I made a mosaic of aerial images of the island of Saipan from 10 images shot by the military in 1945. The mosaic worked but the images don't match up well at the edges. This is most obvious with roads and other straight lines. I used 30-50 reference points per image and a few different algorithms. I settled for a first degree algorithm because the individual images looked less distorted at the edges with that one.
1. How can I get the edges to match up ie, be continuous from one image to another? I tried dividing the images into smaller areas but the smaller areas don't provide enough referencing points to make a good mosaic.
2. How many reference points and which algorithm would be best for this effort: first degree, second degree or one of the others?
3. The images overlap closer in flat areas than on hilly and mountainous ones even though the images, I assume, were taken from directly above. Does that make sense in this context?
4. Unrelated to mosaics but how do you suggest I make the ocean the same value?