The Stereo Pair Inversion Tool is an Adobe Photoshop plug-in which can create a heightmap representing the three dimensional data of a scene from two coplanar photographs of a scene.
The algorithm requires two images perfectly parallel to each other and a small distance apart. The simplest way to achieve this with one camera is to use a tripod on a flat, level surface. Move the tripod sideways without rotating the assembly between shots. Larger objects and structures will be less sensitive than smaller ones to errors in camera position but all sizes of scenes will be affected by changes in camera orientation between pictures, so be especially careful to not rotate or change the pitch of the camera.