How does google map put together satellite pictures?
This certainly is a signal processing question albeit a little vague. I can't say for certain that Google use it but the SIFT (shift invariant feature transform) algorithm http://www.cs.ubc.ca/~lowe/keypoints/ has been used in variant form in technologies such as Microsoft's Photosynth. It allows key features of multiple images containing overlapping content (supject to arbitrary X,Y,Z shifts) to be registered and matched. In simple terms...very clever image stitching.  The link provides all the paper references to the original algorithm. For another example of such technology check out this lecture about photosynth > http://www.ted.com/talks/blaise_aguera_y_arcas_demos_photosynth.html