CARTOGRAPHIC AND TOPOGRAPHIC MAPPING OF THE ICY SATELLITES OF 
THE OUTER SOLAR SYSTEM 
P.M. Schenk 
Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston Texas USA 77058 - 
schenk@lpi.usra.edu 
Commission IV, WG IV/7 
KEY WORDS: Extra-terrestrial, Photogrammetry, Cartography, Geology, Mapping 
ABSTRACT: 
Cartographic and topographic mapping of the major satellites of the Outer Solar System has been in progress since the late 1980’s, 
beginning with Voyager image data, and incorporating Galileo and recently Cassini imaging data as released to the public. Global 
image mosaics, based on cartographic control nets, have been produced for all these satellites. In addition, digital topographic maps 
have been produced for restricted areas on the Galilean, Uranian satellites, and Triton. Global topographic maps as well as limited 
high resolution topographic samples have been produced for the Saturnian satellites. These data have been used to investigate the 
properties of the icy outer layers (esp. Europa and Io), discrimination between competing hypotheses of geologic origins (on Triton, 
Ganymede, Europa, and Enceladus for example), and in some cases the thermal histories of these bodies (esp. Ganymede and Dione). 
These data are available on request for use in mapping and modelling of geologic and geophysical processes. 
1. INTRODUCTION 
1.1 Purpose 
Since 1979, Voyager, Galileo, and now Cassini have unveiled 
over a dozen new worlds in the outer Solar System. With the 
exception of Io (its soulful dioxide coatings notwithstanding) 
these moons of the outer planets are almost all dominated by 
icy mantles tens to hundreds of kilometres thick. Although 
subject to similar geologic forces as on Earth or the Moon, their 
icy composition leads to geologic landforms that are both 
familiar and alien. Key to understanding these landforms and 
the geologic processes and stresses responsible for them are 
accurate cartographic and topographic tools and data sets. 
Several groups have been working these problems, and here I 
report on mapping products for these objects generated by our 
group at the Lunar and Planetary Institute over the past decade. 
1.1.1 Cartographic Mapping: Production of reliable global 
maps is key to testing models for tectonic feature formation and 
global heating. Using USGS ISIS software, global maps of 
nearly every major satellite (those larger than -100 km radius) 
have been produced. Control of images to produce global 
mosaics has been an ongoing task but is critical to mapping 
reliability. Starting with satellite radii from Thomas et al., 
(2007) and other sources, we have produced independent 
control networks for all icy satellites. Mapping of Saturnian 
satellites is ongoing as new data are released to the PDS, but 
other satellite mapping has been completed. 
1.1.2 Topographic Mapping: Two topographic techniques 
are applied, either separately or in combination. 
Stereogrammetry has been the workhorse for these bodies, 
especially in the absence of altimetry instruments. 
Stereogrammetry provides reliable height information at all 
wavelengths but its dependent on scene content. Large areas of 
smooth nearly featureless volcanic plains on Io are not 
mappable using this technique, for example. Most icy satellites 
have high surface contrast at small wavelengths and stereo 
matching provides excellent results. However, stereo coverage 
can be poor in many areas, especially at Jupiter, and the stereo 
matcher degrades digital elevation model (DEM) resolution 
relative to the original images by factors of 5 or more. Shape- 
from-shading (photoclinometry, PC) has greatly expanded areal 
coverage of topographic mapping and produces DEMs with 
high resolution identical to the original images, but is not as 
stable at wavelengths longer than 50-100 pixels in the image 
plane. In many instances, however, stereo and PC overlap, 
allowing the former to control the uncertainties of the later. 
This merged stereo-PC technique has been especially profitable 
for Europa and the Saturnian satellites. 
2. JOVIAN.GALILEAN/MEDICIAN SATELLITES 
2.1 Cartography 
Unlike the new systematic Cassini global mapping mosaics for 
the icy satellites of Saturn, Galileo’s crippled communications 
has a near-catastrophic impact on cartography including both 
global and especially topographic mapping. Global mapping of 
the Galilean satellites is possible at 1-kilometer scales (not 200 
meters as should have been), and these maps are now complete 
(Figure 1), based on our independent cartographic network. 
Mapping at 200-300 meters was also acquired by Galileo, but 
only for 5 to 20% of these surfaces. These maps combine the 
restricted Galileo and more global (but lower resolution) 
Voyager mosaics, and include near-global coverage in 3 colours. 
In addition, all Galileo high-resolution (5 to 500 m/pixel) 
images of the 4 satellites have now been coregistered to the 
global control network (e.g., Figure 2), integrating them into 
our global digital map bases. This work (as on all the satellites) 
has been critical for accurate topographic mapping and DEM 
production. All of these products will be published together in 
2008. 
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