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I want to know how to find the nos. of scene of stereo CARTISAT-1 data required to prepare DEM of an area(say 84000 sq km)? any suggestion/solution/calculation?

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well obviously you need two images for stereo. Then you have to calculate the overlapping area of both images and then divide 84000 Km2 by the overlapping area of two images. This should give you the number of stereo scenes (two images) that are required theoretically. However, you need to specify the AOI and see if the image footprints cover your area. Do you mean the Indian CARTOSAT-1?

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I'm assuming that you are talking about the Cartosat-1 aft & Fore scenes. NRSC sells this data, with each pair covering an area of 27.5 km x 27.5 km. so assuming that the overlap is 100%, each pair will cover an area of 756 sq km. so you will require at-least 111 pairs.

However, have you actually checked the data availability from the NRSC portal? It is accessible at:

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Stereo pairs usually don't have 100% overlap, it is more likely in the 40-60% range, maybe 75% if lucky. So, 111 pairs is indeed the minimum, but it will likely take a bit more. – Baltok Nov 6 '12 at 15:38
correct, I was just doing a back of the envelope calculation; Hence I used the phrase "at-least 111 pairs" – Devdatta Tengshe Nov 6 '12 at 16:17
@Baltok I do not know Cartosat specifically, but most very high resolution satellite sensor provide stereo images with an overlap that is close to 100%. The 40-60% range is for aerial frame cameras. – radouxju Sep 22 '15 at 19:57
@radouxju Good point! I was thinking more from an aerial stereo pairs standpoint, so if satellite stuff has a greater overlap, then Devdatta's estimate may indeed be quite close. – Baltok Sep 22 '15 at 22:41

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