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: 10185 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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Dec 7 2014, 06:57 PM
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#2
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Member Group: Members Posts: 241 Joined: 22-August 05 From: Stockholm Sweden Member No.: 468 |
I'm proud to announce the release my latest Shape Model!
Download on my blog: http://mattias.malmer.nu/2014/12/new-shapemodel/ |
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Dec 9 2014, 08:07 AM
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#3
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Junior Member Group: Members Posts: 81 Joined: 10-August 12 From: Kingston, Ontario, Canada Member No.: 6534 |
...my latest Shape Model! Many thanks, this is great! I've now been able to align the sight lines from Rosetta to Philae with those from Philae to approximated locations on your model (after registering an OSIRIS image from Sep. 14 using MeshLab). The resulting solution (basically bundle adjustment) rotated your model about 10 deg in roll and pitch and about 165 deg in yaw (lining it up closer to the ESA .obj file), and nicely only applied a 3.8% increase in scale. The centroid also shifted about 0.5 km, mostly in the z-axis. Attached are some plots of the results. The first figure shows Philae's trajectory in blue, with sight lines coming from Rosetta in pink for each time the lander was spotted in the OSIRIS frames (blue circles marking the locations in Philae's trajectory, red X's marking the approximated locations in the registered image). The green lines are sight lines to the post-touchdown positions (one from the OSIRIS image series, the other from the NAVCAM image) and the yellow line is the sun vector emanating from the location of the shadow in the NAVCAM image. The second figure is an overall view with Rosetta and Philae trajectories (red and blue, respectively) included. You can also see Rosetta's position and orientation at the time the registered image was taken (Sep. 14, 17:48) and the camera location used for image registration (a separate process but could be linked to aid in the solution). The third plot shows a "top-down" view to make comparison with the OSIRIS touchdown images easier. |
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Dec 9 2014, 04:01 PM
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#4
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Senior Member Group: Members Posts: 4251 Joined: 17-January 05 Member No.: 152 |
Attached are some plots of the results. Can you predict the positions of the lander shadow on the ground, for the three pre- and one post-first-bounce OSIRIS images? I'm curious if they're outside the released frames, since there's no sign of shadows in those images. Of course the released OSIRIS is a composite and it may not be clear exactly how far each individual frame extends. But based on the lander's height, I might have guessed the shadow would be visible in the post-bounce part of the image (or maybe just off it to the right). |
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