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Distant vistas, Endeavour, Iazu, and beyond
ngunn
post Mar 15 2010, 08:10 PM
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OK so we have two horizon features. Tim's '181' and the one about 15 degrees to the right of it as seen from here. Probably both are further away than the twins, which may not break the horizon although they should lie close to the 181 azimuth of the leftmost horizon feature. Would that be a fair assessment? Phil's earlier identification of the rightmost of the pair probably depended on your earlier ID of the twins, fredk, so it seems to me that both of the horizon features now still await secure identification on the map. Here are links to the two images in which they appear, a little right of centre in both cases:
http://qt.exploratorium.edu/mars/opportuni...00P2391L6M1.JPG
http://qt.exploratorium.edu/mars/opportuni...00P2391L6M1.JPG
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Stu
post Mar 15 2010, 08:57 PM
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No Dougal, those hills are far, far away... wink.gif

Wow, just noticed today marks the 6th anniversary of me joining the forum... Thanks to everyone who makes it such a great place to hang out and, of course, thanks to Doug for starting it in the first place. smile.gif


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Geert
post Mar 15 2010, 10:32 PM
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Given the fact that the rover positions are quite accurately known, if the same features turn up in images taken at different sols (different positions), wouldn't it be possible to triangulate the features on the map?
The distance between the L/R pancam/navcam is way too short for accurate measurements over such distances, but if you have images/measurements taken at different positions, you might have a baseline which is long enough to get a good enough fix on the positions of these features.

I don't know whether there is accurate azimuth bearing information for the images (relative to true north, iso relative to rover) or if you can derive it from the relative camera bearing and the rover bearing itself, but otherwise, once you have clearly identified one feature you should be able to get the bearing of every other feature by counting pixels (given that the camera field of view is known).
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fredk
post Mar 15 2010, 11:00 PM
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Yeah, that's more or less what I did when I concluded the original ID's were wrong. We should've seen much more parallax shift between the features. But that was a relative argument. I guess what you're saying is if we have absolute azimuths for each image, we can work out distances for features, if they're not too much farther away than our baseline, and if errors in the absolute azimuths don't dominate.
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Geert
post Mar 16 2010, 03:28 AM
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QUOTE (fredk @ Mar 16 2010, 07:00 AM) *
I guess what you're saying is if we have absolute azimuths for each image, we can work out distances for features, if they're not too much farther away than our baseline, and if errors in the absolute azimuths don't dominate.


Yep, if you have absolute azimuths for each feature, you can work out the exact position (lat/lon) of each feature. Accuracy will depend on the length of your baseline (distance between positions/images) and the accuracy of your azimuth. The more different bearings (different images/azimuths) you get, the more accurate your positionplot also.

But even if you do not have absolute azimuths you could probably work out locations if you have two known and one unknown feature, just by measuring the number of pixels (along the horizon) between the features. Given a known baseline (distance between the two positions where the images were taken) and known positions, you can work out the true position of object number 3 (compared to known objects 1 and 2) if you measure the angle (count pixels) between objects 1-2, 2-3, and 1-3 in both images. I would have to work through some of the books again, but it should be possible.
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ngunn
post Mar 16 2010, 10:10 AM
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I've noticed something, in fact two things, in today's images. They're so faint that they may not be real at all but they're in both the L and R views. Looking back I now think I can see them in yesterday's images too. They are a couple of bumps on the horizon about 2 degrees and 3.5 degrees to the left of the dark horizon feature here:
http://qt.exploratorium.edu/mars/opportuni...FNP2392L6M1.JPG

I'll try to post annotated images but with my primitive IT skills that won't be quick.

Edit: The left of the two is directly above a nearer dark dune.
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ngunn
post Mar 16 2010, 10:25 AM
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Attached (hopefully)
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Attached File  Faint_bumps_on_the_southern_horizon_16_Mar_2010.doc ( 71.5K ) Number of downloads: 139
 
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ngunn
post Mar 16 2010, 10:51 AM
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And from yesterday:
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Attached File  Faint_bumps_on_the_southern_horizon_15_Mar_2010.doc ( 56.5K ) Number of downloads: 80
 
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ngunn
post Mar 16 2010, 11:53 AM
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Possible ID?

Oops arrows missing, trying again.
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Attached File  Possible_identification_of_southern_hills.doc ( 35K ) Number of downloads: 159
 
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jamescanvin
post Mar 16 2010, 12:58 PM
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QUOTE (ngunn @ Mar 16 2010, 11:53 AM) *
Possible ID?


I don't have a change to check the ID but a couple of weeks ago I was actually looking for features in the pancams to match the ID you point to, thinking that there was a chance they might visible. I couldn't spot anything then, but hopefully the clearing atmosphere has changed that.

The feature is actually part of the rim of the gigantic Miyamoto Crater, whose name will be familiar to may here as one of the rejected MSL landing sites. Although that particular feature is actually much closer (just outside the landing ellipse in fact) of another rejected MSL site 'South Meridiani'


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ngunn
post Mar 16 2010, 01:46 PM
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QUOTE (jamescanvin @ Mar 16 2010, 12:58 PM) *
Miyamoto Crater


Cue a much nicer context image (though I notice the colouring is a bit mis-registered with the topography):
http://mars8.jpl.nasa.gov/msl/news/images/...to_ellipse2.jpg

BTW you don't say if you see real features where my arrows point in the pancams. I'm still waiting for confirmation that they're really hills and not something I should see a doctor about.
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fredk
post Mar 16 2010, 02:57 PM
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I agree there are two very faint features on the horizon to the left of the most prominent dark feature. They are visible in both 2181 and 2183 images. I don't have the software to view your identification files, but my guess is that these features might be the "south hill" features we've been looking for for some time, at about the same distance as Bopolu. Nice catch!
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Bill Harris
post Mar 16 2010, 03:45 PM
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I'm not worrying about the distant-distant features for right now. We'll be at Twin Craters in a week or so, a bit closer to where the slope breaks and with one less intervening feature. Meanwhile, I'm going to be looking at the sand and rock under our wheels and on the lookout for changes afoot.

--Bill


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ngunn
post Mar 16 2010, 04:11 PM
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QUOTE (fredk @ Mar 16 2010, 02:57 PM) *
I don't have the software to view your identification files


Its only a word document with arrows on it. unsure.gif

Anyhow at first I thought it could be those outlying hills at Bopolu distance, but I thought these blips were too close together and a bit too far to the right for that, so I plumped for a couple of higher peaks farther away on the Miyamoto rim. Highly speculative at this stage but I'm sure James will nail it for us (and maybe the nearer features at the same time).
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Bill Harris
post Mar 16 2010, 05:28 PM
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OK, I got to fiddling around with those Pancams from today-- 1P321987621EFFACFNP2392R1M1 and the next one. Cropped, stretched, pasted and enhanced, the panorama ain't pretty, but it does show what ngunn and Fred note. The nearby dark horizon feature, Twin Craters, on a slight rise on the left which drops off to the right, showing a more distant horizon behind the rise. On this horizon is another crater on the right, with a pair of faint hills to the left of it.

Rather like Russian nested-dolls, no?

--Bill
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