Dilo said: "Many will recall my route maps of Erebus highway I did using this technique;"

Yes, they were excellent. I would like to see more of them.

Indian3000, your latest work on polar projections would be another very good way to do this, if you could add an option to project the polar view onto a plane and specify the x,y limits of the view. Your first software contribution did the same but in a more complex way, taking the 3D topography more fully into account and linking it to rover motion. But a quick way to get to a similar view might be very useful.

Phil

Phil: Yes, I remember those fine maps from Dilo. I wish I could find an easy way to make them, but an easier solution would be for Dilo to bring them back every once in a while. I investigated POV-Ray a while ago, but being a code-challenged person I concluded that I might eventually make it work, but I wouldn't have any time left to do anything else. I'll keep hoping for something like a POV-RayGUI.
Oh, yes. I'm hoping they will kick that up to more like 75 meters/day, now that they've tested the waters.

Regarding the distinction between a ripple and a dune, I think it is a difficult distinction. Inherently, we suspect the distinction should be something simple like a height or wavelength threshold. Very crudely, dunes are larger and ripples are smaller. That is why I prefer O'Doug's proposed term, "drift." There are a lot of variables which affect the movement of particles by the wind, and which control the size and shape of the landforms we see. There are others here who are much more knowledgeable than I am about this subject, but since several have asked about it, and because I have been trying to learn more about it, I'll throw this out.

If anyone is willing to invest some time reading and thinking about the physics involved in the transportation of particles by the wind, and the landforms that result, this is probably one of the best, high density concentrations of the subject that I have found so far, and I don't think he managed to treat all of the variables. http://www.nps.gov/whsa/Sand%20Dune%20Geology.htm Defining the difference between dunes and ripples on Mars versus those on Earth is probably a bit more complicated, though.

> Oh, yes. I'm hoping they will kick that up to more like 75 meters/day, now that they've tested the waters.

Based on the tracking web info it looks like this was a "blind-drive" with slip-checking (driving in visodom mode) each 10m.
There seems to be no significant change on the ripples for the next 200m so it looks reasonable to think they will keep using this driving mode. At the end, it means the driving distance on a specific sol will just be limited by the *time* they allocate for driving.

Excellent.

Yes, excellent ddeerrff
And the difference between a micro-crater and a crater?

Edit : Do you have notice?

Sol 912 : http://origin.mars5.jpl.nasa.gov/gallery/a...00P1965L0M1.JPG
Sol 398 : http://origin.mars5.jpl.nasa.gov/gallery/a...00P1785L0M1.JPG

The size of the dune (riplles ) si the same.

Great article, one interesting point: "Rippling tends to develop on sandy surfaces that are in a state of relative equilibrium or slow deposition. Surfaces experiencing either marked erosion or vigorous deposition generally do not display rippling". ..which pretty much describes what we see on the plains, and predicts that the plains aren't being exhumed, at least recently, if the process indeed works similarly on Mars.

And maybe the large dunes at Meridiani are 'granule ripples' and therefore not as fossilized by the desert pavement or surface cohesion effects as we might think:
"...like ripples, granule ripples resulted from finer saltating grains pushing coarser grains (via surface creep) into jams. Unlike sand rippling, however, these concentrated ripples of coarser grains are rarely, if ever, moved by direct wind pressure. Consequently, they are more stable and can grow to larger dimensions than sand ripples. As more and more coarse grains arrive from upwind, the granule ripple can grow quite high and the resultant saltation shadow prevents movement of large grains from the crest into the leeside trough. In contrast to sand ripples, growth and movement of granule ripples is very slow, and individual granule ripples can exist for decades and even centuries, allowing for much greater heights and wavelengths than can develop on ephemeral sand ripples..."

it seems Meridiani has mostly Transverse dunes and Barchanoid ridges (looks like even some Reversing dunes around Beagle vicinity), but i havent noticed any plain Barchans sitting around, the article mentions "barchanoid types are associated with the least variability of wind direction" which agrees with the observation that Maridiani doesnt seem to get much directional wind variation. As for Star dunes, same rule applies, except for the wind eddies inside craters where the caustic-like ripple patterns in the basin of Endurance could be described as star-ripples.

...although other places on Mars, and not to get too off-topic here, would seem to suggest a star-dunes origin, notably, the star-like or dendrite-like features in the defrost regions near the poles (the ones that Arthur C. Clarke proclaimed, perhaps as a joke(?), were of biological origin). I had interpreted these features to probably be formed by progressive defrosting/expansion patterns in the soil, but now this possibility seems it might better explain it.

From the referenced site:



Which explains why I wasn't much luck finding in-depth dune resources. Good reference, thanks CR.

I was puzzled by the narrow ridge on the ripple/drift crest we've seen on the drifts iin this transitional zone, but according to McKee, this is called a "reversing dune" (figure 4). I'd suspect that variability in wind direction may be an orographic effect caused by the Victoria hill.

--Bill

We're burning aluminum now. Beagle Crater just vanished in a single sol.

I compared them tonight, and the size of the ripples here are similar to or smaller than those Opportunity was travelling over when it broke it's single sol and multisol distance records. I can't wait to see how far she went tosol.

atomoid: Great observations. When I studied aeolian transport and deposition many years ago, I was never exposed to many of those concepts, and thus had an oversimplified model in my mind for a long time. Following the rovers for these many years has forced me to reconsider some long-held beliefs. I am still learning, hopefully. I do know that many of the ripples found by both rovers have been described as armored (ie: covered with coarser grains). I think I remember some mention of granule ripples somewhere, perhaps observed by Spirit. But as for Meridiani ripples, it seems that every time the wheels have bit into them, finer material was present below the surface.

Bill: Thanks, and you're welcome. I also searched a long time for basic info without success. For some reason I must finally have used the right terms the other night. Still, one might wonder why "The single major work on sand dune formation" since 1941 hasn't been referenced more often if it was really so important. I know that sometimes happens. Anyway, I have to think there are more recent papers discussing other variables, but for the time being, I need to read that one again to fully digest it.

Yes this surface are as good as we ever might get. If I had been a mission planner (completely unthinkable that I ever would have been appointed but lets dream) I would even have suggested that the rover once again would do a few 'blind drives' again. Just aim over a stretch seen from the latest position that looks save and let the rover go.

We're not far from terrain that looks even better - i.e. free of any noticeable ripple all together. Perhaps 3 drives of 50-60m and we will be on stuff that is like the terrain we had between Eagle and Endurance. THAT - I would blind drive on...this stuff, I wouldn't be quite confidnent in it, I'd still want quite regular slip checks.

Doug

I'm not a fan of blind drives in the annulus quite yet -- yes, the surface looks good, and there look to be no problems with getting stuck in the ripples. But when I look carefully at the high-res versions of the cPROTO MOC image of Victoria and its surroundings, the annulus surface appears to have a lot of small dimples in it, arrayed in fracture lines that are somewhat reminiscent of Anatolia.

I'd hate to be barrelling along (well, as close to "barrelling" as Oppy or Spirit ever manage) on a blind drive that intersects a meter-deep dimple. Local slopes inside such features could be more than Oppy can manage, or worse, they may be full of soft, dark sand -- rover traps.

At the very least, I'd like to see one of these things close-up and make sure they're not hazardous before we set out on long, blind drives. It would be horrible to lose Oppy so close to Victoria because we got too cocky...

-the other Doug

This has been a slow-but-sure learning experience on aeolian processes. My education and professional experience haven't provided me with a great deal of background on sand, wind and dunes. There are many references on the Web, but one ends up looking at a lot of sources that aren't quite right and most Web searches end up in Frank Herbert's Dune corner. And learning a complex subject on your own leads to "TLAR Geomorphology", which may not always be correct (TLAR="That Looks About Right"). I'm glad to have Tim D. and Tim P. onboard.

I'm not a fan of barrelling, either. As other Doug points out, meter deep depressions mean half-meter deep loose sand and the risk is too gfreat. Remember what happened after Oppy left the smooth Endurance plain and got into the rippled transition to the etched terrain. Barrelling along at a record pace and *splat*.

Not to mention, we do need to stop and look at the ejecta material frequently. At least close Pancam L257, but possibly MI since Oppy unfurls the IDD nightly.

--Bill


PS-- here is an interesting MI of a drift surface I picked up today-- look at the granules and compare it to the other-Sol MIs (Sol 912 or so).

Can you show an example of these structures, pls?

I think these would be the same structures that are behind this current thread.

http://qt.exploratorium.edu/mars/opportuni...GTP1311R0M1.JPG

We can be at Victoria this weekend with that kind of driving! Let Oppy stretch her legs on this baby dune pavement towards victory!

Pedal to the metal!

She drove almost 71m tosol (info from the data tracking web).

6 of those puts us at the rim.

Doug

Here is the complete 360 degree panoramic view

from Sol 912 and Sol 913.

Taken with the Left navcam.

jvandriel

The longest drive since.... when?

Exactly; a bit more then 400m to the rim.
I guess they won't drive so aggressive once/if the terrain changes nearer to the rim and will "sniff" the ground before the last drives. We *may* be there at the rim in two weeks.

even with 50 m drives she'll make it in ca. 3 weeks. then its just a matter of carefully "sniffing" the final few meters for the rim. seems likely to occur sometime during the next shuttle mission STS-115 assuming on time lift-off on Aug 27.

Here's a polar view made from jvandriel's new pan.

Phil

Click to view attachment

QUOTE (Tesheiner @ Aug 20 2006, 05:07 PM)

Exactly; a bit more then 400m to the rim.
I guess they won't drive so aggressive once/if the terrain changes nearer to the rim and will "sniff" the ground before the last drives. We *may* be there at the rim in two weeks.

Two more weeks will be very close to sol 935
If I lose my bet because she get there before, I'll be very happy anyway.
It's so nice to see this rear cam view. Even if we don't know for sure what we'll find on the approch, I feel we're on "known" ground.

Here's an improved version of the equirectangular 902-903 pan, with Pancam images overlaid:



14000x7000 version

Did you ever try using "horizontal line" controls points on the horizon with the Panoramatools optimizer ?

Sol 914 equirectangular in progress:

Sol 914 Pancan drive-direction mosaic (L2):

A sol driving day up to 71 meters. That is a long for a Martian winter with less solar energy.

I am wondering about how much solar energy can Oppy spend per sol.

Trying to translate the 71 meters to how many minutes of driving:

If average speed:
71 meters --> 710 7100 cms / 2.5 cms/sec (avg speed) = 28400 2840 seconds/60 sec/min = 473 47.3 minutes --> 7:48 hour aprox

If maximum speed
5 cms/sec --> 23.7 minutes 3:24 hours of driving.

Still in doubt.

Rodolfo

Math recently corrected.
P.D.
I would rather not drive Oppy as blind except when Oppy goes back to Beagle Crater as I am certain about the surface and I can trust it fully. However, from Beagle to Victoria, better no to risk as I know that the sand surface has many tricks that the blind drive and sleepage aren't enough.

71m at 5cm/sec is 23.6 minutes, or 47.3 minutes @ 2.5cm/sec

Not sure what you're doing with the maths there.

Doug

I don't like the horizontal line tool DEC, usually if your FOV is correct and there have been added some control points near the horizon (manually if you have too), all should be fine. Some rotating and playing with the center point then (in the panorama editor) and you're there.

I've been writing some mini-tutorial regarding straight horizons using PTgui but need to finish it..I'll get to it one of these days I think

Now, back on topic, Victoria already rocks! Lookatthat sol 914 horizon Man this is going to be Soooo Sweeeeet ..

Nico

I saw the pancams from Sol 914......when Oppy gets to the rim THAT will be the "Hell of a View" point!

You could also use the next version of MMB, which will spit out a PTGui project file for you with all the camera pointings from the tracking database. Only works for Mars stuff though.

I'm not using control points at all. In fact if I add any control points, that seems to throw off the camera pointing info.

What an encouraging drive. Someone asked when was the last time Opportunity drove 70 meters. It has happened only once or twice since the right front wheel steering problems began. On sol 823 she drove 71.2 meters, and on sol 773 the maps show a drive that was very close to 70 meters, though I couldn't verify the distance in the updates archive at the MER site. They are surely not going to drive carelessly here, but the diminishing ripples should lead to longer drives. If the available power allows it, I can imagine seeing ~ 100 meter drives again.


Dilo: We were discussing the article linked to in message #152 in this thread. There are some examples in it.

Some tantalising details visible now...

VC on the horizon

Hmm... the more I look at that image the more I wonder if I should have been a farsider.

Scott

What a change in just two driving sols!
Simply compare the rim and craters details on tosol pancams and those from sol 909; beacon, Epsilon and other rim features right to the left of it, Hawking... All these features all visible on navcams too.



I got some info from the tracking web this evening (European time) to detail the driving; here you have it including some derived data (Dd, Dt, avg speed). The images are thumbnails (they are usually not downloaded at the exploratorium) from the navcam shots usually taken while driving in "visodom mode" (aka slip-checking).

QUOTE (Tesheiner @ Aug 20 2006, 11:05 PM)

What a change in just two driving sols!
Simply compare the rim and craters details on tosol pancams and those from sol 909; beacon, Epsilon and other rim features right to the left of it, Hawking... All these features all visible on navcams too.

This make me think that even if the view from the rim of VC will be spectacular, details some 750 m away on the other side of the bowl will be poorly defined. Good enough to go and reach for them

What a drive!

This is mhoward's pancam mosaic from 914 rather roughly turned into a polar. I might not have te angle right, it's just a guess. And oriented to show the approaching view, of course, not north-up.

Phil

Click to view attachment

Good to know about this new detail!

Now it is seen that the average speed is lower than 2.5 cms/sec nearing to 1.7 cms/sec. I think MER measure its speed by counting the revolutions of one of the six wheels or the average of six wheels along with the time. But, about the sleepage, how MER compares with the wheels revolutions (distance)? Let suppose that if MER has a neutral wheel (no traction), it would be able to measure exactly and be able to compare with motion wheels.

I suppose that sleepage computing is done in conjunction with the parallax of NAVCAM with the wheels revolutions?

Rodolfo

Which raises interesting questions about how the photo survey will be run. Getting a feel for what the whole of Victoria looks like may be much harder than with Endurance. What we can see from the rim won't tell us a lot about what the inside of the rim wall looks like. Which means we have to go in to see much of the layering.

It would be wonderful to circle the crater, then take a "victory(a) lap" around the inside!

You made my dream come true What is the average pixel error in the matching?

thanks

Nico

QUOTE (mhoward @ Aug 20 2006, 11:33 PM)

What a drive!

Oh Yes! You're even roving on the ceiling Mike

I really ought to get out in the garden and do some weeding, but you know how it is.

mhoward's full pan in polar format.

Phil

Click to view attachment

Wow, awsome image !

I'm not really sure - I think you only find that out when you create control points and optimize, which I'm not doing. But the stuff I'm currently posting is done using this technique, so you can judge visually.

The rim of Vicky is so irregular according to the orbital images that I think we'll actually get pretty good views from outside - if we can drive out onto the "promontories" we'll actually be quite close to the neighbouring inside cliffs, so we aren't restricted to imaging across the crater.

Then again, the slopes are so gentle here that they may decide to drive straight in!

The image with soft parallel ripples have induced me to recall one similar before when Oppy was stuck on Purgatory Sand. Now, I am trying to see further way onto VC, crossing diagonally the ripples. It seems that after a 50-80 meters there will be a change of surface morphology to more evenly flat. I think that on the way up to VC there will be small sinuous ripples, similar to when Oppy left Eagle crater toward to Endurance crater. The only tricks that I might anticipate are the ones with sapping kind surface (due to probably the gassing of CO2) or small depressions alike to Antonieta.

Again, the desert panorama view is harmonious for its uniformity of ripples.

Rodolfo