7.3.2 Slant range to ground range correction to minimize scale differences

Slant versus Ground Range

An F5/F3 stereo pair is shown in slant range presentation. The images can be manually rotated with respect to each other in order to eliminate differences in orientation caused by the descending and ascending passes. The slant range presentation causes distortions in scale between the two images. The opposite side stereo configuration results in resolution differences. The most compressed near edges will be on the outer edge of the stereo pair, while the least compressed far edge is at the centre of the stereo-model. This means the same land features are resolved differently. This is particularly evident when the shorelines are examined. There is a great variation in shape between the two images. As a result of the slant range presentation and the opposite side stereo configuration, only small local areas of this image pair can be viewed in stereo.

This image pair is also difficult to view in stereo because there is very little elevation difference to perceive.

It is easier to see the stereo effect in Stereo pair 17 (than in Stereo pair 16). This is due to the ground range presentation of the image pair. But once again, rotation is still necessary for a better depth perception over a larger area . As these images are of flat terrain, the stereo effect is noticeable at the boundary between water and land. A slight slope leads down to the water's edge.

Radiometrically, both image pairs (16 and 17) show a very strong contrast between land and water, road network and surroundings on each image. There is very little variation between the images. Seasonal differences in vegetation are visible since there is a two-month difference between images.