Planetary geodesy and cartography at the USGS, Flagstaff: Moon, Mars, Venus, and beyond

An important theme of our work is the synergistic use of a variety of geodetic, cartographic, and photogrammetric software packages. The USGS digital cartographic software system ISIS provides most of the processing capability needed for planimetric mapping tasks such as our revision of the global digital image mosaic of Mars (MDIM).  The geodetic control network on which this mosaic is based was produced at RAND with planetary bundle-block adjustment software that was developed there and that has recently been transferred to the USGS where we are also using it to compute a revised control network of Io from Voyager and Galileo images.  The revised MDIM compiled in 2000 is substantially improved over the version produced from the same ~4500 Viking Orbiter images in 1991, both in geodetic accuracy and in radiometric/cosmetic quality.  Maps of the Galilean satellites of Jupiter have also been improved geodetically and cosmetically as we have added Galileo images to the control networks and digital mosaics. 

Stereotopographic mapping of the Moon, Mars, Venus, and the asteroid Eros requires ISIS for data ingestion and calibration steps, along with the commercial photogrammetric software SOCET SETâ for “photogrammetric” steps such as adjustment of control and topographic model extraction and editing.  Novel procedures must frequently be developed to deal with problems of planetary datasets such as the need to use large numbers of small images, nonuniform image coverage, poor image overlap, and lack of true ground control.  Some sensors, such as the Magellan Synthetic Aperture Radar (SAR) and Mars Global Surveyor Mars Orbiter Camera (MOC), also require the development of specialized sensor model software.

A second important theme is the complementarity between photogrammetric techniques and the laser altimeter systems coming into increasing use on planetary spacecraft.  Stereoanalysis of Clementine images of the Moon has been used to fill in major gaps in the altimeter dataset at high latitudes, but the stereo data must be tied to the altimetry where the datasets overlap.  For Mars and Eros, our stereomapping provides spatial sampling of topography finer than that achieved by altimetry, but use of the altimetry data for vertical control is essential to improve the absolute accuracy of photogrammetric topographic models.  The dense spatial sampling of the Mars Orbiter Laser Altimeter (MOLA) dataset makes it useful as a source of horizontal control as well:  features in images can easily be recognized in the altimetry and can be assigned coordinates with such small uncertainties that they function effectively as ground control points in the photogrammetric bundle-block adjustment.  Such MOLA-derived ground points will be used to further improve the Viking Orbiter based control network and MDIM late in 2001 and will be incorporated into a subsequent network and mosaic based on global stereo imagery from MOC.