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Kilometers on the ground
tanjent
post Aug 1 2017, 01:53 AM
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Even if the slippage could be precisely accounted for, how could we settle on a definition of "distance traveled"?
It's like trying to compute the exact length of the coastline of France.
Any path with self-similar irregularities down to an infinitely small scale is not going to have a unique length unless you first specify the radius of measurement.

Ok, maybe a wheeled vehicle has a minimum turning radius, but in three dimensions the terrain will still cause infinitely small bumps that need to be factored in if you want the "exact" distance, and many of these will have occurred in between measurements. It will always be necessary to simplify the true path to a series of segments, and the distance between stopping points seems like the most expedient segment to use for most purposes.
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RoverDriver
post Aug 2 2017, 03:57 AM
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QUOTE (tanjent @ Jul 31 2017, 05:53 PM) *
.... and the distance between stopping points seems like the most expedient segment to use for most purposes.


I was not trying to be pedantic but really it all depends what you are trying to measure. For me it is mostly to measure the wear and tear on the vehicle, so to me discarding all twists and turns is definitely not the way to go. Only rarely we drive in a single straight line, most of the time we have two, three, even five segments with large turn in place (every 90 deg turn in place corresponds to about 5m of wheel motion!). Since we have been trying to reduce wear and tear on the wheels drive paths have been quite tortuous and I would not be surprised to find out that just connecting the end of drive coordinates would underestimate by more than 30%.

Paolo

PS: I finally ran some numbers. Missionwide, the difference between reported odometry (*) and straight line distance between start and end of drive on average is 35.5%.
(*) reported odometer: odometer as reported by the vehicle.


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Disclaimer: all opinions, ideas and information included here are my own,and should not be intended to represent opinion or policy of my employer.
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Glevesque
post Aug 2 2017, 01:00 PM
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QUOTE (RoverDriver @ Aug 1 2017, 10:57 PM) *
I was not trying to be pedantic but really it all depends what you are trying to measure. For me it is mostly to measure the wear and tear on the vehicle, so to me discarding all twists and turns is definitely not the way to go. Only rarely we drive in a single straight line, most of the time we have two, three, even five segments with large turn in place (every 90 deg turn in place corresponds to about 5m of wheel motion!). Since we have been trying to reduce wear and tear on the wheels drive paths have been quite tortuous and I would not be surprised to find out that just connecting the end of drive coordinates would underestimate by more than 30%.

Paolo


I apologize in advance for having very poorly expressed myself in my previous positions, and I greatly thank all those who participated in this discussion, as well as providing valuable assistance that gave a better understanding of the challenges of Driving the rover on Mars. Indeed, I understand the dilemma of driving the rover facing the premature wear of its wheels. And this is of utmost importance to potentiate a longer mission of Curiosity on Mars. In fact, my question was just to know where I could find reliable data to reproduce on a mileage map traveled according to the trajectory, the answer that my nogal given is greatly satisfactory on this. If I asked this question, it is because the three sources that serve as my reference have different data on daily distances traveled, and I wanted to understand where this difference comes from.

I thank you all.
______________________________________________________________________

Je m'excuse d'avance de m'avoir très mal exprimé dans mes postes précédant, et je remercie grandement tout ceux qui ont participé à cette discussion, tout en y apportant une aide précieuse qui a donnée une meilleurs compréhension sur les défis de la conduite du rover sur Mars. Effectivement, je comprend bien le dilemme sur la conduite du rover faisant face à l’usure prématurée de ses roues. Et cela est d'une très grande importance pour potentialiser une plus longue mission de Curiosity sur Mars. En fait, ma question était juste de savoir ou je pouvais trouver des données fiables pour reproduire sur une carte de kilométrage parcourus en fonction de la trajectoire, la réponse que ma donné nogal est grandement satisfaisante à ce propos. Si j'ai posé cette question, c'est que les trois sources qui me sert de référence ont des données différentes sur les distances journalière parcourus, et je voulais comprendre d’où viens cette différence.

Je vous remercie tous.
______________________________________________________________________

Exemple with Sol 967 :

1- Midnight Planets : http://www.midnightplanets.com/web/MSL/sol/00967.html
2- Curiosity Drive Log : http://www.curiositymsl.com/tracking/drivelog.html
3- Curiosity Rover's Location/JPL-Nasa : https://mars.jpl.nasa.gov/multimedia/images/?ImageID=7148



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Glevesque
post Aug 2 2017, 07:15 PM
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I would also like your help to trace the daily cumulative distances (per Sol) that were greater than one hundred meters. Here is the list that I was able to come out on this subject:

PS: I did not find the distance record assuming the Sol 976 of 262.41 meters (May 2015)
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J'aimerais également votre aide pour retracer les distances cumulatifs journalière (par Sol) qui ont été supérieurs au cent mètres. Voici la liste que j'ai pu resortir a ce sujet :

PS : Je n'ai pas retrouver le supposer record de distance au Sol 976 de 262.41 meters (mai 2015)
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Curiosity Rover's Location (Nasa/JPL)
Analyst's Notebook entry for Sols
---------------------------------------------------
Sol - Dist(m) - Earth Date - Information sources
385 - 128.81 - 06/11/2013 - https://mars.nasa.gov/multimedia/images/?ImageID=5549
419 - 117.84 - 11/10/2013 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=5649
657 - 112.63 - 12/06/2014 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=6319
661 - 109.35 - 16/06/2014 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=6342
662 - 123.88 - 17/06/2014 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=6344
665 - 121.60 - 20/06/2014 - https://mars.nasa.gov/multimedia/images/?ImageID=6350
668 - 104,85 - 23/06/2014 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=6366
671 - 113.58 - 26/06/2014 - https://mars.jpl.nasa.gov/multimedia/images/?ImageID=6372

Source : https://an.rsl.wustl.edu/msl/mslbrowser/tab.aspx?t=MP


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RoverDriver
post Aug 2 2017, 10:43 PM
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QUOTE (Glevesque @ Aug 2 2017, 12:15 PM) *
I would also like your help to trace the daily cumulative distances (per Sol) that were greater than one hundred meters. Here is the list that I was able to come out on this subject:

PS: I did not find the distance record assuming the Sol 976 of 262.41 meters (May 2015)
...


Sol 00976 was 74.33 meters.

Here's the list of 100+ meters drives.

00548 100.06 meters
00547 100.26 meters
00340 100.27 meters
00960 102.35 meters
00569 102.95 meters
00454 103.33 meters
00644 104.24 meters
00668 105.24 meters
00670 107.15 meters
00371 110.15 meters
00751 114.32 meters
00671 116.79 meters
00657 120.96 meters
00419 125.79 meters
00662 132.95 meters
00661 137.57 meters
00385 141.49 meters
00665 143.64 meters

The distance record still is held by Oppy with 219 meters on Sol 410.

Paolo


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Glevesque
post Aug 4 2017, 04:55 AM
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A big thank you for sharing his information.
------------------------------------------------

Un grand merci pour le partage de ses informations.




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nogal
post Aug 17 2017, 06:11 PM
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Hello again,

The discussion is this thread prompted me to thoroughly review the km and mile signposts in "The Martian Way" kml file, especially at the light of new (to me) information in the articles by Vasavada, A. R., et al. and Rice, M. S., et al. which provide sub-meter accuracy for the total traversed distance for sols 0-494 and 535-634, respectively. The former allows very precise location determination of kms 0 through 4 and miles 1 and 2; the latter extends this to kms 5 and 6 and miles 3 and 4.

Additionally, starting with sol 1282, the description on NASA/JPL Location and Traverse maps ("Where is Curiosity") includes the total traversed distance to an accuracy of 10m. In this way good estimates for kms 13 to 17 and miles 8 to 10 can be made.

Km 10 was abundantly mentioned. Thus I "only" needed to "guesstimate" the locations of kms 7, 8, 9,11, and 12, and miles 5, 6, and 7. This proved to take a lot longer than I antecipated, which explains why I have not made any recent updates to Curiosity's GE path. Phil Stooke's maps have several of the guessed kms, which is good corroboration - thank you Phil. Despite doing my very best, errors may exist. I have after all, "guesstimated" several locations. I would be very thankful for any information that could improve the accuracy of those locations.

In short, here is the revised list of kms and sols:
1 335
2 365
3 404
4 436
5 540
6 587
7 655
8 670
9 743
10 957
11 1098
12 1248
13 1376
14 1448
15 1526
16 1666
17 1754

And here is the complete list, with information sources. To use it, dowload it and drop the ".txt" from its name.
Attached File  MSL_kms.csv.txt ( 129.33K ) Number of downloads: 108


Fernando

Edit: Something I've learned: in the Analyst's Notebook odometry or total odometry is not equivalent to traversed distance. The former really does exceed the latter.
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