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 Post subject: Old Phobos in New Color
PostPosted: Mon, 26-05-08, 17:27 GMT 
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Hi all,

after those spectacular new color images of Phobos by HIRISE,

http://hirise.lpl.arizona.edu/phobos.php

a great and worthwhile task is of course to reproject those images via ISIS3 and eventually achieve a GREAT 4k color texture of phobos. While this may be boiling slowly in someone's imaging "cuisine" (ahem ;-) ), here is a quick modification of Celestia's present phobos texture that all of you can easily do yourselves. It is a direct application of the "mini-tutorial" I gave yesterday about GIMP-coloration by means of a color template.

http://forum.celestialmatters.org/viewt ... 4&start=14

So let's just use the present (medres) phobos texture and load it together with a reduced version of the new color imaging

http://hirise.lpl.arizona.edu/images/20 ... 10_IRB.jpg

which will serve as a color template. But please, reduce the template to 1k width beforehand. Since the present medres texture is pretty "rough" and lacking many subtle tones of gray, you cannot possibly map all those delicate shades from the new hires color photo. If you have questions, about how I got the white color around the great Stickney impact crater, let me know. I will write another mini-mini tutorial about this, in case of problems ;-)

Here is my result along with a comparison with the new color imaging by HIRISE at the bottom:

Image

Cheers,
Fridger


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 Post subject:
PostPosted: Tue, 27-05-08, 2:16 GMT 
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t00fri wrote:
a great and worthwhile task is of course to reproject those images via ISIS3
I tried this a couple of months ago and found that ISIS needs a "Shape Model" to project this image. Also there was some kind of error in the geo data in one of the ccd "channels.
http://isis.astrogeology.usgs.gov/IsisS ... =5857#5857
This is also false color. IRB. When you look at the wavelengths that the HiRise camera uses they are way out of the normal human site range.
cartrite


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 Post subject:
PostPosted: Tue, 27-05-08, 9:06 GMT 
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cartrite wrote:
t00fri wrote:
a great and worthwhile task is of course to reproject those images via ISIS3
I tried this a couple of months ago and found that ISIS needs a "Shape Model" to project this image. Also there was some kind of error in the geo data in one of the ccd "channels.
http://isis.astrogeology.usgs.gov/IsisS ... =5857#5857
This is also false color. IRB. When you look at the wavelengths that the HiRise camera uses they are way out of the normal human site range.
cartrite


As to the color, you are of course right. IRB is not exactly what present day Celestia without "multi-wavelength" window can make use of ;-) . A comparison of the HIRISE color images with the CRISM ones from 2007
http://crism.jhuapl.edu/gallery/feature ... age_id=102
is also interesting. They state clearly that both Phobos and Deimos are largely of redish color.

So, the above image may just be considered as an exercise in GIMP coloration...

As to a simple cylindrical projection of these new hires data, I remember we communicated about your respective ISIS3 problems, when you tried it all within ISIS3. My approach is more conventional for now. I am mainly using my old reprojection method based on Matthew Arcus' MMPS software and adjust the result to fit onto the enlarged existing texture. That method I have used for years ;-)

Fridger


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 Post subject:
PostPosted: Tue, 27-05-08, 21:45 GMT 
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Are there any colour images which contain both Phobos and Mars with which to make a comparison?


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 Post subject:
PostPosted: Wed, 28-05-08, 0:17 GMT 
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Good point Andrew,

certainly there are plenty of Mars shots by HIRISE with the same IRB filters:

E.g. 2007:
http://images.google.com/imgres?imgurl= ... n%26sa%3DG

Fridger


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 Post subject:
PostPosted: Sun, 31-08-08, 21:41 GMT 
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I am finally able to project these Phobos images. Not entirely sure that I got it exactly right yet. I was able to come up with a shape file of Phobos by importing an ascii file I found that has a radii every 2 degrees.
http://www.psi.edu/pds/asteroid/EAR_A_5 ... V2_0/data/
Its a little file and I think that I probably need a bigger one but this is the only one I found. It makes a cute little model too.
Here are a couple of jpgsImage

Image

Image

The second one is the one I used. I changed it to Positive East.

Anyhow here are the results of the HiRise maps.
PSP_007769_9010
Image

Image

PSP_007769_9015

Image

The originals are at 6 meters per pixel.

Looks like more images are needed before it is useful no matter how it is projected.
cartrite


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 Post subject:
PostPosted: Mon, 01-09-08, 0:28 GMT 
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This is what this map looks like with a "positive west ?" shape file. I'm not quite sure what is what. The ascii file lists radii in km from 0 to 360, starting at -90 and goes to 90.
After I saw the image from this file in qview, at fist glance it looked alright but after I compared it to the phobos texture in Celestia, everything was backwards.
So I assumed that the ascii was positive west and I created a map file that says it was positive east. Anyhow that brings up a question.
Is the Phobos map in Celestia correct?
When I use the data as is and call it positive east, a mirror image of the Phobos texture in Celestia, I get a map that looks like this.

Image

If anything, this shows how a shape file influences a map projection in ISIS3.
cartrite


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 Post subject:
PostPosted: Mon, 01-09-08, 7:40 GMT 
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This model seems to be better than the Celestia original, no? Would you post the model to have a look?

Now, if I understand, all the mapping process depends in that case of the model used? The resulting map will be ok for a specific model and could be wrong on another or the difference would not being perceptible?

In such exercise, how one delimit the zone that can be used for the map? (here seems only a little central part is useful, no?)


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 Post subject:
PostPosted: Mon, 01-09-08, 9:23 GMT 
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You really think this looks better than the one in Celestia?
I didn't run the model in Celestia yet, it is still in Blender format and has no u/v coordinates. I can try to map them in a couple days.

I was just curious about what it would look like because it only had 180x90 coordinates. The little height maps above are the actual size. If you look at the upper right of the Blender screen shot, you'll also see that it has 16k faces. Probably the smallest I ever did.

Quote:
Now, if I understand, all the mapping process depends in that case of the model used? The resulting map will be ok for a specific model and could be wrong on another or the difference would not being perceptible?

In such exercise, how one delimit the zone that can be used for the map? (here seems only a little central part is useful, no?)

These shape files to do the mapping in ISIS3 are supplied by the ISIS installation and yes, they are very complicated to get right. The map projection programs depend on shape files. But there was no shape file for Phobos in ISIS so that is why I'm trying to make one.

Yes, For a complicated ellipsoid like Phobos, only image portions that are directly overhead are going to be usable. Trying to map a crater that is viewed from the side is at best a guess even if it is placed in the right position.

I'll probably crop the usable portions and map them. Then I'll try to oversample the 1k phobos.jpg from Celestia to 4k or so and and the usable portions. But I want to make sure that the mapping is being done correctly first.

cartrite


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 Post subject:
PostPosted: Mon, 01-09-08, 9:42 GMT 
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cartrite wrote:
You really think this looks better than the one in Celestia?...


Seems to be smother than the Celestia default, no? Or perhaps I don't have the correct model?? The one I have is around 6k poly...


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 Post subject:
PostPosted: Mon, 01-09-08, 10:08 GMT 
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Actually, they look almost the same. I think they probably use the same source data? I'm not sure what was used to create the Phobos model in Celestia.

Image

I was unable to find what coordinate system was used in the ascii file. Positive east or positive west? Every 2 lat/lon coordinates has a radius. They are in order from 0 to 360 on every line. A line will read 8.0000,134.0000,12.56950. The 12.56950 is the radius at 8 degrees latitude 134 degrees longitude. But is it east or west? Those 2 points are km apart.

All I needed to create the model was the list of radii sorted in the proper order. Then I instruct ISIS that the ascii file I'm importing is 180 records long (samples) and 90 lines. I just need to find out how that data was sorted. 0 deg latitude 2 deg longitude positive east is the same as 0 deg lat 358 degree longitude positive west. They have 2 different radii in the ascii file.

cartrite


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 Post subject:
PostPosted: Mon, 01-09-08, 12:08 GMT 
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cartrite wrote:
Actually, they look almost the same. I think they probably use the same source data? I'm not sure what was used to create the Phobos model in Celestia.


Yes they looks identical.


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 Post subject: re
PostPosted: Mon, 06-07-09, 6:49 GMT 
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this is the shape file i am using
It is PositiveEast -- for celestia 0 long is in the center
Image
but isis is throughing an error

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 Post subject: re
PostPosted: Thu, 30-07-09, 2:16 GMT 
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just an update .I still have not looked into the error i was getting .
however i have been converting the Phobos.tab file ( the 0,2,4,6,8,... deg) from Phil Stooke
a few shots in celestia and the last is blender
Image Image Image Image

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 Post subject:
PostPosted: Thu, 30-07-09, 23:20 GMT 
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These polar pinches are still annoying... :(
Still quite a nice update! :D


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