Foot pod running outside.

BTW, originally I wrote the app, to see where and why the watch is using the accelerometer or hrm/pod pace instead of the GPS speed. So I compare the built-in pace (mix of GPS and accelerometer data) and the GPS-only pace, and hence can see where the watch switches from GPS to the accelerometer (regardless whether internal or external).

Bitti said:

if the foot pod pace is set to "indoors only", do you really think that the watch starts still using its pace if GPS reception is poor enough?

Yes, it does, I am sure about it, just because I observed the data rather closely, and for a long time. As far as I could see, the watch switches from the GPS pace & distance to the accelerometer data minimally in two situations - when the GPS quality drops, and/or when the GPS pace reports back some extreme values (very slow or very fast). The algorithm may be more complex than just that, but it is certain the watch switches from the "outdoor" mode to the "indoors" mode even during GPS activities rather frequently. And in such case, it then indeed uses the data from HRM-Pro of from the foot/RD Pod, even if you keep the setting on the option "indoors only"

Edit: that told, I think the switching to the indoor mode (and hence to the accelerometer data) might have been introduced just a few years ago, and may not be used at some old models, or at watches with old firmware.

I was wondering about that for a very long time, thank you for investigating and explaining how that works.

Thanks, that was very informative!

... and another note - even if you disable the pace & distance at the foot pod (or at the HRM) completely, the watch will not stop switching to the indoors mode during GPS activities anyway. Just, instead of using the external sensor, it will use the internal accelerometer & gyro (not all models have the gyro though!). And it typically means much worse pace and distance deviations, because the internal sensors are much less accurate than the external ones -  especially because of the very complex curve the watch is moving on during a run, being worn on the swinging arm. The accuracy is usually better on a bike, where the watch moves more or less without any parasitical trajectories.

Ok, thanks! So that means that even though I never run on a treadmill, I still should keep HRM Pro+ pace as "indoors only" (the default, which my also my current setting), and it could sometimes still benefit outdoors running.

I've sometimes though that it would be interesting to compare the pace/distance accuracy of a real foot pod and HRO Pro+ for outdoors running. On the other hand, a real foot pod gets data from the foot which actually does the running, but then on the other hand, HRM Pro+ measures the acceleration at the torso, which means that it doesn't have to compensate for the periodic movement of the foot (and gets similar data from both feet). You wouldn't have happened to already test that?

That explains the awful bad pace data I used to have during trail runs under dense tree cover whenever I had forgotten the foot pod. This was with a Fenix 6, maybe 7 does a better job, not tried it, I did not forget the foot pod yet.

Bitti said:

Ok, thanks! So that means that even though I never run on a treadmill, I still should keep HRM Pro+ pace as "indoors only" (the default, which my also my current setting), and it could sometimes still benefit outdoors running.

Yes, exactly. It is not "sometimes". It is surprisingly often. When I compare runs on the same track with a relatively good GPS signal, the accuracy without HRM-Pro (using internal accelerometer when switching to the indoors mode) is some 10% off the true distance, while with the strap it is in the range of 1%. So to get such a difference, the "indoors mode" must be used more than the couple of seconds, where I am seing the GPS signal to drop out (mostly bridge underpasses) in the detailed data.

Bitti said:

On the other hand, a real foot pod gets data from the foot which actually does the running

The recent RD Pod is actually supposed to be worn on the waist, not on the foot anymore, just to eliminate the complexity of the movement of an accelerometer/gyro device when worn on the foot (or on the wrist). I do not own any foot pod, so could not make any tests with it. Well, I could use the data from my friend, who has the RD Pod, but then he wears it on the waist, so it will be likely behaving practically identically to the HRM-Pro.

At least for trail running in Finnish forests, I wouldn't trust instant pace derived from my foot movement either. Too much random shuffling, steps to the side, etc.