shape from shade, so i do not take over Bjorn's |
shape from shade, so i do not take over Bjorn's |
Apr 7 2010, 04:03 AM
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#1
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
So that i do not take over his nice thread i figured i would start a new one
I am just figuring it out so bear with me Rhea This is a example - very early example http://www.shatters.net/forum/viewtopic.php?f=5&t=15847 one that i am going to redo . the program i am using "Cyclops" has a few bugs Enceladus this is a good example a bit better than the above the close ups are a 8k level 3 VT with and without a texture over it then a 4k level2 vt unfortunately i still have to figure out a bug .I need to run a highpass on it ( the 32 bit isis dem ) Cyclops exports to a 3d *.ply this is easy to export to a isis cub and i get this ( this happens when i combine 16 smaller images into one big one ) and this example is at 1/2 size Just a bit of a bug !!! |
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Oct 23 2021, 07:00 PM
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#2
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Solar System Cartographer Group: Members Posts: 10229 Joined: 5-April 05 From: Canada Member No.: 227 |
Schenk, P., McKinnon, W.B., Moore, J. and Nimmo, F., 2021, March. The Topography of Ganymede (and Callisto): Geology, Global Characteristics, and Future Exploration. In Lunar and Planetary Science Conference (No. 2548, p. 2228).
This is a recent discussion of topography on Ganymede and Callisto which shows how very limited the stereo coverage is. Here's a link: https://www.hou.usra.edu/meetings/lpsc2021/pdf/2228.pdf Nobody knows more about icy satellite topography than these authors. 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 PDF: 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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Oct 23 2021, 10:48 PM
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#3
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Member Group: Members Posts: 127 Joined: 15-April 21 Member No.: 9009 |
Schenk, P., McKinnon, W.B., Moore, J. and Nimmo, F., 2021, March. The Topography of Ganymede (and Callisto): Geology, Global Characteristics, and Future Exploration. In Lunar and Planetary Science Conference (No. 2548, p. 2228). This is a recent discussion of topography on Ganymede and Callisto which shows how very limited the stereo coverage is. Here's a link: https://www.hou.usra.edu/meetings/lpsc2021/pdf/2228.pdf Nobody knows more about icy satellite topography than these authors. Phil yeah, i have seen that before, i even tried finding the PC DEM coverage in other papers to make a Ganymede DEM map from the data, but i failed miserably |
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Oct 23 2021, 11:26 PM
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#4
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
I even tried finding the PC DEM coverage in other papers to make a Ganymede DEM map from the data, but i failed miserably The paper itself makes this clear. They state that less than 20% of the surface has usable data. Those oddly-shaped pieces do not overlap, so it is impossible to calibrate their relative altitudes together. The paper is full of interesting comments about Ganymede's and Callisto's global topography around the overarching fact that our knowledge is spotty for now. |
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Oct 24 2021, 07:00 PM
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#5
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Here's the full text of a paper explaining the methodology necessary to use shape-from-shading to produce a local DEM for lunar surfaces. This is 2018 work even though we've had good images of half of the Moon for many decades. It depends upon generating a model of reflectance functions for the lunar surface, estimating the variations in local intrinsic albedo, accounting for said albedo, and the fact that estimates may be checked against data derivable from other sources.
https://www.sciencedirect.com/science/artic...924271617303878 Note, this is much, much more complicated than running a Photoshop filter on an image. It'll be a major research project to attempt the same for Ganymede, etc. And, simply put, a successful mapping campaign from JUICE would certainly enable the production of a detailed, global topographic map of Ganymede and make obsolete anything done prior to that, and we'll see such a map around 2035 if the mission is fully successful. Europa Clipper will similarly, but perhaps not quite so well, give us a global topographic map of Europa. As Van says here, of "medium-resolution": http://futureplanets.blogspot.com/2013/05/...per-update.html JUICE and Europa Clipper will make a total of 21 flybys of Callisto, which would certainly upgrade our coverage of that world far beyond the current status, but almost certainly wouldn't be sufficient to produce a seamless global topographic map. It should give us detailed local topography in many places and perhaps detect any global deviations from sphericity, although Callisto might be a good bet for being one of the most nearly spherical bodies in the solar system. About 15 years from now, we'll hopefully have Ganymede's topography characterized about as well as we now have for terrestrial planets, the maps for Mercury and Venusian will be better than now, we'll have a global topographic map of Europa that's good but not as detailed as we have for the terrestrial planets. Io and Callisto will remain partial and spotty. |
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