Running Distance / Pace calculation is flawed / needs rework

Hello, A while ago, I reported that my Fenix 8 watch under-reports distance by a large (from a training athlete's perspective) amount, resulting in wrong running pace reported. 

This affects someone who is actively training both during running - pace is under reported, as well as post training and in planning. 

On today's 7km run - as reported by the Fenix 8 - the recorded GPS track distance was actually ~7.55km. So the distance is actually being recorded correctly, but the watch applies (as I've learned in the previous post) some corrections / calculations based on stride length and cadence, to figure out distance, and purportedly ignores the GPS track distance. 

Garmin has also recently removed the ability for users to specify stride length manually - so you are stuck with what the watch "thinks" is your stride lenght based on accelerometer data, etc. 

Now - to me as a runner who is actually training - distance is distance, based on map data and gps track length - not a calculation you are stuck with and have no control over. In today's run as reported by my F8 my running pace was 5:05min/km over a distance of 7.02km. But based on the recorded GPS track and MAP data - I had a running pace of 4:44min/km over 7.55km. These are two VERY DIFFERENT running paces / running zones, pertaining to DIFFERENT TYPES OF RUNS for DIFFERENT END GOALS within the training block. They cannot be used interchangeably!

Which one should I - an actively training runner - take as correct & accurate when running and planning my training block, with my top-of-the-line flagship sports watch

Has anyone ever found a fix or workaround to have the ACTUAL track distance/map distance reported on their activities instead of useless calculations? 

Also a note to Garmin - shouldn't you put a better use to your "athlete intelligence" technology - to analyze post-activity data and apply corrections based on hard facts (map topographic and survey data for distance / elevation) and IMPROVE such a CORE FEATURE of your devices like Running, instead of using it for shiny "golden badges" and an "intelligent insight" that tells me that my recent stress of 23 is lower than my average past stress of 25??? Slight smileSlight smileSlight smile Current features like HILL SCORE and ENDURANCE score are utterly useless (algorithms are wonky and elevation data gets skewed by the slightest change in ambient pressure or temperature)

Why are athletes penalized when this is a "SPORTS WATCH" and we are getting newer and fancier "smartwatch", "wellness" and "social" features instead of focusing on having a ROBUST and ACCURATE training experience on a thousand dollar Flagship sports watch??!! 

  • Finally I will say that I share your frustration with Garmin. I've seen a ton of issues with Garmin ever since I started using their running watches, so I'm not exactly trying to defend them here. 

    I'm just trying to clear up what I see as some misconceptions regarding avg stride length vs instant stride length and avg pace vs instant pace.

    Both avg stride length and avg pace are straightforwardly derived from other measured metrics (like time, distance and avg cadence), so they don't really give you any additional information about whether your run data was good or bad, beyond what the distance itself tells you. Average pace is time / distance, simple as.

    For example, assuming the activity time is good, then if the measured total distance is good, you *know* the average pace will be good. If the measured total distance is bad, you *know* the average pace will be bad. Looking at the average pace gives you no additional information about whether the run was good or bad compared to looking at the distance, and vice versa.

  • This has been an ongoing issue in Fenix 6, which Garmin has never fixed. There are multiple forum posts about Fenix 6 distance being too short and pace being significantly biased on the slow side.

    Then in Fenix 7 Garmin used a much better GPS chip, so this issue has mostly disappeared, although based on some evidence I suspect that Garmin has never changed the algorithm.

    Now in Fenix 8 and Enduro 3, Garmin has changed GPS chip again to a worse one than in Fenix 7, so this issue has resurfaced again. While Fenix 8 and Enduro 3 are more accurate than Fenix 6, these watches are not nearly as accurate as Fenix 7. This is especially evident when running on trails in a dense forest. 

  • Ok, did a test on board the cruise ship. First using Stryd I started a Run, but I actually walked, recorded 300 m in about 5 minutes. Seems the distance was reasonably correct. The disconnected Stryd and let my Fenix 7 use GPS. Doing the same route gave me 2.76 km in 5 minutes. Just as expected the ships speed made a big impact. Whether this has any bearing on the current discussion, I have no ideaGrin

  • Whether this has any bearing on the current discussion

    Sorry, but it does not. TBH, using GPS for getting the walking distance on a moving ship appears to be a plain foolishness to me. If you want to compare it with Stryd in indoor conditions, then use Indoor Walk, Treadmill, or simply disable the GPS.

  • Whether this has any bearing on the current discussion

    Sorry, but it does not.

    It does, actually. It confirms that when GPS signal is available, the watch uses GPS distance over accelerometer data to evaluate distance (even if it is irrelevant, such as running on a moving boat ^^ )

  • It confirms that when GPS signal is available, the watch uses GPS distance over accelerometer data to evaluate distance

    We know and always knew, that the GPS is the main source of distance data at outdoor activities, so it does not really help with the case reported in the OP. The problem is that the watch often resorts to the accelerometer data even when the GPS track is accurate, which can be easily verified by checking the track on the map and then comparing the track distance with the distance reported by the watch. 

  • I noticed similar issue on my Marq Athlete gen2. From some time, on the same track, even i felt i was pacing very well I was unable to reach pace i did before. Today i made check. On distance of 16km, watch is not calculating about 400 meters of distance - 16.4 km is clearly calculated by GPX viewer. It means, my calculated pace is slower about 90 sec per whole race !

    I am running 20km per day. Average pace from 2025 distance is about 3:50 when now it is hard to reach 4:00, even on stadium without wind, in steady condition. This i not acceptable....

  • After the latest firmware was deployed I've had a track day that came in within 0.1m of the GPS track distance. I thought the issue was somehow quietly fixed, but unfortunately not. The subsequent run (20km) had a track length of 20.9 km. Both days were similar (no GPS obstructions and clear skies). 

  • Yeah so I was wrong when I said that average stride length is calculated from distance, time and cadence. I double checked with a couple of newer activities and avg stride length doesn't quite line up with those metrics. At least for modern watches, it might actually be the average of instant stride lengths or something like that. On watches without instant stride length, the other way might have be how it was calculated.

    Average pace is def calculated from distance and time tho (as can be seen if you edit an activity's distance or time), as opposed to being the average of instant paces. Also wanna say that a clear sign Garmin themselves don't think instant pace is super precise is that they round it to the nearest 5 seconds during the activity (although not on the instant pace graph after the fact). I will stand by my point that instant pace is somewhat divorced from average pace / lap (average), meaning I don't think average pace is *strictly* determined from instant pace. (But rather, average pace actually always is simply time / distance, and distance probably isn't determined by "summing" the instant paces.)

    Sorry for the noise and I'm sorry that you guys are having issues here. (Ofc the issues would still be issues regardless of the above point or not.)

  • Yeah so I was wrong when I said that average stride length is calculated from distance, time and cadence. I double checked with a couple of newer activities and avg stride length doesn't quite line up with those metrics. At least for modern watches, it might actually be the average of instant stride lengths or something like that. On watches without instant stride length, the other way might have be how it was calculated.

    Average pace is def calculated from distance and time tho (as can be seen if you edit an activity's distance or time), as opposed to being the average of instant paces. Also wanna say that a clear sign Garmin themselves don't think instant pace is super precise is that they round it to the nearest 5 seconds during the activity (although not on the instant pace graph after the fact). I will stand by my point that instant pace is somewhat divorced from average pace / lap (average), meaning I don't think average pace is *strictly* determined from instant pace. (But rather, average pace actually always is simply time / distance, and distance probably isn't determined by "summing" the instant paces.)

    Sorry for the noise and I'm sorry that you guys are having issues here. (Ofc the issues would still be issues regardless of the above point or not.)