Reprocessing Historical Images, Looking for REALLY big challenges? |
Reprocessing Historical Images, Looking for REALLY big challenges? |
Apr 21 2005, 11:26 PM
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Member Group: Members Posts: 123 Joined: 21-February 05 Member No.: 175 |
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May 30 2005, 09:50 PM
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Member Group: Members Posts: 378 Joined: 21-April 05 From: Portugal Member No.: 347 |
Interesting images ! Very nice!
But those hills... are there really hills in the original images? Perhaps just some rock layers on the horizon. Without geometrically corrected images it's difficult to judge. I tried everything in my power to correct the Venera images with no results... I even projectes the images into the inside of a sphere in Celestia and used the mouse to look around. It corrected some distortions, but not all! -------------------- _______________________
www.astrosurf.com/nunes |
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May 30 2005, 10:31 PM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
QUOTE (4th rock from the sun @ May 30 2005, 02:50 PM) Interesting images ! Very nice! But those hills... are there really hills in the original images? Perhaps just some rock layers on the horizon. Without geometrically corrected images it's difficult to judge. It is difficult to distinguish the scales, but there are almost certainly some real hills somewhere in these images, esp. Venera 13. The camera is about 2m high, so no mere bumps in the foreground can appear so far away. The Magellan data shows some of these landing sites to be in rather rough areas, so hills should be no surprise. QUOTE I tried everything in my power to correct the Venera images with no results... I even projectes the images into the inside of a sphere in Celestia and used the mouse to look around. It corrected some distortions, but not all! I have tried many things, as well, and eventually got some decent results in more than one way. For the base images in this set, I used the spherical distortion tool in Photoshop, but you have to get the parameters right. I basically placed the original rectangular strip of each Venera image near the top of a much larger square, then applied the spherical distortion tool. This did not remove all distortion (the reasons why are below), but for my chop-and-paste purposes, that hardly mattered. Originally, I attempted a math-first approach using the engineering specs of the Veneras, but this didn't work because none of the landers rested horizontally, and apparently some of the edges of the images have been cropped away, so the image geometry doesn't match the engineering specs. A very laborious hand-adjustment of each image is also a way to go, and I attempted that at one point, but even when you're done, you get bowl-shaped images, and that's when I realized that I wanted to re-arrange the imagery [realistically] instead of performing a simple reprojection, and then the demands for accuracy are a bit less when "up" doesn't need to be perfect up. I should add that my cloning almost always maintains the approximate correct distance-to-horizon of each parcel of image. These really should represent the way a venusian landscape *could* look, even if the particular rocks at these landing sites happen to be arrayed differently. Sooner or later, we'll get a Venusian "Huygens", but without the data rate constraints and descent+surface imaging will make all of our eyes happy. Until then, manipulation of Venera imagery is all we have. |
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