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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: 689

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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Bjorn Jonsson
post Mar 4 2012, 08:14 PM
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Posts: 1915
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From: Near fire and ice
Member No.: 38

My latest animation:

Flight over Enceladus

This is an almost 7 minute animation featuring a digital elevation model (DEM) covering roughly 50 percent of Enceladus' surface. It is the most complex and by far the biggest animation I have ever done. The DEM is created from 55 of the images Cassini obtained during its three close flybys of Enceladus back in 2005. The flight path, viewing and illumination geometry is carefully selected to completely hide the fact that the DEM is not global. The DEM's resolution varies from ~70 to ~350 m/pixel. The field of view is 50 degrees.

The DEM is created using a very simple shape from shading algorithm (SFS) followed by 'destriping' and extensive post processing. A significant amount of the processing is based on (or some processing ideas were indirectly triggered by) various tips posted in several threads here (in particular, some of JohnVV's posts were helpful). All of this processing was done using a mix of ISIS 3, Photoshop and software written by myself. The individual frames were rendered using a renderer written by myself. The first frames were rendered in early December but due to the size of the DEM and this animation project several things have changed since then. The most significant change is that I finally built a 64 bit version of the renderer in early January (the DEM is too big to be easily manageable at close range using the old 32 bit version).

Since the DEM is created using SFS, vertical exaggeration is variable across the DEM. I tried to keep it uniform and close to 1 but this really is impossible to do accurately without combining the SFS DEM with another DEM created using stereo imaging. A lot of stereo coverage is available but I haven't done this yet since it takes a lot of time - I may do it later. Vertical exaggeration probably tends to be greater in the highest resolution patches than in the lower resolution areas. It should be noted that for Enceladus I used a uniformly white texture map, i.e. all of the details visible are from the DEM. Compared to the source images, resolution loss is minimal in the DEM.

There is probably sufficient medium to high resolution data available to make a global DEM with one exception: The north polar region. Hopefully Cassini manages to completely image the NPR at 300-500 m/pixel (or better - preferably 100-300 m/pixel) later in its mission.

A few sample frames:

Attached Image
Attached Image

Attached Image
Attached Image

Needless to say I recommend fullscreen viewing (and a biased comment: Looks awesome on a large TV screen).
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Posts in this topic
- Bjorn Jonsson   Enceladus PDS image products   Jul 22 2010, 03:22 PM
- - charborob   I must be missing something in my version of Quick...   Jul 22 2010, 03:47 PM
- - Bjorn Jonsson   I forgot to mention that to play the animation you...   Jul 22 2010, 03:55 PM
- - Floyd   Very nice! And thanks for the directions to t...   Jul 22 2010, 06:16 PM
- - lyford   Beautiful - thank you!   Jul 23 2010, 12:46 AM
- - nprev   ...outstanding, Bjorn, thank you!!!   Jul 23 2010, 01:59 AM
- - Ian R   Very well done!   Jul 23 2010, 03:43 AM
- - JohnVV   very nice it is time consuming isn't it by...   Jul 23 2010, 09:41 AM
- - Bjorn Jonsson   Yes, finishing the DEM is time consuming - it...   Jul 23 2010, 07:18 PM
- - Bjorn Jonsson   After seeing machi's anaglyphs of Titania I de...   Apr 19 2011, 02:10 AM
- - machi   Very nice! I'm glad, that my work is inspi...   Apr 19 2011, 11:27 AM
- - Phil Stooke   Right... approaching the south pole with the plume...   Apr 19 2011, 03:14 PM
|- - Bjorn Jonsson   QUOTE (Phil Stooke @ Apr 19 2011, 03:14 P...   Apr 20 2011, 11:06 AM
- - machi   Superb work! Can you make this animation in r...   Apr 20 2011, 12:29 PM
- - Bjorn Jonsson   As I have mentioned, I'm working on a DEM of E...   Jun 28 2011, 08:46 PM
- - volcanopele   Not bad, not bad at all. You did better at blendin...   Jun 28 2011, 10:23 PM
- - Ian R   That's top-drawer, Bjorn. Simply top-drawer.   Jul 1 2011, 04:09 PM
- - machi   Feast for the Eyes!   Jul 1 2011, 06:26 PM
|- - tedstryk   Wow...Bjorn, that is all I can say, wow. Great wo...   Jul 2 2011, 03:05 AM
- - ElkGroveDan   Bjorn knows more than a little bit about ice.   Jul 2 2011, 03:35 AM
|- - Bjorn Jonsson   QUOTE (ElkGroveDan @ Jul 2 2011, 03:35 AM...   Jul 3 2011, 11:24 PM
- - elakdawalla   Are you using ISIS on a Mac or running Linux?   Jul 4 2011, 02:13 PM
|- - Bjorn Jonsson   QUOTE (elakdawalla @ Jul 4 2011, 02:13 PM...   Jul 4 2011, 02:17 PM
- - djellison   On a Mac, apart from having to use the terminal to...   Jul 4 2011, 02:21 PM
- - machi   Beautiful!   Oct 5 2011, 06:53 PM
- - Phil Stooke   agreed! Phil   Oct 5 2011, 09:01 PM
- - ngunn   An all time classic. That deserves wide circulatio...   Oct 5 2011, 10:23 PM
|- - ugordan   Thanks. BTW, if that image looks slightly ...   Oct 5 2011, 10:36 PM
- - Stu   Absolutely beautiful. Seriously, why your images a...   Oct 5 2011, 11:21 PM
|- - djellison   QUOTE (Stu @ Oct 5 2011, 04:21 PM) and on...   Oct 6 2011, 12:41 AM
- - eoincampbell   Wondrous !   Oct 6 2011, 02:09 AM
|- - ugordan   Subject: Enceladus plume temporal variance. 3 NAC ...   Oct 10 2011, 08:33 PM
|- - ugordan   Here's a ratio flicker gif. First frame is fra...   Oct 10 2011, 08:43 PM
|- - machi   QUOTE (ugordan @ Oct 10 2011, 10:33 PM) S...   Oct 10 2011, 10:08 PM
|- - john_s   QUOTE (ugordan @ Oct 10 2011, 02:33 PM) S...   Oct 12 2011, 02:34 AM
- - ngunn   I'm not sure if it's two variable vents or...   Oct 10 2011, 09:01 PM
- - eoincampbell   Has the long shadow been explained?   Oct 11 2011, 02:49 AM
- - nprev   Re the long shadow: Looks to me like that's pr...   Oct 12 2011, 10:22 PM
- - hendric   Isn't that mostly Saturnshine lighting up the ...   Oct 13 2011, 06:24 PM
- - Bjorn Jonsson   This is a 21 frame mosaic of images obtained durin...   Nov 15 2011, 09:54 PM
|- - tedstryk   QUOTE (Bjorn Jonsson @ Nov 15 2011, 09:54...   Nov 16 2011, 05:59 PM
- - Juramike   Wow! The detail in that image is fantastic...   Nov 16 2011, 01:02 AM
- - Guillermo Abramson   Amazing. Thanks for sharing it. Guillermo   Nov 17 2011, 01:37 AM
- - scalbers   Greetings - thought I'd post my latest Encelad...   Feb 25 2012, 06:07 PM
- - elakdawalla   These are cool, Steve! Thanks for sharing. R...   Feb 26 2012, 10:18 PM
- - scalbers   Thanks Emily. Here's an updated version where ...   Feb 27 2012, 07:51 PM
- - Bjorn Jonsson   My latest animation: Flight over Enceladus This ...   Mar 4 2012, 08:14 PM
|- - Zack Moratto   QUOTE (Bjorn Jonsson @ Mar 4 2012, 12:14 ...   Mar 9 2012, 10:44 PM
- - scalbers   Very nice animation Bjorn. It's fun to try and...   Mar 4 2012, 08:38 PM
|- - ugordan   QUOTE (scalbers @ Mar 4 2012, 09:38 PM) M...   Mar 4 2012, 08:47 PM
|- - Bjorn Jonsson   QUOTE (scalbers @ Mar 4 2012, 08:38 PM) V...   Mar 5 2012, 10:10 PM
|- - FordPrefect   QUOTE (Bjorn Jonsson @ Mar 5 2012, 11:10 ...   Mar 13 2012, 01:01 AM
|- - Bjorn Jonsson   The modified Hapke function I'm using can be f...   Mar 17 2012, 12:47 AM
- - machi   It looks fantastic Bjorn! Can you make some an...   Mar 5 2012, 10:21 AM
- - JohnVV   nice It might be my imagination but did you use ...   Mar 6 2012, 06:24 AM
- - Bjorn Jonsson   I used ISIS' dstripe 'indirectly' - th...   Mar 6 2012, 11:44 PM
- - Bjorn Jonsson   Not a list but the March and July 2005 flybys prov...   Mar 10 2012, 01:34 PM
- - PDP8E   Bjorn, That flight was tremendous! Thanks for ...   Mar 10 2012, 05:14 PM
- - Ian R   I'll second that.   Mar 11 2012, 08:47 PM
- - FordPrefect   Thank you very much Bjorn for the insight!   Mar 17 2012, 01:58 PM

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