GPS accuracy - do you trust your run stats?

[backintime]

Hi

This weekend I did my first 14K run - or did I?

I was playing on my commute this morning with the runkeeper app and zoomed in on my route I ran yesterday.

It was a bit all over the place, which I understand, and I expected it to be a bit out which is why I did 300m extra to try and make sure I did the 14K. I found the "smooth it out" option (or whatever it's called) and it lowered the distance to a smidge over 13k.

I know sometimes I was all over the place avoiding things and going through those zig zag gates that are all along my path.

I suspect the truth lies somewhere in the middle (and I am selfishly hoping it lies closer to 14k than 13k) but is there an "accepted" percentage of error? Do you all just go by your stats and think it all balances out in the end?

My phone is on "high accuracy" as far as GPS goes and it is carried in the back zip pocket in the waist band of my joggers

[GoGo_JoJo Ultramarathon]

There's an option in Strava on the web access to "correct" distance based on known distances. Whenever I try it it adds more on. I get the odd blip when Garmin adds a spike to the route that I know I didn't do but overall I just accept them. Its close enough. 👍🏻😁

[Maddee_6333 Half Marathon]

Because I generally have two trackers going - I like to have MapMyFitness tracking in case of getting lost - I am used to them disagreeing about how far I’ve run. I just have to accept it.

It’s close enough.

And let’s face it, when we enter an event not everyone runs the same distance as everyone else, anyway.

[backintime 10 Miles in reply to Maddee_6333]

I agree, I am just trying to improve my pacing. I did C25K and Bridge to 10K on a treadmill which did my pacing for me and I have my app calling out stats every 500m so that I can guage my speed and slow down if I am moving off too fast. If the gps is way off and I'm slowing own or speeding up based on it then I just wanted to know

[Stephen_UK Half Marathon]

I have found RunKeeper generally very accurate, but it always underestimates distance by a small percentage. So for 12K I have to run nearly 12.5K for the app to log that much distance. This is because it shaves off a metre here and a metre there on corners, and over time those lost metres all add up.

If it goes REALLY wrong, as has happened only once in 50+ documented runs, you can log in to RunKeeper online and simply correct the route. This is satisfying if you ran more than it said, but obviously less pleasing it if ends up reducing your final distance.

[backintime 10 Miles in reply to Stephen_UK]

I hit the "smooth it out" option but it knocked 1.3km off, which seems too much percentage wise for a 14K run

I will just go with it and make sure I run 300-500 extra metres on each run to make sure I am running the distance lol

[Stephen_UK Half Marathon in reply to backintime]

Never use the "smooth" thing, because it is just using guesswork. Better to go in manually (far easier on a computer than on a phone) and simply correct the lines to match what you ran.

P.S. RunKeeper measures my Parkruns to within 10 metres of the 5K distance, so that seems pretty accurate.

[backintime 10 Miles in reply to Stephen_UK]

That would imply I know what I ran

There are lots of those gate things that you have to zig zag in and out of and running around dogs and puddles and stuff, I will just make sure I run a bit extra. It was mostly for the pacing though, as I am still learning that bit as the treadmill did it all for me

[Tasha99 Marathon]

Got to go with garmin 👍🏽

[UpTheStanley Half Marathon]

There’s no way zigzagging is going to add 0.3k to a 14k run, let alone 1.3. But if it somehow did, that’s the distance you ran anyway, or would be as far as I am concerned 😀

[backintime 10 Miles in reply to UpTheStanley]

Thanks..I didn't think it added more than 20 or 30 metres in all, but I am hoping, maybe childishly, that my 14.3k is more like 14 than 13 : )

[UpTheStanley Half Marathon in reply to backintime]

I would expect it's closer to 14.3 than 14.0, personally, and just think you're beating yourself up unnecessarily. If you really don't trust Runkeeper, perhaps you should ditch it in favour of a watch. I just believe my Garmin 35 - although its track showed me crossing the Avon gorge without using a bridge during the Great Bristol Run, the measured distance only came out at 140m over the official 10k.

[backintime 10 Miles in reply to UpTheStanley]

My 7k event in Paris came out as 8.1k...which is one of the reasons I'm asking. I slowed down based on the feedback ie got to 1st and 2nd km fast (thought I'm going off fast because of eveeyone else) and maybe I hadn't covered the distance I thought....I suppose pace will come with more experience

[backintime 10 Miles in reply to UpTheStanley]

Look at you running on water ; )

[cheekychipmunks Half Marathon]

I’ve given up using MapMyRun along with my Garmin on runs like I used to. On two separate occasions, on the same route, MMR left out a whole km on different parts of the run which threw my stats totally.

I find Garmin measures PR pretty accurately whichever course I’m doing. It’s just a few meters either side of 5k, so I’m happy with that. The furthest it’s been out is on a recent 10k race as it came in at 10.23k. That’s unusual though. 👍

[mrrun Ultramarathon]

Stats and accuracy made misery out of my son's life. He's a competitive swimmer, early morning training and hard shifts are reality and he's now had enough of it. Doesn't want to do it any longer. Fun's gone. At 16. Good boy, and l respect him!

On the other side of spectrum l run for fun. I have no watch, do no race, own no stats but have reached the stage where nearly all of my runs are leisurely 10k with no pressure. Am I fast or slow, struggle or not, irrelevant or important? Who cares, when it's fun, it's fun. 😀

[backintime 10 Miles in reply to mrrun]

I completely agree...I just want to know if I'm running too fast (for me) so won't be able to finish my distance (I have signed up for a HM). I am not aiming to go faster or beat a pb.

I did all c25k and bridge to 10k on treadmill which did my pacing for me. Now I am in a weird position of being able to run 14k but no "feeling" of pace. Hence my "dependance" on pace feedback from my phone

[Hidden]

I would trust my watch over an app in my phone. When I had the Garmin Fenix, it used to sometimes lose gps and drop part of the run. The Polar Vantage V is more accurate. But who knows for sure? They are all prone to deviations

[UpTheStanley Half Marathon]

Before the advent of "tech", I used to measure distances off a map using dividers and a piece of string, and make a mental note of the milestones …… if you know where you're going to go , it's really easy to do that now using Google maps satellite view (right click on your start point and select "measure distance"), easiest when the roads are straight of course.

[backintime 10 Miles in reply to UpTheStanley]

I use onthegomap.com to create routes and it snaps to the roads bit when I'm off road or the road isn't official it doesn't do it.

[Stephen_UK Half Marathon in reply to backintime]

If you do this on the Mapometer website you can switch ‘snap to roads’ on and off during the same route-planning session as many times as you need. This is a big help because you can switch it off to factor in your own off-road shortcuts AND switch it on again to get the benefit of quickly measuring longer road-based parts of the route.

[backintime 10 Miles in reply to Stephen_UK]

Thanks..I'll look at that

[Sqkr Half Marathon]

I don't worry too much about distance to be honest. I break my runs up into short (3-6k), medium (9-15k) and long (>15k) and as long as they fit into the appropriate category the actual distance doesn't worry me too much. Everything has quite a big error margin round here for whatever reason, be it tree cover or hills, or just a sluggish GPS connection, so I never really know accurately how far I've run. I usually go by the Garmin for consistency, but I know it underestimates on hilly routes. I don't smooth anything, that just starts introducing additional algorithms and rounding satellite data, so will potentially be even less accurate. I think the more you run the less you worry! I'd say just stick to one measuring device and use that as your baseline, you'll soon get a feel for your pacing.