Underestimating pace with Venu 2

I went running with a friend who has Garmin Phoenix 6s. We stuck together the entire time, but mappily gives me an instantaneous pace that is way better than my friend’s. Also my average pace per lap is always better than his. We are talking around 10 to 15 s/km difference. I noticed this a few times. When I use my Venu 2 normally (no mappily) I have no such issue (this I also compared a few times).
I think mappily is marvellous, but this is quite annoying as I’m training for the half marathon and it took me a while to figure out. Any chance this can be looked into?

Hi Welcome! Can you confirm you are using instantaneous pace rather than the smoothed 30/60 second versions?

Also, when you finished your run was the pace that got uploaded different to the pace you saw as you were running?

It sounds like you’re using min/km on the watch rather than miles, is that correct?

Mappily uses the native activityInfo.currentSpeed (Toybox.Activity.Info (garmin.com)) value and then uses some basic maths to convert to pace.

If you’re willing it would be useful if you could add the Speed field to your watch and confirm whether the speed shown is correct, or is slightly too high. This would tell me whether there’s a potential error in the calculation I can’t see right now.

Was the total distance and time of your run correct? Is the average pace correct while the current pace is incorrect? An issue with both would indicate a GPS problem rather than a calculation issue.

It is possible that Garmin are doing some minor smoothing to the instantaneous value which we are not, but that wouldn’t account for constant under-estimation.

Hi David, wow thanks for replying. Let’s see:

Yes, I’m using min/km.

My bad, the pace my watch was displaying is the average pace, not the instantaneous one, nor one of the smoothed ones.

My friend and I both uploaded our run to Strava. It’s clear my avg pace/km is always better than his. It looks like the displayed average pace is really the issue.

The estimated distance was roughly 100m more than the one from my friend (8.93 for me, 8.82km for him). But that alone also doesn’t completely explain the pace issue. It’s quite weird however.

I can include the speed field in my watch, although I’m not sure how to validate it…I should probably compare it with my friend in the next run, or with my phone. As I understand it, if that field were to be off, the problem would relate to the watch itself, is that right?

I plan anyway on comparing the data from next run with my phone.
Thanks so much for your help, if there’s any data dump that you may be interested in, let me know

Thanks for checking. The displayed average pace is always the raw moving time divided by the raw distance. If the value displayed is off, one of those values must be incorrect, but it’s unlikely to be wrong as its such a simple calculation and it hasn’t been reported previously.

Check that the final displayed distance and moving time calculate to the final displayed average pace. I can’t see why they wouldnt

Being within 100m sounds good, so could it just be that his watch is autopausing when yours isn’t, or vice versa. Any tiny pause is likely to have an effect. Check the moving time carefully. That is what Strava uses for pace