Rosetta PDS, Images and other products made from archived data |
Rosetta PDS, Images and other products made from archived data |
Dec 14 2015, 10:48 PM
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
As we have now access to archived OSIRIS images and data from other instruments, I think that it's good idea to start up special topic for that.
Here are few results from the newly published data: Hi-Res crosseye stereo color image of Imhotep regio at resolution 0.5 m/pix. Anaglyph version: Global color image at 2.2 m/pix: -------------------- |
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Dec 15 2015, 12:14 AM
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
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Dec 17 2015, 08:05 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I guess we can't say too much about the colour given that the hue is pretty much uncorrelated with the topography and looks mostly like noise: The strange noise-like aspect of the color variations has been bugging me ever since I saw the first color image released. In this dataset, I noticed some images don't appear to suffer from it, some do. Turns out it can vary even across a single image. Whole sections of roughly 500x500 pixel size can be affected. When you boost brightness, it shows a tell-tale sign of lossy compression. Turns out wavelet-like compression can be used by the flight software, but the compression params have to be among the weirdest I've seen. They preserve higher frequency detail while the low frequency component of around 16x16 blocks can be clobbered and this is what causes the mottling noticeable in color composites. Example attached. This is most noticeable in global images like this, perhaps they fixed it in subsequent observations. Related to this, most of the subsequent, really high res NAC green frames seem to be severely more compressed than red and blue counterparts, but at least the mottling seems to be gone. -------------------- |
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