The Viking Landers have two eyes and therefore can view the landscape in three dimensions, just as we do with our own eyes. However, presentation of stereoscopic pairs has been a frustrating problem. Because the camera separation is almost 1 m, objects close to the spacecraft are viewed with orientation equivalent to that for an object at the tip of one's nose. The pictures have to be carefully rectified so that the relative scales remain the same throughout the scene. The distance between the images must be controlled to permit optimum fusion.
Some persons can appreciate the stereoscopic effect much more easily than others.
There is, however, one fairly reliable guide to the viewer's success. Wait a few minutes and you will hear an exclamation of surprise and wonder. Then you will know he has seen it. The effect is so unusual, literally drawing you into the scene, that very few people come upon it without excitement. On the following pages we present 19 stereopairs.