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Author Topic: Mars DEM/Orthoimagery Co-Registration and Procedural Environment Considerations  (Read 5710 times)

Uriah

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  • We do these things not because they are easy. -JFK

I read (http://tinyurl.com/l2puzas) that OT is having difficulty with the DEM and orthoimagery datasets of Mars being out of alignment. I have spent considerable time attempting to co-register them manually in the past, to no avail. What is needed is software such as ENVI in order to perform Automatic Co-Registration of the two images. I can call up my friend at NASA and see if he can put me in touch with someone how has co-registered datasets, or knows how to.

I also have some suggestions, which may have already been covered or not, in regards to how the procedural environment of Mars differs from Earth.

Procedurally Mars is both easy and it is hard. While there is no vegetation, many people believe there is no running water to speak of. While there isn't much apparently, flash melting of ice beneath the ground does erode the landscape, and in its past Mars had a vast ocean, so water erosion is evident everywhere. That brings me to my point about procedurally generated craters and what shape and profile they must have in different Mars biomes.



Looking at the elevation map we can automatically identify two distinct biomes, Ancient Ocean bed, and... everywhere else. One key distinction, is the lack of large crater impacts below the Ancient Sea level. Of course the ocean absorbed all but the most colossal impacts. Therefore, procedurally generated craters, of micro to medium size in the Ancient Ocean biome, must be newly formed. And as a rule of thumb, there will be far more bigger, older, more weathered craters in areas where the ancient ocean didn't cover. This is extremely important as far as realism goes for Mars.

We can visibly infer the age of a crater by its shape and profile. If it has a sharp edge, and deep-concave impact crater, it is newer. If the edges have been worn away considerably, and the bottom of the crater flattened out due to sediment deposits, it is much older. There is wind on Mars which accounts for considerable erosion of craters. Since the frequency of larger impact is far far less, a vast majority of large craters will be old and worn down, and far more of the micro-meteor craters will be new. This also needs to find its way into the OT algorithm.



Another variable to include in crater generation is the inclination of impact. Epitomized by this 48 mile long elliptical crater, once in a while an impact occurs as a shallow angle, and the resulting crater is greatly elongated. Probabalistically speaking, most impact craters are circular having hit at a much steeper angle with more kinetic energy delivered to the ground as impacts at a low angle will spend more time in the thin Martian atmosphere during Mars capture, and therefore will be traveling at a lower velocity upon impact. Again, not always the case, so there is your random, probabilistic factor to kick in every once in a while.



Also, recent impacts still bear clear kinetic evidence, this would make a nice texture enhancement for micro meteor impact craters that are procedurally generated! Micro meteor impact are a common occcurance on Mars while nothing that small can reach the ground on Earth because Mars has 1% of the atmosphere. An object the size of a peanut traveling a those speeds will make a sizable crater.



...and while I am at it, I want to make sure OT is going to get it right from the get go. Build a solar system model, and make sure that JSBSim can run real-world orbital mechanics for interplanetary flight. If OT gets all this way but doesn't get orbital mechanics right, it would be a real shame. It would be really super extra ultra deluxe if Lagrange points worked (L1, L2, L3, L4, L5), but I'm a beggar not a chooser in this respect. :D

I am working on a rocket sim mod for Outerra, called AeroKinetics (http://forum.outerra.com/index.php?topic=3062.0), and I am counting on you guys!

Regards,
Uriah
« Last Edit: November 28, 2014, 06:37:30 pm by Uriah509 »
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Uriah

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A personal favorite, HiRISE image of the Tantalus Fossae Crater which indicates two very different densities in the ground. The impact crater is deeper in the less dense ground, and more shallow in the denser harder ground. Natural erosion has also had the very same affect around the crater. Fascinating image!



Look how perfectly flat the bottom of the crater has become. It is a small crater, as you can see from this image.

« Last Edit: November 28, 2014, 06:36:01 pm by Uriah509 »
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PytonPago

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  • It´s way too complex, dont let me try to explain !

Well, craters may be just implemented purely trough terrain data, ill see finding and aligning biome information (ground types and theyr colors) well enough as a possible problem. But Cameny wrote a quite whyle ago, that he would like to add biome and weather enhancements in manner of terrain deformations (making tracks in overly soaked grounds and sand, and maybe with proper resistance for vehicle physics). Would be quite a thing, if the crater gun generator could be tuned for different types of ground proprieties, making it be deformed due to the ground resistance differences. It would be also quite a thing in choosing bad landing places for inter-planetary crafts, if in last meters it would affect the trust distribution, or vehicle being tilted/stuck at edges of softer grounds.
Im sure the Moon will probably have something of this too as for the hardened magma seas of it. What might be tricky doe, is the fine dust in and around the craters - when the material set aground after impact, there is a slight layer of it varying on the crater character mass displacement volume (yest, just for fresh craters, but NASA might have a index of such). If they could add something like this onto the biome/ground property layers ... well awesomeness itself. ( nothing better like simulating full flight from earth to mars getting stuck or flipped at the journeys end in some tricky sediment, just like crashing a plane at landing after a well done flight ::) ).
« Last Edit: November 28, 2014, 04:53:38 am by PytonPago »
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.

Uriah

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  • We do these things not because they are easy. -JFK

I might be about to co-register the data sets for you! :)

I saw a comment where someone asked if you could make "inverted rocks", I think he meant sink holes. I believe the same algorithm that is used to implement rocks can be inverted and used to make different concave shapes in theground.

I am just saying, the biggest difference between the surface of Earth and Mars is the shape of the micro topography. There are small 1 m to 20 m craters all over Mars. I believe this would be one of the most effective ways of making Mars look realistic. I can provide NASA crater data if you would like.

Regards,
Uriah

P.S. A few of my images from Google Drive didn't show before, they do now.
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PytonPago

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  • It´s way too complex, dont let me try to explain !

While topography is in debate ... i couldn't just not post this after seeing it.



Doe, drinking deuterium water is quite a bad idea for potential Mars-mission participants, its so much interesting in terms of chemistry that such a little weight-difference between normal water and its deuterium brother is enough to keep it in the Marses surroundings, even after such gradual atmospheric change. ( basically, 16 g/mol vs roughly 17 g/mol, imagine, just one gram on 6,022x10e23 molecules of water ! ) Their mass-estimation of the ancient Marses water is based on the Earths ratio of water/Dwater. Its also curious that the water was almost all on just one hemisphere. I wonder how water and wind circulation in global scale would have looked like back then on Mars ...

 ... hope we could one day try render that water level on Mars in OT. :D
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.