Photography/optical lens distortion/surveying. Please move to appropriate forum. I wish to survey an area of a friend's backyard using overhead photos. I can get photos from about 25 feet up a TV antenna with a digital SLR that has a 14-42mm lens. The area to be surveyed is 70'x20' and is about 10' from the tower. That makes for a lot of foreshortening. (see diagram). I've done lots of pano / stitch shots before of landscapes and such, but in those cases the correcting for angular disortion wasn't a priority. It was enough that they stitched together seamlessly. In this case, I want to eliminate all angular distortion (using PhotoShop). i.e. a 2'x2' square at the edge of the final image needs to BE a square (not foreshortened into a diamond) and it needs to be the same SIZE as the same square in the centre of the image. I thought I could simply take enough pics and stitch them together, compensating for distortion between pics but (and here is the crux of my problem) I am finding that there is distortion within each pic (I'll call it "intra-pic distortion"). i.e. two squares in the same pic will not be congruent. No matter how much I distort any given pic, I cannot eliminate ditortion at two points simultaneously (if I make one is square, the other will be a diamond and vice versa). How can I fix this? I learned in college that a 50mm lens is nearest human vision. Can I set the lens to 42mm and hopefully eliminate this ... intra-pic distortion? Thoughts?