Thanks for sharing your insights into the photoclinometry from radar images. It's one of those things that seems obvious at first but is quite the opposite. At least I learned something!

Thank you all so much for all the nice words and suggestions !

At this time, the project is unfortunately not yet ready to be officially released in any publicly useable way for several reasons. First, it is still in a very early stage of development and I have just begun to explore the possibilities and there are a lot of ideas for improvement that I would like to try out, many bugs to be fixed etc.
Also, there are technical and license related obstacles : for example I am using a large collection of self written and third-party C/C++ APIs and libraries that I developed and collected over the past 15 years.
While some of them are open source, there are also commercial or closed source libraries that would have to be completely re-written first. (this task alone would be a several-years project I'm afraid)
And most importantly, there is no such thing like a GUI or comfortable user interface. The whole project is more like an experimenting platform consisting of a complex & ugly command line interface, a cryptic shell language and about 2000 tuning parameters ...
Also, I am doing this all in my spare time only, as a means of recreation and relaxation ...
And for me it is simply much more fun to explore and implement interesting algorithms without taking care to write clean and robust user interfaces, doing customer support or the like (this is what I have to do in my profession as software developer all the time

Finally I view my software projects mainly as tools, i.e. the means for creating atmospheric images and it is those images that are the real "publishable end product" of the whole process. The algorithms and software are just the "painters brush and easel" or the photographer's camera so to speak.

So at the very least I will continue to publish those images on a regular basis ... maybe I even find the time to setup a Web Gallery or Blog for that purpose.

As should already be obvious I'm very interested in this so there are some things I'm curious about. From the examples posted it looks as if something like this might revolutionize the quality and resolution of my stereo derived DEMs where the low frequencey stuff is already reasonably accurate. I have already figured out how I would combine stereo DEMs and SFS DEMs.


Is this (commercial/closed source libraries) a problem because it's explicitly forbidden to distribute software based on them or is the problem licence costs or stuff like that? Vikingmars' idea (donations) is interesting and the reason I ask. There's nothing that says the software must be freeware if you make it available one day (and obviously that wouldn't work at all if library licence costs are an issue).


How important this is depends on the 'type' of users. Almost all of my software is command line utilities, including the stereo software - doing a nice GUI is a waste of precious time ;-). For lots of users this might be a problem though.


Now this is something familiar (and lack of time is too ;-)).

I should add that despite the questions/comments above I'm not surprised you are not interested in immediately releasing this. My stereo software is in a similar state as far is this is concerned - it works but there are some bugs and quirks I know of. For example it currently works only for images from framing cameras - using pushbroom source images would probably result in distorted DEMs (I haven't tried it though).

I'm wondering if you (Bernhard) can run your software on the picture included here: http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2638.pdf from Phil's post regarding Oppy traverse.
Seing some relief and visualizing what will be seen once at the "hell of a view" point, in another 2 kms, will surely be very much appreciated here.
Let us know.
Thanks

It can't be done on that image, it would have to be on the original CTX or HiRISE images.

But of course, seeing these great results for the Columbia Hills or Endeavour crater would be very much appreciated!

Phil

I have been thinking about that, too. Do you have the HiRISE/CTX observation IDs for the best/highest resolution images of this areas ?
(I could not find them in the mentioned paper)

Two for the columbia hills are listed within this DTM
http://hirise.lpl.arizona.edu/dtm/dtm.php?ID=PSP_001513_1655

Ah, thanks. Here is a quick try with my single-image-SFS-DEM at a 3D zoom into the Columbia-Hills HiRISE image linked above:

2D version (at maximum HiRISE resolution)
Click to view attachment

Generated 3D version (with approx. 3 millions of shaded polygons)

Click to view attachment

Note that the above image is for visualization only. There may be distortions in the map caused by albedo differences (due to dust coverage patterns, for example ) that the single-image algorithm can not resolve.

The original recently published HiRISE DTMs of which I also rendered a qick visualisation (over a larger area)

Click to view attachment

are much more accurate with respect to the mid and large scale height variations.

Still, for visualization purposes I like the high-resolution detail, almost photographic look of the single-image based DEMs
(It's a lot of fun to be able to "wander-into" the landscape from a single 2D image only

Nirgal, I can't find your original thread so I'll add on here. I have a request. Can you work your magic on these features. They are located just inside Endeavour crater and are a possible destination for Opportunity. Contour maps seem to bypass them yet they look as if they have some relief:

http://www.unmannedspaceflight.com/index.p...st&id=16180

Interesting. I will see what can be done with these (although from first glance there seems to be large albedo variations in the terrain)
Do you have the original HiRISE observation ID for the image ? (will be useful for obtaining the viewing parameters needed to optimize the 3D reconstruction process)

No I don't, unfortunately. Go to the 'Endeavour crater, and again we shall conquer the remoteness' thread post 105 and following and you will find all I have on this. Others here may be able to help more.

AFAIK, that's the non-map-projected version of PSP_010341_1775.

Upon a request posed over at the "Dust Avalanche" thread I did a small 3D DEM study of an area near Endeavour Crater based on a single image cropped from PSP_010341_1775.



Click image to see the whole gallery. The first image shows the DEM rendered from above with the same lighting conditions as the original image so as to give an idea of the accuracy of the 3D reconstruction (note, however, that the accuracy decreases somewhat when the DEM is lit from other than the original lighting direction).

The generated DEM consists of 8192x4096 = 32 million polygons with true 3D (means no texturing) post spacing at full HiRISE resolution (28.6 cm/pixel ).

Here is my usual Disclaimer: the rendered DEMs are intended for visualization only. The absolute heights are not calibrated and there may be distortions due to albedo variations.

YES!! Now that is everything I'd hoped for and more. Enormous thanks Nirgal. Can you say if there is vertical exaggeration there, and if so how much? This does indeed look like a most worthy target for Opportunity.

(thanks Tesheiner also for undoing my thread tangle)

Incredible!

BTW, I think we'll have to save this picture, bookmark this thread / post, and revisit it in about one year to compare it with the "ground truth".

I can not give an exact answer to this one as I do not usually put much effort into calibration of abolute heights (for my visualization purposes it's sufficient that the rendered DEM looks approximately the same as the original 2D image when viewed and illuminated under the same conditions )
Then I do have a switch, called "Z_scale_factor" that I sometimes use to exaggerate (or attenuate) the heights artificially. in this case the factor was 1.3 so there is some exaggeration (just for better emphasis of terrain variation) but moderately so.

This area has fascinated me for a while and Nirgal's renders have crystallized some of my thoughts. Since I'm a sequence stratigrapher by trade and training (and some say religion...), I look at strata in terms of their geometry (shape and topology of the boundaries) and where and how they terminate. The method of tracking stratal terminations originally comes from interpreting seismic profiles (seismic stratigraphy) where one traces the continuity and termination of reflections. Through this, relative ages, directions of transport, subsidence patterns patterns and other cool things can be determined. Among other types, some of the most obvious stratal terminations include onlap, downlap, and truncation. These little schematic cross sections show the geometry of onlapping and downlapping strata:

Click to view attachment

In the image from Nirgal below, I've highlighted several areas of stratal terminations in one of my (in)famous 5 minute speed interpretations:
Click to view attachment
red: onlap
blue: downlap
white: truncation by channels

The slightly sinuous channel on the right side of the image does some really cool things, including exiting the terrace region at the top of the image through a v-notched canyon. It suggests the channel is a subsequent geomorphic feature that has incised into previously buried strata as the landscape has been regionally degraded (think Colorado Plateau, Canyonlands, Grand Canyon, etc.). The raised lip of the terrace on the right is also intriguing (due to channel incising?, differential erosion?, etc.)

In general, the hill looks like it was a preexisting topographic feature that was onlapped by several periods of deposition, including the terrace unit which seems to have formed as an apron of downlapping strata that prograded away from the hill (like a shoreline). Subsequent regional landscape degradation has exposed various levels in the stratigraphy which allows us to examine the relative timing and geometry. The degradation has included a channel-incisement phase that has cut through most of the units and has been guided by the differential erodibility of the strata.

Ground truthing these interpretations when Opportunity get here, especially examining the depositional nature of the units and the relative timing of deposition and erosion, is going to be very interesting!

Fascinating interpretation there, thanks for sharing. There is one note of caution I'd like to sound in relation to small details of these images - it may be wrong and if so I hope Nirgal will correct me. He himself pointed out that albedo differences could affect his results here. In particular the 'beach terrace' is lighter toned than most of the rest of the scene. I think this might account for its edge looking different on each side of the hill, depending on the original direction of illumination. Funnily enough this difference was the first thing my daughter remarked upon when I showed her the images. Is it real or not? I'm not sure.

I have another question. What is the elevation of the 'beach terrace' and how does it compare with the lowest elevation on the perimeter of Endeavour? I think they're fairly close.

Me too. I've been drooling over it. Thanks Tim for your nice clean interpretation and diagram. A lot of it fits my thinking, though I was scratching my head about that channel on the north end.

A question for Tim and Nirgal: This is one of the hills on the western edge of Endeavour? If so, Tim's comment "In general, the hill looks like it was a preexisting topographic feature that was onlapped by several periods of deposition" refers to geologic changes much after formation of the crater? I assume the hill was created by the impact and was not there prior to the impact. Sorry for my confusion.

Zoomable CTX of the area:
http://global-data.mars.asu.edu/ctx/img/P0...1780_XI_02S005W

Looks like the next hill to the south has similar features at its northern end (Nirgal??? )

Correct. that's why I usually add my "for visualization purposes only" disclaimer
without knowledge of the true albedo variations, it's difficult to interpret the apparent height variations.



actually it's quite the opposite: the smaller the detail, the better the accuracy of the 3D reconstruction (look at how the small craters and mini dune ripples got reproduced) because albedo variations occur more at larger spatial scales.
That's why the photoclinometric method can nicely complement the mult-image stereo-based methods that are less accurate at the very finest scale (you need features spanning areas of multiple pixels for the point matching algorithm) but are not so easily tricked by albedo variations.
So as mentinoed before: the real potential of the method for scientific usage could only be exploited by combing it with stereo/altimeter based data.
That being said: it is surprising how well the single-image reconstruction often works even in presence of albedo differences and cast shadows (see for example the dark dust steaks over the fine dune ripples in the image posted at the other thread) However, while often working pretty well, there is unfortunately no guarantee so (I have also encountered examples where the albedo problem messed up the 3D reconstruction completely )

I'm sure we will have an official stereo-based HiRISE DEM at 1m/pixel reslution of this area soon.
Then I can try to combine the 1m/pixel stereo-DEM it with my 25cm/pixel photoclinometric DEM to possibly get the best out of both worlds ...

But until then I reiterate my note of caution with respect to scientific/geologic interpretations based on the single-image DEMs that I want to be understood mainly as a means of visualization rtaher than a measurement tool ...

However, it's totally ok and a pleasure for me to see that the visualizations help to spark new and crystalize previously existing ideas... But for such ideas to be finally proven, I think we will need the real ground truth data in the end.

For comparison, here is (a crop of) the original, radiometrically calibrated HiRISE-image I used as input for the 3D reconstruction algorithm (all images at half resolution) A:
Click to view attachment
which yields the following DEM (greylevel = height) B:
Click to view attachment
Now, once I have the DEM I can re-render it under exactly the same illumination conditions (incidence angle, sub-solar azimut etc.) as the original image, which yields this view: C:
Click to view attachment
So comparing A and C gives an idea of the accuracy of the reconstruction process (as can be seen, the so called "photometric error" is almost zero). However, the low photometric error does not tell the whole story because it does not address the albedo variations which can not be resolved from a single image alone without additional information.
The comparison shows, that the reconstruction can be quite exact, at least in the absence of albedo variations...
(The increased contrast in C is due to the higher dynamic range of greylevels used by the 3D renderer compared to the somewhat hazy original image)

To me it looks like an' island' which eventually got surrounded by lava!Very much like the Columbia Hills in Gusev Crater.So the elevated unit(part of crater rim) should be an older geologic unit compared to the lower areas surrounding it.Any idea as to minerals identified in this unit??

Yes indeed similar. here are some detail 3D views of the northern end of the next hill to the south.
No vertical exaggeration this time. alternatively I rendered the DEMs with a simulated lower sun angle (i.e. later evening view) than the original in order to pronounce the terrain variations

Click to view attachment
Click to view attachment
Click to view attachment

Here is a "Fly-over-view" from the south (north is up) showing the whole "atoll-like" hill complex:

Click to view attachment

Again, greatly appreciated Nirgal. Those ones show nicely how as it trends north the line of hills dips downward inside the internal crater slope and so will remain out of sight until we get much closer.

Nirgal, on closer inspection I'm having trouble with your last image there. Is it left-right inverted?

You are right: somehow the last image got mirror inverted - which is confusing so I changed it. now it's north=up east=right as usual ...