IPB

Welcome Guest ( Log In | Register )

41 Pages V  « < 22 23 24 25 26 > »   
Reply to this topicStart new topic
Winter Quarters, at Low Ridge Haven
Shaka
post Jun 4 2006, 02:13 AM
Post #346


Senior Member
****

Group: Members
Posts: 1229
Joined: 24-December 05
From: The blue one in between the yellow and red ones.
Member No.: 618



Works for me. Sunset and Lonesome Hill. Be nice to see realistic color.
Astro0 could do a "Spirit rides into the Sunset" composite.
So could you, I'll wager.


--------------------
My Grandpa goes to Mars every day and all I get are these lousy T-shirts!
Go to the top of the page
 
+Quote Post
Airbag
post Jun 4 2006, 02:25 AM
Post #347


Member
***

Group: Members
Posts: 402
Joined: 3-August 05
Member No.: 453



QUOTE (helvick @ Jun 3 2006, 04:15 AM) *
The JPL update confirmed James' third alternative. The precision of the knowledge of the orientation of the rover was improved because they had many more sun pointing shots over time with which to refine the calculation.


This issue is perhaps not as straighforward as it might seem - at least to me. Those Sun images are roughly 20 pixels across, and let's assume the centroid can be measured to within 1 pixel. Since the Sun's angular diameter as seen from Mars is about .35 degrees, the position of the Sun can in theory be measured to within say .015 degrees. This is of course assuming the rover's position is know (it is), and the rovers's clock and Pancam pointing accuracy are at least as good as the measurements require.

Then, a series of measurement with the Sun near the zenith (to avoid refractive effects, which can't be that big a deal on Mars anyway) can be used to obtain the rover's pitch and roll, assuming a reasonable knowledge of its yaw. Yaw can not easily be measured this way - think of it this way, the Sun at zenith would look the same for all yaw values (assuming a level rover). Towards sunset a similar set of measurements can be used to refine yaw as even refractive effects would not affect the "sideways" position of the Sun is the sky. These new measurements would then be fed into the next cycle.

Given the in theory very accurate measurements of the Sun's centroid, I presume then that it is a greater inaccuracy of the rover's clock and/or Pancam pointing accuracy that limits the rover's attitude accuracy and hence benefits from averaging over multiple solls?

Well, a fascinating topic I think, and I'd be interested to learn more if anybody has any more information (as opposed to my speculation blink.gif )

Airbag.
Go to the top of the page
 
+Quote Post
helvick
post Jun 4 2006, 11:05 AM
Post #348


Dublin Correspondent
****

Group: Admin
Posts: 1792
Joined: 28-March 05
From: Celbridge, Ireland
Member No.: 220



QUOTE (Airbag @ Jun 4 2006, 03:25 AM) *
Then, a series of measurement with the Sun near the zenith (to avoid refractive effects, which can't be that big a deal on Mars anyway) can be used to obtain the rover's pitch and roll, assuming a reasonable knowledge of its yaw. Yaw can not easily be measured this way - think of it this way, the Sun at zenith would look the same for all yaw values (assuming a level rover).
Airbag.

True but:
A: The rover is not level.
B: The sun shots are taken at a variety of times of day not just one.
C: In this case we have sun shots taken over an extended period of time and the suns overall track has changed significantly (at least relative to the accuracy of the Pancam).

Its a very interesting topic all the same.
Go to the top of the page
 
+Quote Post
Airbag
post Jun 4 2006, 02:04 PM
Post #349


Member
***

Group: Members
Posts: 402
Joined: 3-August 05
Member No.: 453



QUOTE (helvick @ Jun 4 2006, 07:05 AM) *
True but:
A: The rover is not level.
B: The sun shots are taken at a variety of times of day not just one.
C: In this case we have sun shots taken over an extended period of time and the suns overall track has changed significantly (at least relative to the accuracy of the Pancam).

Its a very interesting topic all the same.


Some thoughts on your comments:

A: For the purposes of these hand waving arguments, I'd say 11 degrees is effectively level (as compared to the 90 degrees zenith angle).

B: I suggested two sets of measurements should be sufficient. Looking at the positions of the Sun shots (using MMB's pano mode for sols 807-855), it appears the measurements fall into two clusters - one near the zenith, and the other about 20-30 degrees above the horizon, with some outliers in between.

C: This I believe is at the heart of the issue, assuming the Pancam pointing knowledge is indeed less than the Sun's measured accuracy (in pixels). This link states the pointing knowledge is 0.1 degrees, which although about a magnitude larger than my centroid accuracy estimates above, is still much less than the almost 2 degrees attitude adjustment. So I'm still puzzled why the adjustment was so large.

Airbag
Go to the top of the page
 
+Quote Post
helvick
post Jun 4 2006, 02:49 PM
Post #350


Dublin Correspondent
****

Group: Admin
Posts: 1792
Joined: 28-March 05
From: Celbridge, Ireland
Member No.: 220



QUOTE (Airbag @ Jun 4 2006, 03:04 PM) *
C: This I believe is at the heart of the issue, assuming the Pancam pointing knowledge is indeed less than the Sun's measured accuracy (in pixels). This link states the pointing knowledge is 0.1 degrees, which although about a magnitude larger than my centroid accuracy estimates above, is still much less than the almost 2 degrees attitude adjustment. So I'm still puzzled why the adjustment was so large.

Here's a useful link
If I'm reading this correctly then in general 2 degree overall pointing was deemed sufficient as that is the accuracy required for ensuring that they HGA can be pointed at Earth so that the procedures used to refine the accuracy of the attitude could terminate as soon as the error was within that limit even though they have the capacity to be more accurate than that. One point that you made already that is probably worth investigating further is whether the clock timing accuracy (and whatever overall positional uncertainty there is for the location of the rover) could contribute to the error.

I'm still trying to find a paper that I read at some point last year that explained the attitude calculation and sun shot processes in even more detail than the one above, I'll post a link if I track it down.
Go to the top of the page
 
+Quote Post
Airbag
post Jun 4 2006, 05:23 PM
Post #351


Member
***

Group: Members
Posts: 402
Joined: 3-August 05
Member No.: 453



QUOTE (helvick @ Jun 4 2006, 10:49 AM) *


Ah, thanks for that link - it made for fascinating reading. I guess it is the 'Sungaze" mode were were talking about then. I agree, it seems that HGA pointing needs drove the 2 degrees "is good enough" model. One of the sections mentioned that the attitude calculations go on until the "covariances converge to the 1.5 degree level"; presumably that means when subsequent estimates agree to within some function of pitch, yaw and roll that results in a delta of less than 1.5 degrees.

BTW, did you see that mention of in theory being able to use the gyros as a gyrocompass to detect heading, if only the software supported it? (as a fallback if the Pancam was no longer working).

It must have been very satisfying to have worked on this attitude/postion software and see such great results.

Airbag
Go to the top of the page
 
+Quote Post
hortonheardawho
post Jun 4 2006, 09:57 PM
Post #352


Member
***

Group: Members
Posts: 133
Joined: 3-June 06
From: the jungle of Nool
Member No.: 799



1/2 size Preliminary Left eye McMurdo panorama:



everything from L2/L7 to L2...L7 images with lots of synthesized missing data rectangles.

No attempt to match contrast / brightness / color between images except what Autostitch provides.

Color by Horticolor:

Do not look upon me; Lest with this piteous action you convert
my stern effects: then what I have to do will want true colour;
tears perchance for blood.
Go to the top of the page
 
+Quote Post
helvick
post Jun 4 2006, 10:13 PM
Post #353


Dublin Correspondent
****

Group: Admin
Posts: 1792
Joined: 28-March 05
From: Celbridge, Ireland
Member No.: 220



QUOTE (Airbag @ Jun 4 2006, 06:23 PM) *
BTW, did you see that mention of in theory being able to use the gyros as a gyrocompass to detect heading, if only the software supported it? (as a fallback if the Pancam was no longer working).

Yeah - it's a very neat set up - it's pretty impressive that you can have a solidstate closed unit that can give you a decent compas (and general attitude) bearing solely from the motion of the planetary surface you happen to be perched on.
QUOTE (Airbag @ Jun 4 2006, 06:23 PM) *
It must have been very satisfying to have worked on this attitude/postion software and see such great results.

Personally I'd have said that about almost any part of these magnificent machines but this is one of the very impressive parts.
Go to the top of the page
 
+Quote Post
Astro0
post Jun 5 2006, 05:58 AM
Post #354


Senior Member
****

Group: Admin
Posts: 2700
Joined: 21-December 05
From: Canberra, Australia
Member No.: 615



QUOTE (Shaka @ Jun 4 2006, 12:13 PM) *
Works for me. Sunset and Lonesome Hill. Be nice to see realistic color.
Astro0 could do a "Spirit rides into the Sunset" composite.
So could you, I'll wager.


Attached Image
File:151k
A very quick version from your suggestion Shaka.
Might be nice to do this in much higher resolution as better calibrated versions become available later.
Cheers
Astro0
Go to the top of the page
 
+Quote Post
Tesheiner
post Jun 5 2006, 07:37 AM
Post #355


Senior Member
****

Group: Moderator
Posts: 4269
Joined: 19-April 05
From: .br at .es
Member No.: 253



QUOTE (hortonheardawho @ Jun 4 2006, 11:57 PM) *
1/2 size Preliminary Left eye McMurdo panorama:


Beautiful, as usual!

PS: I wasn't aware you were using autostitch. Just in case, there is a thread with some tips on this nice tool.
Go to the top of the page
 
+Quote Post
Ant103
post Jun 5 2006, 09:10 AM
Post #356


Senior Member
****

Group: Members
Posts: 1317
Joined: 12-February 06
From: Dijon - FR
Member No.: 678



Hello,

Very nice AstroO, but, I think you should darken the pancam.

Also, here is my own version of the McMurdo pan, only the images taken toward horizon. I reserved an other treatment to the rest of the pan.



--------------------
Go to the top of the page
 
+Quote Post
mhoward
post Jun 5 2006, 03:52 PM
Post #357


Senior Member
****

Group: Moderator
Posts: 3385
Joined: 11-August 04
From: USA
Member No.: 98



Welcome, Horton!

Here is a combined Autostitch/MMBview version of the Spirit Sol 855 Navcam pan. It looks a bit odd, but the advantage is that the horizon is properly levelled. I couldn't for the life of me get Autostitch by itself to level it properly.

Go to the top of the page
 
+Quote Post
hortonheardawho
post Jun 5 2006, 06:44 PM
Post #358


Member
***

Group: Members
Posts: 133
Joined: 3-June 06
From: the jungle of Nool
Member No.: 799



QUOTE (mhoward @ Jun 5 2006, 11:52 AM) *
Welcome, Horton!

Here is a combined Autostitch/MMBview version of the Spirit Sol 855 Navcam pan. It looks a bit odd, but the advantage is that the horizon is properly levelled. I couldn't for the life of me get Autostitch by itself to level it properly.


Er, thanks mhoward.

I think autostitch must weight each join match equally -- so the near point errors introduced by non-panoramic images cause uncorrectable distortions in the panorama. A better scheme would be to weight points near the top of the panorama more heavily. Perhaps a user option parameter? 100 to -100? ( top to bottom weighting ?)

I think that I will end up using PT Assembler for the "final" product.

For those not aware, the rover camera images are NOT proper panorama images: The cameras do not pivot through the optical axis of the camera.

For people interested in real panoramas with a lot of depth this is an important factor.

Also also a uniform exposure and white balance is critical to a totally successful panorama. Again lacking in the rover images.

But we do what we gott'a do and work with what we have.

We go to the computer with the images we have and not the images we would like.
Go to the top of the page
 
+Quote Post
fredk
post Jun 5 2006, 07:35 PM
Post #359


Senior Member
****

Group: Members
Posts: 3029
Joined: 17-January 05
Member No.: 152



Can anyone suggest what Spirit's up to with this curious navcam series?
Go to the top of the page
 
+Quote Post
jamescanvin
post Jun 5 2006, 10:40 PM
Post #360


Senior Member
****

Group: Moderator
Posts: 2154
Joined: 9-February 04
From: UK
Member No.: 16



QUOTE (fredk @ Jun 6 2006, 05:35 AM) *
Can anyone suggest what Spirit's up to with this curious navcam series?


CODE
860 p0060.01 40  40  0   0   0   80   photon_transfer_left_navcam
860 p0061.01 40  40  0   0   0   80   photon_transfer_right_navcam


--------------------
Go to the top of the page
 
+Quote Post

41 Pages V  « < 22 23 24 25 26 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 24th April 2014 - 11:59 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.