We can digitally convert single Landsat scenes (and other space imagery) into pseudo-stereo by merging the Landsat pixels with registered DEM data. Then we can manipulate that scene into view pairs having different parallax. Consider this left-right example in Morocco:

Astronauts using the Large Format Camera (LFC) on Space Shuttle Mission 41-G, in October, 1984 (and subsequently), at an altitude of about 300 km (186 mi) snapped (pre-planned and targets of opportunity) 2,160 black and white and color/color-IR photos (see Section 12). The photos comprise a 23 cm by 46 cm (9.2 by 18.4 inches) area, with ground resolutions between 14 m and 25 m (46-82 ft). Taking these in quick succession allows along track forward overlap of between 20% and 80%, from which we attain excellent stereo viewing, at a B/H of about 1.2. View the two LFC strips, cut from such a pair, that cover the Panamint Mountains and Death Valley in eastern California. The European Space Agency has flown a similar Metric Camera.

Adapted from T.E. Avery and G.L. Berlin, Fundamentals of Remote Sensing and Airphoto Interpretation, 5th Ed., Fig. 5-12, © 1992. Reproduced by permission of Macmillan Publishing Company, Indianapolis, IN.

11-19: Which is higher: the mountains near the top or those towards the bottom? ANSWER

The two High Resolution Visible (HRV) scanners on the SPOT satellites (see Section 3) can tilt sidewards up to 27° in either direction. Not only does this tilting permit wider coverage during a single pass (one of the HRV scanners can stay in the vertical mode), but we can combine the off-nadir view with another view (either on- or off-nadir) taken on another date to give rise to a stereo pair. We show a plateau on the Libyan/Tunisian border below from a panchromatic mode stereo pair acquired on February 23, and 25, 1986, at an off-nadirs angle of 24°E (right image) and and 10°W (left image).

11-20: Where is the plateau: at the bottom or the top of the photo? ANSWER

For those who want to see a striking stereo pair in color, taken by SPOT about 3 1/2 weeks apart, showing the Great Rift Valley of Kenya (note the step fracture zones), we have linked these (Top = Left) (Bottom = Right), which you can choose to print on your color printer to examine, either under a stereoscope or with your unaided vision. Again, you may have to move one or both until some segment in common to each is in proper position to induce the stereo effect.

Visible-IR scanners and SAR imagers are now flying on spacecraft such as ERS-1 and ERS-2, JERS-1, and Radarsat, among others. Laser and radar altimeters are planned for future flights. One prime task is to gather global sets of data that have a wide variety of topographic applications. An ultimate goal is to fill the current gaps in mapping the Earth's land surface at more informative scales. A second objective is better resolution profiles and elevation models of sea states within the major ocean bodies.

Collaborators: Code 935 NASA GSFC, GST, USAF Academy
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