Experimental Rhea DEM animation, Generated from stereo images Options

[malgar]

I've been frustratingly close to generating DEMs of Saturn's satellites for some time using my own software that generates DEMs from stereo pairs. The problem is that the resulting 'DEMs' are far too noisy and contain too many spurious features and artifacts to be useful. If just this $%#€% thing worked as I want it to I would also be able to generate DEMs of Mars using two images (a stereo pair).
http://www.unmannedspaceflight.com/index.p...3&hl=stereo

Hello Bjorn! I wrote myself a software that generated DEMs from stereo pairs. It isn't perfect but noise isn't so high in most of the images.
I posted a work on the Moon section of this forum.. check here: Stereo from Apollo
Can you give me your stereo pairs where you tested your program?



Ciao,
Alessio

[Bjorn Jonsson]

This looks very impressive but it would be very interesting to see this same rendering without any texture draped over it (or even to see the DEM itself). I have noticed that a texture draped over a DEM adds a great deal of realism and also 'hides' many of the unwanted DEM artifacts ('contours' and noise).

I will post the images I used as stereo pairs in a day or two, I'm away from my main computer at the moment. It would be interesting to see how your DEM compares to mine.

BTW I will probably be posting a DEM covering a significant fraction of Mimas' surface within a week.

[malgar]

This looks very impressive but it would be very interesting to see this same rendering without any texture draped over it (or even to see the DEM itself). I have noticed that a texture draped over a DEM adds a great deal of realism and also 'hides' many of the unwanted DEM artifacts ('contours' and noise).

You have right, for example as I said in the Apollo thread, I used a low resolution (50px) to avoid noise and then interpolated to 1 px. Only larger features are visible. A better resolution shows smaller carters but noise is a bit high. The left border doesn't show the ridge of the big crater.
It works but it could be much better. I would be glad to share each other ours code and work together. Two is better than one. If you want..

In the attachment (half size due space limitations) the original image and the DTM.

Alessio

[Bjorn Jonsson]

Can you give me your stereo pairs where you tested your program?

The two images of Herschel I used are these ones:

http://www.mmedia.is/bjj/3dtest/rhea_dem/N1501625473_1.png
http://www.mmedia.is/bjj/3dtest/rhea_dem/N1501627117_1.png

Viewing geometry:
N1501625473_1.png
Subspacecraft lat=-24.5768010
Subspacecraft lon=127.6508400
Range=251180 km
Subspacecraft line sample=558.331660
Subspacecraft line=397.742371
North azimuth=269.274119

N1501627117_1.png
Subspacecraft lat=-25.2006590
Subspacecraft lon=133.7466500
Range=227797 km
Subspacecraft line sample=476.255632
Subspacecraft line=507.076670
North azimuth=269.235065


For Rhea I used these images:
http://www.mmedia.is/bjj/3dtest/rhea_dem/N1484600736_1.png
http://www.mmedia.is/bjj/3dtest/rhea_dem/N1484607379_1.png

Viewing geometry:
N1484600736_1.png
Subspacecraft lat=-12.3275880
Subspacecraft lon=97.8282730
Range=172101 km
Subspacecraft line sample=341.191670
Subspacecraft line=-146.888170
North azimuth=0.220007

N1484607379_1.png
Subspacecraft lat=-13.5285270
Subspacecraft lon=113.2800300
Range=185439 km
Subspacecraft line sample=426.510190
Subspacecraft line=-193.320590
North azimuth=0.177863

The field of view is 0.351549 degrees.

In all cases I have modified the subspacecraft line sample and the subspacecraft line values from the values in the PDS-released files.

[Bjorn Jonsson]

Here is a fairly big DEM of Mimas:



This is a section of a 1800x900 pixel simple cylindrical map. It covers latitudes -76.6 to 47.6 and longitudes 158.4 to 283.2. The distance from Mimas' center ranges from 186.8 (black) to 209.6 km (white).

This DEM is a mosaic of two DEMs derived from one stereo pair each. One problem is immediately apparent: A ~2.5 km altitude difference near the left edge of the seam. This is due to viewing geometry errors. I am using significantly more accurate viewing geometry parameters than in the PDS files but they are still not accurate enough. At the moment I don't know how I'm going to correct this.

Comparing this DEM to the DEM of Rhea is interesting, for example comparing the crater depth/diameter ratios.

[um3k]

At the moment I don't know how I'm going to correct this.

High pass filter!