It is often difficult to judge the scale of a planet or moon. This add-on creates a set of alternate surface textures which superimpose maps of familiar terrestrial locations on various solar system objects (mapped planets or moons with radii > 100km).
Unzip this file into your extras folder, and it will create a directory called ComparisonMaps. This contains the ssc file and texture folder necessary to generate the alternative textures. Right-click on a planet or moon, and an alternative surface called "Map Overlay" will be offered. When selected, this superimposes an overlay map on the default Celestia texture. All the overlay textures are named "Map Overlay": once this option is activated, the comparison maps are superimposed on all major solar-system bodies.
For the convenience of those writing educational scripts, each comparison map is centred on a location called "Map", which is of negligible size so that it will not be labelled during normal viewing. These locations are defined in a file called comparisonmap_locs.ssc. Because of the difference in curvature between the Earth's surface and the surface of other planets and moons, the map scales are by no means precise - they should be used as no more than a visual cue to approximate size.
The following maps are used:
Apologies to those living outside the U.S.A.! If enough interest is shown, I plan to produce parallel map sets using locations in Europe and Australasia.
Grant Hutchison, March 2004
This Web page is maintained by Selden Ball
at Wilson Lab.
Please send any comments or corrections to firstname.lastname@example.org