London Meeting, April 1998 - home page
Stereogrammetric mapping of
Mars
Paul M. Schenk (schenk@lpi3.jsc.nasa.gov)
& Brian Fessler
Lunar & Planetary Institute, 3600 Bay Area Blvd., Houston,
TX 77058, USA.
The Viking Orbiters acquired quality stereo coverage of a significant
fraction of Mars in 1976-1980. Several groups have been using this
stereo coverage to produce global and regional scale topographic maps of
Mars. The LPI group has been using these data to map the topography
of specific geologic structures and landforms. Our software uses
scene-recognition to map parallax to 1/5th pixel (being upgraded to 1/10th
pixel) precision. It also allows us to automatically trim our DEM
data on the basis of height error or correlation coefficient (of the scene
matching). Manual editting is also performed. On some targets
(e.g., Ganymede and Mercury), virtually no clean up is required.
Like Io, however, Mars is plagued by featureless deposits and photometric
and seasonal variability (in the case of Mars due to long time lags between
images). This results in significant gaps in our DEM maps in some
locations. Viking stereo quality (convergence angle, resolution)
also varies wildly over the surface Mars, however. One of our projects
focused on debris aprons, which have not been previously mapped topographically.
We find that these aprons can be 300 to 1 km thick, thicker than has been
generally assumed, and have surface slopes of 1 to 10 degrees. These
data are robust but like all Mars topography data suffer from an unreliable
global datum. While stereo-derived DEM can provide higher spatial
resolution than altimeter data, they degrade seriously when smooth featureless
terrain is mapped and at present cannot be reliably 'controlled.'
This problem will be solved by MOLA. Stereo- and altimeter-derived
topography thus compliment each other very effectively to solve specific
geologic problems on Mars. A dedicated high-resolution stereo mapping
camera should be a high priority for later Mars missions in the current
Mars exploration program.
Extra-terrestrial
Mapping Home Page
Comments to Dr. Randy Kirk
This page updated: 28 January, 2002, by Mark
Rosiek
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