If I have a large structure (say 20m wide by 150 m long) I know that I can get good accuracy along the short side but how do I take the images to get the long side with the same accuracy?
 
If I can't get far enough away from the 150m long side to see it in one photo then what is the best way to calibrate five images that are pans from one short side to the next?
 
Imagine you are an ant and you want to do a bus, that sort of photo shoot?

Hello,
for this the best is to use a software like REALVIZ Stitcher. You stitch 4-5 pictures of your long wall together, you make a planar render and you import this stitched picture into ImageModeler taking care of setting the right focal length calculated in Stitcher's render (.cam file) into ImageModeler new camera setting.