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Enceladus PDS image products
ugordan
post Feb 9 2012, 11:27 AM
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QUOTE (dilo @ Feb 8 2012, 09:19 AM) *
Congratulations to Gordan for today's APOD mosaic, it is really stunning!
http://apod.nasa.gov/apod/ap120208.html
(I would like to see more in the plume region but I guess wasn't photographed).

Thanks, but that doesn't really belong to this thread. The image (not a mosaic) was taken a year ago.

Thanks for pointing this out. Posts moved to the correct thread - moderator


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scalbers
post Feb 25 2012, 06:07 PM
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Greetings - thought I'd post my latest Enceladus feature map here:

Attached Image


(Note to mod, technically this includes some PDS and older raw images, so the best thread/forum for this might be considered)


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elakdawalla
post Feb 26 2012, 10:18 PM
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These are cool, Steve! Thanks for sharing. Regarding where they should be put -- the point of the "raw" threads is to discuss ongoing mission in real time (the way the MER threads work), "PDS" threads are about manipulation of data sets. You've posted in the right place.


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scalbers
post Feb 27 2012, 07:51 PM
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Thanks Emily. Here's an updated version where more of the feature labels are rotated and offset for the Dorsa, Fossae, Sulci and such...

Attached Image


Full Resolution here: http://laps.noaa.gov/albers/sos/features/c..._180_center.png

That's the latest,

Steve


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Bjorn Jonsson
post Mar 4 2012, 08:14 PM
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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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scalbers
post Mar 4 2012, 08:38 PM
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Very nice animation Bjorn. It's fun to try and recognize various features as you fly over. One example is the sequence starting at 4:55 when the crater Sabur is centered in the view. Then from 5:00 to 5:12 we are flying northbound alongside Anbar Fossae. At 5:21 we're transitioning from Samarkand Sulci to Hamah Sulci (note unnamed crater at that time), then about 5:30 when flying from Hamah Sulci down to Ebony Dorsum.

Earlier at 2:23 we come upon a double crater, the one on the right side being Al-Mustazi. We approach the northern part of Bishangarh Fossae at 2:26. Then we catch the western part of Al-Yaman Sulci (oriented from left to right) around 2:33. By 2:43 we swing to look at the southern end of Harran Sulci (towards the west). At 2:49, we are looking westward at the northern end of Khorasan Fossa. At 3:00 we spot the intersection of Harran Sulci and Kaukaban Fossae near the limb. Then by 3:07 the crater Harun is located above the center. The southbound canyon fly through at 3:30 looks like we're going back through the southern end of Harran Sulci.

Perhaps the makings of a narrated sound track?

Things like the serrated limb help to make this look very realistic. Might be interesting to consider texture and even some slight color at some point?

Steve


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ugordan
post Mar 4 2012, 08:47 PM
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QUOTE (scalbers @ Mar 4 2012, 09:38 PM) *
Might be interesting to consider texture and even some slight color at some point?

On the contrary, I think Bjorn nailed the color here. wink.gif

Interesting to watch the phase angle effects as well, it's clear right from the initial frame that the photometric modelling of the disc is more realisic than what one would expect from just illuminating a ball in a commercial 3D renderer. About the only thing that gives away the fact this is a rendering is the lack of secondary illumination of shadowed slopes near the terminator by the opposing sunlit slopes. Other than that, add some point spread function and this could pass under an actual Cassini image.


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machi
post Mar 5 2012, 10:21 AM
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It looks fantastic Bjorn!
Can you make some anaglyph versions?


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Bjorn Jonsson
post Mar 5 2012, 10:10 PM
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QUOTE (scalbers @ Mar 4 2012, 08:38 PM) *
Very nice animation Bjorn. It's fun to try and recognize various features as you fly over. One example is the sequence starting at 4:55 when the crater Sabur is centered in the view. Then from 5:00 to 5:12 we are flying northbound alongside Anbar Fossae. At 5:21 we're transitioning from Samarkand Sulci to Hamah Sulci (note unnamed crater at that time), then about 5:30 when flying from Hamah Sulci down to Ebony Dorsum.

[snip]

Perhaps the makings of a narrated sound track?

Things like the serrated limb help to make this look very realistic. Might be interesting to consider texture and even some slight color at some point?

Steve

A narrated sound track - that's an interesting idea. And it's nice to see there are lots of recognizable features there ;-). Regarding texture, it wouldn't add any details since compared to the original images, loss of resolution is negligible in the DEM.

QUOTE (ugordan @ Mar 4 2012, 08:47 PM) *
Interesting to watch the phase angle effects as well, it's clear right from the initial frame that the photometric modelling of the disc is more realisic than what one would expect from just illuminating a ball in a commercial 3D renderer. About the only thing that gives away the fact this is a rendering is the lack of secondary illumination of shadowed slopes near the terminator by the opposing sunlit slopes. Other than that, add some point spread function and this could pass under an actual Cassini image.

I'm using a slightly modified version of the earliest Hapke function - it's modified to avoid unrealistic effects when the emission angle approaches 90 degrees. The phase effects are interesting and very strong. I even had to reduce the opposition effect a bit to avoid problems with dynamic range.

The lack of completely black shadows (no secondary illumination) is a problem and makes terminator closeups less realistic. The only reason I avoided them was to speed up the rendering time. Adding a point spread function is a nice idea but some of my test renders look realistic to me anyway. A year or two ago I somehow managed to confuse an Enceladus test render with a Cassini image for a few seconds. Needless to say I was happy when I realized what had happened.

QUOTE (machi @ Mar 5 2012, 10:21 AM) *
It looks fantastic Bjorn!
Can you make some anaglyph versions?

That's probably a bit complicated due to the complicated flight path. A bigger problem is rendering time even though my renderer is at least two times faster now than it was two months ago. But this might be an interesting future project.
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JohnVV
post Mar 6 2012, 06:24 AM
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nice
It might be my imagination but
did you use ISIS to " destripe "
I have been reprocessing the venus data and have been seeing that X cross hashing every where
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Bjorn Jonsson
post Mar 6 2012, 11:44 PM
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I used ISIS' dstripe 'indirectly' - the dstripe documentation contains a fairly detailed description of the algorithm used to destripe and this enabled me to implement this capability in my own software. I've mainly been using ISIS to correct the camera angles (jigsaw, deltack etc.).

Regarding the "X cross hashing" - if this is what I think it is I've seen it too. I've found that fairly often after I destripe, new narrow and fainter stripes appear that have an orientation that differs from the orientation of the original stripes. When this happens I need to rotate the DEM (to make the new stripes horizontal), destripe again end rotate the DEM back. Sometimes I need to do this several times. Sometimes this is a prolonged trial and error process.
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Zack Moratto
post Mar 9 2012, 10:44 PM
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QUOTE (Bjorn Jonsson @ Mar 4 2012, 12:14 PM) *
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.


Do you have a list of stereo pairs that could be processed? ISS images usually process pretty quickly in ASP and would make a fun test case for me. I could then share my results back to you via this thread.
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Bjorn Jonsson
post Mar 10 2012, 01:34 PM
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Not a list but the March and July 2005 flybys provided lots of stereo coverage since there is a lot of overlap - the March flyby was equatorial and the July flyby south of the equator with the illumination geometry almost identical.

Stereo pairs from these flybys are easy to find - one example is images N1500059045_2.IMG (July) and N1489045316_2.IMG (March).

There is also stereo coverage from later flybys but I'm not yet familiar with the details of these flybys.
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PDP8E
post Mar 10 2012, 05:14 PM
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Bjorn,
That flight was tremendous! Thanks for sharing your hard work.
You and your work are an inspiration.

~pdp8e


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Ian R
post Mar 11 2012, 08:47 PM
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I'll second that. blink.gif


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