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Tom Tamlyn
Three years ago RoverDriver posted a request that the forum's members pool their talents and experience with Martian images to analyze the drivability of the terrain between Victoria and Ithaca Endeavour. The result was an explosion of collaborative work that made compelling reading, even for members like me, who hardly understand the first thing about the techniques involved and have trouble manipulating, let alone understanding, the graphic work products.

About a month later JPL asked Paolo to discontinue his own involvement. Despite this disappointing (albeit understandable) development, the work continued for nearly another year.

I'd like to know if any of the participants has had the occasion to review his work in light of the photographic record of Opportunity's actual route (or of subsequent MRO imaging) and is willing to share his thoughts about how the analysis compares with what we have learned since the work was done.

TTT
Tom Tamlyn
In light of a private message I've received from a respected member of the forum, I want to make it clear that my question was directed to those members who contributed to the drivability analysis who are not professionally involved with the Rover missions, who might be interested in comparing their prior work to what subsequent rover imagery has revealed.

TTT
jamescanvin
I haven't done any detailed analysis of how well my drivability maps turned out but it didn't seem to far off smile.gif

I did plenty of eyeballing of HiRISE images coloured with derived ripple size at the time to know that was working well and we now have plenty of experience comparing ripples from the ground with HiRISE to know how those compare so I'm not surprised it worked fairly well.
Floyd
Tom, thanks for pointing us back to this great thread. I spent over an hour last night viewing comments and maps. The excitement and responses to Paolo's challenge were one of the most fantastic seen on this forum. Paolo, I thank you for all you contributed in you brief time on this forum and even more for your ongoing efforts as an RP extraordinaire.
Tom Tamlyn
I apologize for this late response. A lingering health issue (not really serious, just debilitating and annoying) limited my energy and thus activities for a while, but I'm getting better.

Thanks to Floyd and James for their interesting replies.
RoverDriver
QUOTE (Floyd @ Sep 6 2011, 09:02 AM) *
Tom, thanks for pointing us back to this great thread. I spent over an hour last night viewing comments and maps. The excitement and responses to Paolo's challenge were one of the most fantastic seen on this forum. Paolo, I thank you for all you contributed in you brief time on this forum and even more for your ongoing efforts as an RP extraordinaire.


I apologize for not seeing any of this. For several reasons I was away from UMSF for a few years. I eventually had to do traversability analysis for real but for another mission (MSL). It has been a monumental job that took almost three years and the help from many talented people. We'll see how it compares with the real Gale.

I'm glad my challenge kept UMSF'ers busy. What I was trying to do back then was to give you a glimpse in what it takes to work in a real space exploration program. I hope you enjoyed it as much as I enjoyed interacting with all of you. Thank you, it has been a real treat for me.

Paolo
MahFL
So, Paolo, how does the terrain look for driving in Gale crater ?
RoverDriver
QUOTE (MahFL @ Jul 3 2012, 03:06 AM) *
So, Paolo, how does the terrain look for driving in Gale crater ?


Mostly benign, the plains near Mt Sharp (or Palus, whatever it is called) are pretty flat, good driving terrain, there are lots of small mesas with scarps we probably want to avoid. There are some rocks, but not as rocky as Eberswalde would have been. Once we get to the mound where the clays are, we should be able to climb up following a few "narrow" valleys. There the terrain is steeper, with some dunes going across these valleys and scree near the base of the steeper faces. This will present some challenges for driving but I can't wait to try.

I assume all of you have seen you can download all of the HiRISE images at Gale, including all the DTMs (http://hirise.lpl.arizona.edu/dtm/). Compute the slopes from the DTMs and apply a slope threshold similar to what MER can climb and you get a rough idea of where we can go.

There is a long paper on MSL landing site selection that is being published that includes besides all the scientific selection criteria, details of how I have done the traversability analysis: Golombek, M., et al., 2012, Selection of the Mars Science Laboratory landing site: Space Science Reviews, in press, June 2011.

Paolo
MahFL
Could someone create a slope map please, I don't know how to do that.
RoverDriver
QUOTE (MahFL @ Jul 3 2012, 05:10 AM) *
Could someone create a slope map please, I don't know how to do that.


MahFL, the map I have is 5.2 GB and can't release it, of course. What tools do you have? I can definitely show you how to compute it. There are various techniques that can be used, the way *I* decided to compute it is to compute the slope as the gradient of the elevation map. I compute the slope in the East-West direction: slopeEW = atan(deltaZ/deltaEW), that is, I compute the difference in Z between the pixel where the rover is and the neighboring pixels in the East and West direction divided by the horizontal distance between the pixel where the rover is the neighboring pixel under consideration. I repeat the process in the North-South direction: slopeNS = atan(deltaZ/deltaNS), using a similar computation as above. I finally compute the slope magnitude as the square root of the sum of the squares slope=sqrt(slopeEW^2 + slopeNS^2) and the slope direction as the arctangent between the two components. The DTMs posted on the HiRISE web site are in PDS format I think. If you can't read those, you can sort of cheat and get the number of rows and columns from the header (it is in ASCII), compute the array size as rows*cols*4 (it is a 4 bytes floating point array), skip the header whose size in bytes is filesize - rows*cols*4 and then start reading the array as floating point numbers in row major order. I can already see many people already using emacs and gcc coding their way up to Mt Sharp ;-)

Paolo
MahFL
Now I feel guilty you posted such a long reply. I'm NOT one of the people on UMSF that creates images, I just enthusiastically view them. blink.gif
RoverDriver
QUOTE (MahFL @ Jul 3 2012, 08:39 AM) *
Now I feel guilty you posted such a long reply. I'm NOT one of the people on UMSF that creates images, I just enthusiastically view them. blink.gif


I'm sure someone will compute these maps and post them. I wish I could post mine. Some of the traversability maps are included in the paper I cited above.

Paolo
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