# Were the distances traversed by Perseverance on Sol 718 and 719 each exactly 415.27 m or were they added together 415.27 m and if so, why?

The image above is an annotated screenshot of a part of the Perseverance location map.
On the location map the white line represents the trajectory that Perseverance has traveled in Jezero crater. When you place your cursor on a white dot you get the sol number, when you place it on the white line between the dots, you get the distance traveled by the rover between the dots.
On the image above, I've placed the sol numbers and the distances between those sol numbers along Perseverance's trajectory.
It's easy to see that the white line between Sol 716 and 717 has about the same length as the white line between Sol 717 and 718, while the distances of 216.52 m and 415.27 m traveled along those lines that are showed on the location map differ so much.

Also, the fact that 2 distances would have exactly the same length of 415.27 m seems very unlikely.

A likely explanation could be that the distances traversed on Sol 718 and 719 were added together, the sum being the 415.27 m.

Could there be a special reason for this, like Perseverance traveling from Sol 717 to Sol 719 without recharging on Sol 718 ?
Or did Perseverance drive perhaps autonomously all the time on the two consecutive days ?

• Martian traffic police aren’t going to be happy if it was driving around in twilight without headlights… Mar 4 at 16:56
• It will be much, much easier for some (like me) to understand if you can make a small table with the data your describing, instead of just describing the tabular data in prose, and replace things like "last but three" with the actual sol numbers for the mission.
– uhoh
Mar 5 at 1:05
• @uhoh I've made another edit, I think the question should be easier to understand now. Mar 5 at 13:05
• Still not really fixed @Cornelis Mar 5 at 13:33
• New Feature: Table Support
– uhoh
Mar 5 at 22:09

Partial answer: I don't believe this was a continuous drive, because NavCam images are provided for the end of the Sol 718 drive. Paul Hammond, one of the community contributors on r/PerseveranceRover (who also shows up later in the Mastodon links), has shared a lot of links to the raw data, and also processed JSON data (see image 10) showing the 415.27m data on Sol 719, with an indication that it's the record drive length.

I asked Mastodon user 65dBnoise about this; their response is that Sol 718 was added to the map later, was a stop, but the stop apparently was not considered for the drive length and the actual drive lengths should be 199m between Sol 717 and 718 and 216m between Sol 718 and 719 (rounded to the nearest meter).

Sol 718, RMC 34.3196, is missing for some reason from #NASA's map, but there was a late afternoon stop there and the drive resumed the next sol. The missing Sol may lead to miscalculations.

I also asked Paul Hammond, who replied that it may be a result of a single drive command that then took multiple Sols, with the explicit instructions

Now mouse-click the white traverse line anywhere between those waypoint markers, and the track colour changes to yellow, and you see that it's actually one commanded drive that took place over two sols IMAGE and not 2 drives each of 415.27 meters.

...

So I believe the map is 100% correct, but there is a distance error in the GeoJSON and JSON data for drive on 718 (I think that should possibly have a dist_m value of 0).

Note that these aren't official sources, but I'm inclined to trust them because they have been paying continuous attention to the rover data.

I've also found out about some JSON sources for Perseverance but they don't seem to contain the same data, esp. not the drive distance. Emily Lakdawalla posted an explainer for that JSON set, which contains this (emphasis hers):

Site increments whenever the rover updates its knowledge of its orientation by taking a photo of the Sun to note its position in the sky. Whenever site increments, drive gets reset to zero

Maybe that's related? "Drive" isn't an odometer, it's a start/stop counter, but if other "rover motion counters" also reset when site increments, and site didn't increment at the Sol 718 stop, the odometer would continue counting until it was reset at the Sol 719 stop.

• A lot of sources, I'm also inclined to thrust them, thanks. Mar 7 at 8:29