software for this are: PCI Geomática, ASTER DTM (for ENVI); ENvi with DTM module, Erdas. You can also download ASTER DEM Products from the web. Final TIP: The use GCPs (Ground Control Points) IS VERY IMPORTANT. If you can't afford get them on field with a GPS (differential GPS), you can donwnload a Envi processed Image and a DEM, so use some ponts from that dataset. Regards Art