"Nice work on image stitching with PTGUI. As commented above it works pretty well with a limited number of images taken over flat terrain. If you need to work with hundreds or thousands of images taken over varying topography you'll need a…"
As Steve suggested photogrammetric block adjustment is the solution to decrease field work to minimum. You don't need accurate XYZ for the camera position, just initial guesses that are allowed to be meters or tens of meters off the true…"