There are two approaches I could use. One is to mount two identical cameras on the aircraft, either across the width or along the length. On my biggest plane, I could get them about 3 meters apart on the wingtips. It's a pretty big model

The other one is, as suggested, to simply use images taken at the desired separation in time, from the one camera. With a 5 Hz update GPS, and typical flying speeds of around 60MPH or less, I can get accurate spacings down to less than a meter, essentially the error on the gps.

The problem with both methods, although arising from slightly different reasons, is with rotation between the images. In the second case, the aircraft has to fly in a dead straight line relative to the ground, or the images fit along either a curve (if it's turning) or a slanted line (in the case of crosswinds). Of course both simultaneously are possible.

In the first case, if the aircraft is yawing about it's center axis, the two images will be rotated relative to each other.

It also needs to maintain constant altitude above sea level. All this really ultimately needs to be automated, which is simple enough. An autopilot can fly a raster scan pattern ensuring the images overlap by any necessary amount, using gps coordinates to trigger the camera at points equally spaced in distance rather than time. Doing it manually, from the ground, is fairly difficult.

The end result would be pictures with exact x,y,z coordinates known, as well as field of view, roll, pitch and yaw data, and lens data allowing the images to be corrected geometrically. One desired outcome is the ability to tile these images together to form a much larger one at very high resolution, as is done with a pan-tilt mount to make spherical or cylindrical panoramas. Although in this case is is a flat projection, since the camera position is moving in a plane rather than just rotating.

The other outcome is to process the data to build a decent-resolution digital elevation map of the ground. This data could be used to improve the autopilot, so it knows how far away the ground based simply on position and absolute altitude.

It could also be used to drape the mosaic image over, giving a nice 3d image of the area that it's flying over. From there it's a short step to have it make Battlefield 2 maps

pca