3D shape, cartography, and geoid of Comet 67P C-G |
3D shape, cartography, and geoid of Comet 67P C-G |
Aug 6 2014, 02:11 PM
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#1
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Solar System Cartographer Group: Members Posts: 10174 Joined: 5-April 05 From: Canada Member No.: 227 |
Explorer 1 said:
"A 2D map of C-G seems like a tough order; the projection math alone..." Don't worry! If you can put a grid on the surface (as we have seen already), you can warp that grid into any map projection you like. Mapping will be no huge problem - in fact I expect they have a rough one already (I've been playing with one myself). 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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Aug 25 2014, 10:42 AM
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#2
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
I have seen members here mention generating synthetic "in-between" frames from two images, so this is a callout for someone to hopefully generate a bunch of frames between the two fantastic OSIRIS images that made up that 3D view: http://blogs.esa.int/rosetta/2014/08/14/comet-67pc-g-in-3d/ The generated frames could be used to create a more "comfortable" anaglyph, or even an animation of the comet's rotation. It's possible (and Gerald already did this) but it's complicated by the shape of 67P and it's very time consuming job especially in case of rotation animation (which is possible thanks to the NavCam images). My guess is at least one hundred control points for every pair of images. For whole animation (one revolution) it's 1300-1500 control points. I'm playing around making a highresolution 3D representation of Comet 67P/Churyumov-Gerasimenko using a hybrid stereo correlation/shape from shading approach... Take a look: http://mattias.malmer.nu/wp-content/upload...683D8388A36.mov It looks very impressive! It reminds me some works from the former(?) UMSF member who did 3D images from HiRISE cameras by shape-from-shading method. -------------------- |
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Aug 25 2014, 12:08 PM
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#3
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
... it's very time consuming job ... My guess is at least one hundred control points for every pair of images... By automated matching of 256x256 = 65536 (overlapping) small tiles, and storing the respective displacements, I've tried to get this somehow managed. But areas with few features, e.g. large shadows or very smooth patches, are hard to match, and result in very noisy parts, despite noise filtering. Some features aren't visible in both images, so again hard to match. Here a visualization of such a displacement map: The displacement map can then be used to generate a radius map (kind of a depth map), provided some telemetry data are known or estimated: From this, a 3d-mesh could be generated. (But the quality of the above map isn't too convincing.) I've used the displacement map to generate the interpolated frames. (Credit for the underlying images, used to generate the above maps: ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA) |
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