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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
On a global scale, we confirm the depressed topography of the 
south polar terrains, but have also discovered large scale 
“dimples” in the topography of Enceladus (Schenk and 
McKinnon, 2008). These include at least two broad depressions 
roughly 100 km across and 1 to 1.5 km deep. These are located 
near the equator and at roughly 40°N latitude. They are located 
within older cratered terrains or on the contact between cratered 
plains and very young ridged plains, indicating that there is no 
correlation with geology. They could represent isostatic 
warping of the surface over irregularities in the rocky core or 
over downwelling/upwelling plumes in the icy mantle, or more 
likely isostatic depressions over mass anomalies. 
4. URANIAN & NEPTUNIAN SATELLITE 
4.2 Uranian Satellites 
Voyager 2 data from 1986, obtained during southern summer, 
provided views of only 25-45% of the surface, almost all at 
southern latitudes (Figure 7). Excellent stereo imaging was 
obtained for Miranda and Ariel (Figure 8) and good stereo for 
parts of Titania. These data are locally supplemented by 
terminator photoclinometry. Oberon, Umbriel and Puck were 
too far away for anything other than reconnaissance images. 
DEMs of these satellites are largely unpublished but early 
analyses documented the depths of craters on the three mapped 
satellites (Schenk, 1991), and showed that some large craters on 
Ariel are also viscously relaxed or flooded by lavas (Schenk 
and McKinnon, 1998). 
Figure 7. Global map of Ariel. Map is in simple cylindrical 
projection. Note northern hemisphere obscured by darkness, 
and use of Uranus-shine images north of the equator. Dark 
swath extending northward may be extension of volcanic plains. 
4.3 Triton 
Geologically useful stereo DEMs of Triton based on Voyager 
images cover only a modest fraction of the surface (<10%). 
Although these data have poor resolving power (50-200 m 
vertical), they were sufficient to demonstrate that the centres of 
cantaloupe terrain ovoids are depressed a few hundred meters 
(Schenk and Jackson, 1993). The poor performance of these 
data products is due mainly to the small stereo angles (imposed 
by the encounter geometry and distance), and by the inherently 
low topography of the surface. Few features on the surface 
have amplitudes greater than 250 m. Instead we rely on 
photoclinometry, which covers a 10-15° swath parallel to the 
Voyager terminator (Figure 9). These data have resolutions of 
0.7 to 1.5 km and much higher vertical fidelity than stereo 
products. 
Figure 8. Topographic map of Ariel. Orthographic projection 
of base map has been colour-coded to show topography (red 
high, blue low). Topographic range displayed in colour bar is 
-5 kilometres. 
Figure 9. Topographic map of equatorial regions of Triton. 
Orthographic mosiac (north to right) has been colour-coded to 
show topography (red high, blue low). Total dynamic range is 
~0.5 km. Data derived form photoclinometry only. Individual 
geologic features are well represented, but long-wavelength 
topography (likely of very low amplitude) is not regarded as 
reliable. Large amplitude features along the left edge of the 
DEM may be photoclinometric artefacts. 
5. CONCLUSIONS 
Cartographic and topographic mapping of the icy satellites of 
the Outer Solar System is an ongoing task, especially for the 
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