Notes on making a stitched panorama with a 100,000' balloon-cam
Caleb sends us an article, "Wherein I present the results of and detail the technical feats needed to stitch together imagery from six cameras into interactive fully spherical imagery and video taken from a balloon sent up to nearly 100,000 feet. (*phew*)"
There are some other factors that come into play with panorama stitching. You want to avoid placing control points on objects that move between images taken. Typical panoramas are done with one camera being rotated after each photo is taken. Objects that move between photos taken that have control points on them will severely hinder the stitching process.
You also want to avoid placing control points on objects at largely different distances from the lens. Don’t mix control points between objects a couple feet away and a hundred feet away as the optimizer won’t be able to make them fit to one transform. I’m able to mostly ignore this issue at very high altitudes as everything is so far away that the difference between the closer and the further objects is so slight that it doesn’t do much to negatively impact the optimization. Of course, that means I don’t allow any control points to be placed on anything attached to the camera payload, including the parachute and the balloon.
In order to place control points you have to have common features. That’s why you need the overlap between images. The more overlap the better the result. In the sample images above we have one image, the fourth, that isn’t able to be connected to any of the others. And it’s not because there’s no overlap. There are three issues with the fourth image that presents us from finding control points in it.