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Enceladus PDS image products
Bjorn Jonsson
post Jul 22 2010, 03:22 PM
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Following discussions in the Image Processing Techniques subforum (see in particular this thread but also this one) I have now managed to create DEMs of acceptable quality of Enceladus using shape from shading and extensive post processing (mainly destriping). I now have a DEM mosaicked together from 5 images obtained during Cassini's first flyby of Enceladus in 2005. This will eventually become a global 23040x11520 pixel DEM but finishing it is going to be a lot of work (I will probably be using 50-100 images or more). Not all of Enceladus has been imaged at this resolution but there are many high resolution patches and I want a DEM big enough for these.

This 5 image DEM was big enough for me to really want to see what an Enceladus DEM animation would look like. So here we go:

Attached File  enceladus_sfs_umsf.avi ( 7.74MB ) Number of downloads: 532


The field of view is 50 degrees. Most of the animation is at an altitude of 25-30 km. This is similar to Cassini's altitide during the closest flybys and the speed is not far from Cassini's speed either. However, the animation starts and ends at higher altitudes and we also swoop down to an altitude of ~10 km where the resolution of the DEM is highest.

This is the Cassini image I used for the highest resolution part of the DEM:

Attached Image


And a single frame from the animation showing a part of this terrain:

Attached Image


The DEM should be fairly accurate - in particular the animation should give a very good general idea of what Enceladus looks like even though some details are inaccurate. Also a higher resolution DEM is really needed for these low altitudes - the surface should look less smooth than it does here. Most of the striping is real though as there are lots of parallel ridges and grooves on Enceladus. There may be some spurious stripes but these are very subtle - the obvious ones are real.

I'll do a new animation once I have a significantly bigger DEM. It will probably have better optimized illumination. Shadows are really needed in the first half of this one because I optimized the illumination for the highest resolution part of the DEM. We fly over that part of the DEM at roughly 00:30.

EDIT: To play the animation you need to have an H.264 codec installed (if you are using Windows you can find one here for example).
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charborob
post Jul 22 2010, 03:47 PM
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I must be missing something in my version of Quicktime because I can't play your .avi file. I'll try to fix that. In the meantime, can you tell me how much vertical exaggeration you have in your rendering?
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Bjorn Jonsson
post Jul 22 2010, 03:55 PM
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I forgot to mention that to play the animation you need to have an H.264 codec installed (if you are using Windows you can find one here for example).

There is no vertical exaggeration but the true vertical range was rather difficult to estimate accurately. I ended up repeatedly adjusting it until the rendered images approximately matched Cassini's images when using identical illumination and viewing geometry.
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Floyd
post Jul 22 2010, 06:16 PM
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Very nice! And thanks for the directions to the codec. When I first just tried to open it, my Real player tried but fiailed. When I saved it and opened with Windows Media player all went well.


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lyford
post Jul 23 2010, 12:46 AM
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Beautiful - thank you!


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nprev
post Jul 23 2010, 01:59 AM
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blink.gif ...outstanding, Bjorn, thank you!!!


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Ian R
post Jul 23 2010, 03:43 AM
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Very well done!


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JohnVV
post Jul 23 2010, 09:41 AM
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very nice

it is time consuming isn't it

by the way what program are you using to make the vid .
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Bjorn Jonsson
post Jul 23 2010, 07:18 PM
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Yes, finishing the DEM is time consuming - it's going to be a lot of work (I'm not even sure I'll finish it this year).

The individual frames are rendered using software written by myself and then assembled into an AVI file using VideoMach.
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Bjorn Jonsson
post Apr 19 2011, 02:10 AM
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After seeing machi's anaglyphs of Titania I decided to see what an anaglyph of my Enceladus DEM looked like - actually my first ever anaglyph. This first experiment turned out way better than I expected so here it is:

Attached Image


Now I really want to do an anaglyph animation of Enceladus.
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machi
post Apr 19 2011, 11:27 AM
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Very nice!
I'm glad, that my work is inspirational. smile.gif

"Now I really want to do an anaglyph animation of Enceladus."
That would be really wonderful and I think, it would be first such Enceladus' animation.


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Phil Stooke
post Apr 19 2011, 03:14 PM
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Right... approaching the south pole with the plumes rising above the horizon, and then weaving between the plumes... cool!

Phil


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Bjorn Jonsson
post Apr 20 2011, 11:06 AM
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QUOTE (Phil Stooke @ Apr 19 2011, 03:14 PM) *
Right... approaching the south pole with the plumes rising above the horizon, and then weaving between the plumes... cool!

This would be cool once I have finished a DEM of the south polar region (I'm working on a global DEM of Enceladus). The DEM I currently have is near the equator only.

And here we go, an anaglyph animation of a Enceladus:

Attached File  encel_anaglyph_xvid.avi ( 2.16MB ) Number of downloads: 245


This is the same general area as in the earlier animation but the flight path is different and shorter (the altitude is constant at ~25 km). Needless to say you'll need red-blue glasses to view this properly.
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machi
post Apr 20 2011, 12:29 PM
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Superb work!

Can you make this animation in reverse direction (opposite view, from flat terrain to mountainous terrain) and approx 2× slower (it's so nice and so quick smile.gif )?


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Bjorn Jonsson
post Jun 28 2011, 08:46 PM
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As I have mentioned, I'm working on a DEM of Enceladus using images from the PDS. Using these images can result in considerably higher quality than using the raw JPGs. This is a by-product of the DEM processing, a 12 frame mosaic of images obtained during Cassini's first close flyby of Enceladus back in February 2005:

Attached Image


North is up. This is the first Cassini image product where I used ISIS to a significant extent - for the processing I used various software including ISIS, Photoshop and software written by myself. I used ISIS mainly for correcting the camera pointing angles (this turned out to be suprisingly easy to do once I got past some initial problems using ISIS). The more accurate pointing makes it easier and faster to get the images properly aligned and also yields more accurate results. Soon I should also have a DEM of most of this terrain (the main exceptions are terrain near the terminator and near the limb).

And here is a wide angle context image:

Attached Image


I may post more image or mosaics here later. Needless to say, anyone is welcome to post Enceladus-related PDS work here.
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