>The first CORONA satellites had a single camera, but a two-camera system was quickly implemented.[40] The front camera was tilted 15° aft, and the rear camera tilted 15° forward, so that a stereoscopic image could be obtained
There are different ways to do it, that's one of them.
A lot of the techniques were first used with airplanes, then later with satellites. Lots of overlap because planes allowed for easier localization and better resolution, especially earlier on in remote sensing.
I've done this from a plane before and got some very epic 3D images. I think Mt. Rainier at sunset was one of the best. So yeah, the easy way if your camera is on a moving platform, is take a shot, count three aligators, then take another shot.
