Map Features Overlays on a Cylindrical Projection |
Map Features Overlays on a Cylindrical Projection |
Jan 28 2012, 07:25 PM
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Senior Member Group: Members Posts: 1656 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Greetings,
Thought I'd mention I'm starting a mini-project to make map feature overlays for planets and satellites. These are set up on a cylindrical projection so they can be displayed with Science On A Sphere, Celestia, and the like. The key is that text for feature names has to be "pre-distorted" so it looks correct when viewed on a sphere. This is especially important at high latitudes. The overlays are for now in the form of transparent PNG images. So far I've started with Mars and Enceladus. The programming language is IDL, and the lat/lon info for the feature names is from the USGS Map-A-Planet Gazeteer. I'll try to post some results once they are a little better. Enceladus is a special case, since the map I had put together is in planetocentric coordinates, and the feature lat/lons are in planetographic. So a conversion of one or the other would need to be done. Steve -------------------- Steve [ my home page and planetary maps page ]
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Feb 4 2012, 03:45 AM
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Solar System Cartographer Group: Members Posts: 10197 Joined: 5-April 05 From: Canada Member No.: 227 |
Don't get too hung up on the question of having 0 or 180 in the middle. There is no right or wrong. Sometimes you need to fit a standard required by software, maybe, but think of Earth. Put 0 in the middle, 180 at the edges, and you are splitting the Pacific Ocean in two. If you want to show the Pacific whole, put 180 in the middle. Every application has its own needs. Just do what works.
Doug's PDS quote has nothing to do with the central longitude of a map. It is just saying you can use negative longitudes (up to -180) in those specified cases, but elsewhere longitudes are defined just as 0 to 360. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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