Ultratrac is inaccurate, so anyone have an on-wrist charging solution ?

Hmmm, quite hilly terrain as well?

Basically ultratac is very infrequent gps positioning afaik so I am guessing it will use the other sensors to 'predict' your directing and distance... Hilly environment adds uncertainty to the actual gps points and if the path is a bit swerving it will assume you go straight on, overcorrect on the next gps point, rinse and repeat...

So I guess that both adds to the incorrect distance.

Afaik there is no solution for on the wrist charging unfortunately (quite strange as I can't imagine it being too hard to create an angled cable of some sort)... A small powerbank and cable are all you can do atm.

And hell, kudos on finishing that! Insane (but I am guessing beautiful and awesome as well)

I walked the WHW over a week, and that was exhausting enough. Awesome achievement to run it.

The watch would probably only need about 30 mins of charging along the way to get 30 hrs - could be done in 5 min bursts at aid stations, or short periods attached to your pack rather than your wrist.

Thanks, I'm not sure when I'll next need the watch to last as long, but will try hacking together a cable for on wrist charging or do the occasional off wrist top up as suggested.

Have you considered a foot pod so you don't rely on GPS for distance? Stryd is usually accurate within 2%, even when uncalibrated.

Yes I had considered a footpod, but from what I read the Garmin footpod doesn't help much and the Stryd only has 20hr battery life. I also didn't want any extra weight on my feet (don't mind a little on my body).

Since I wanted HR I hoped that the HRM-Tri accel/gyro would help supplement the wrist based accel/gyro to improve Ultratrac accuracy and on my shorter runs (up to 60k) distance looked within a reasonable 3%

What about the Garmin running dynamics pod?

There have been posts over the months about on-wrist charging for the 935. If my memory serves me correctly, someone came up with an angle cable and wore the device with a sponge cushion underneath it. Not sure whether the image I'm visualising is a 935 or another device. If you trawl back through the forum posts you might find it.

I twas wearing an HRM-Tri which I thought gave the same run dynamics data as the pod (vertical oscillation, ground contact time, etc). Is the pod better ?

I had a search on the forum and found various suggestion of hacks using sponges, etc as you describe, but since those threads were 6-9months old I was hoping some enterprising company had made something a bit less ghetto :D

Anyway my legs are telling me it will be a while before I try anything >24hrs again, so will revisit closer to that time.

Many thanks for everyone's suggestions

I'm a bit of an UltraTrac addict and find your track captivating. Like if you hadn't stated that you were using UT, I wouldn't have suspected that by viewing your track. I'd guess that the gyroscope is doing a lot more than what I originally believed. I was under the impression that it only aided in navigation when following a course. Obviously it is simulating GPS coordinates and using that info to create additional track points in the data file. Now whether or not it is using that data in performing it's distance calculation is beyond me. I'd have to really crunch the data file to determine distance sourcing. My experience using UT is a Fenix 3. That's pre-gyroscope implementation. My tracks don't look anything like yours so I don't think my analysis translates to the Fenix 5/935 product line.

Anyway, I don't have any conclusions on if the over accumulation of distance was general GPS noise or simulated noise from the gyroscope or stride changes at slower speeds. Probably a combination of all three. I do concur with the recommendation that topping off the battery at periodic intervals is a great choice in GPS mode and then generally unnecessary in UT.

So while I can't add any value to your questions I have to add additional kudos to your accomplishment. Very impressive!!

I took a closer look at some of the trace and the attached screenshot is one of the worst sections. The trail is the white line across the middle, I am moving from right to left. Trace starts off not to bad then wiggles dramatically (more than 500m off the trail and then back) towards the top off the hill then settles down again. I reckon this section alone added an extra ~4km to my total distance. It was in a valley with mountains either side, but it was quite a wide valley (not a canyon) so reasonable view of the sky. There are other wiggles like this, but not as dramatic.ciq.forums.garmin.com/.../1355625.png

What about the Garmin running dynamics pod?

The RD pod won't help because it only gives running dynamics, but no pace nor distance.