Enough with the “My Garmin says the race course was long”!!!

I’ve got a little rant. And to be fair, I used to think the same way as the people who do this when I first started running. But enough already. 

Garmins and other GPS watches/apps are fantastic tools to help with running. They are pretty amazing devices. But they are not infallible. The way the technology works is pretty darn smart, but it is hardly precise enough to rely 100% on. Basically, the watches ping off satellites far, far away about every 10 seconds and are able to to mostly pinpoint where you are located. But there can be a lot of “noise” around those signals, including trees, buildings, even by so many other runners accessing the same satellite simultaneously, etc. 

Most race courses are very, very carefully measured multiple times by nifty gadgets used on a bike. These measurements are often certified. And also, these measurements are going to be a heckuva lot more accurate than your Garmin. [An aside, your Smartphone apps are usually even less accurate than a dedicated device like the Garmin. I used to run using both, and the phone app was always more optimistic about my pace. I recently ran with a friend who uses Runtastic, and his data said we ran 5.7 miles while my Garmin said we ran 5. Boy was he bummed.] 

Have you ever looked at the mapping of your Garmin data after a run and seen that it looks like you cut corners when you know you didn’t? Or as if you ran through a building? Go ahead and look at your Garmin data for a race you felt the course was long or that you ran the tangents poorly. See if your running map closely matches the actual course. 

I just ran the Rock n Roll Philly half marathon on Saturday. The first three miles were in the middle of Center City. 

My Garmin beeped about a minute before I hit the first mile marker. No, the mile marker was not wrong. My Garmin was wrong. Here’s a graph of those first few miles. See how erratic it was? I promise I wasn’t jerking along the race course, going uber fast then stopping. 

What was happening here is that the watch got confused by all the buildings. On the map, my run looks like this:

You can see it looks like I ran through some city blocks. I’m Superwoman, flying right over buildings! If this picture doesn’t convince you, here’s a close up:

I have no idea what was going on here. I was stumbling through Philadelphia, apparently. I won’t bother posting the graph, but the elevation charts are all over the place on my GPS recording, but except for one dip down then up under an overpass, this section of the course was very flat.

Here’s an example of one time when I was running on a track. This kind of mapping error accumulates. I’ve realized if I want more precise workout feedback that it’s better for me to use a simple stop watch for track workouts or to turn off the GPS and use the calibrated footpod. It’s doubtful the tracks I run on are long, so it has to be that GPS isn’t perfect. 

According to my Garmin, during the Philly race I ran the first three miles in 8:18, 8:21 and 8:13. Not that I’m not capable of running those paces, but I didn’t on Saturday morning. I ran this race as part of an 18 mile training run. I ran 5 miles before the race started then planned on running the race at around goal marathon pace. I was running by feel (had my arm warmer covering my watch, but I have it on vibrate for the mile laps), and I knew I wasn’t running that pace. The timing mats had me running the first 5k in 27:18, which averages out to an 8:48 pace. Right on target. 

Once we left Center City, my watch tracked much better with the course, although by then it was about 3/10 of a mile ahead of reality. I had something similar happen when I ran the NYC Half in March. My watch lost it in Central Park and rather spectacularly in Times Square. As much as I’d love to believe I ran a 4:40 mile through Times Square, it didn’t happen. I missed my goal for that race because I was depending on Garmin, and Garmin was all over the place for the first 8 or so miles. I thought was running much faster than I was. The good thing was that I realized I had a problem when I hit Times Square, and I gave up looking at the watch and ran by feel. This was the first time I’d tried it, and it was largely successful. I still missed my goal, but my second half of the race was right on target. My body knew better than the watch what pace to run. 

My race in Philly went really well. I ended up running the last 5k faster than marathon goal pace (about an average of 8:28/mile) and faster than the first 10k. You can see from the RnR results page that I picked up speed after the 10k mark. It’s nice when this happens, especially since I’d run 5 miles ahead of the race and was feeling strong by what was about miles 15-18 for the day. I felt relaxed and comfortable — confidence boosting for my marathon in 6 weeks. 


According to my Garmin, I ran 13.4 miles. While I didn’t fuss over my tangents and probably could have run them more efficiently, that isn’t what accounts for the excess 3/10 of a mile recorded by Garmin. It was watch error. And I’m telling you, while it is possible for a race course to be off due to human error, the vast majority of the time it is the correct distance, NOT what the GPS device says. 

I used to want to believe the Garmin because it certainly puts my running ability in a more flattering light. But it’s not reality, and in the long run, it doesn’t serve me to deceive myself. It’s also better for me to not be so reliant on that little wrist-sized bit of technology. I’ve learned to trust myself and enjoy running more by staring less at the watch. 

If you don’t believe me, go back and look at your own data. Do a little tough critical analysis. You can thank me later. 😉


28 thoughts on “Enough with the “My Garmin says the race course was long”!!!

  1. I always knew you could fly over buildings.

    I don’t fuss when Garmin reads “long,” but I worry more when it reads short until I can look at the map because I want to make sure that I ran the full distance.

  2. AMEN, SISTA!!!! Everyone should know that you always run more than 26.2 miles in a marathon, too. My garmin was so whacked last week, it was off .2 in ONE MILE. Then it was saying that my paces were in the upper 9’s, when I was out of breath, which I know was wrong. I think it was this one tree in the way ;0
    I figured that I’m going to really need to know my race pace before my marathon, as the Garmin is only a tool. I was even thinking of going without it and just using a watch and times written on my arm like the old days. But I don’t know yet….

  3. I’ve had odd routes show when I uploaded my data also. One time I ran across a lake! In the summer. All this while I was driving home!
    I like to believe that my Garmin is accurate, but I have to settle for, “it’s good enough.” I’m not training for The Olympics, so it’s no big deal if my splits are not 100% accurate.
    What I really love is when the watch shows me running some unbelievable pace. How about the maximum pace during a split? I’ve run at a 5:00 pace for at least a split second according to Garmin. Now that’s encouraging! 😉

    • Lol! You’re Jesus running on water!

      I definitely subscribe to the “good enough” opinion of Garmin’s data. It’s an extremely useful tool. I just feel like I’m doing myself a disservice if I overestimate my ability. But, yeah, my Garmin claims I ran a 1:25/mile for a split second during my half marathon! Cracks me up.

  4. I stopped relying on GPS on my first trip with one. My friend and I wanted to eat lunch in Tennessee before heading up to Kentucky. The silly thing directed us to an open, grassy field. If I’d been a horse, I would have been a happy camper, though those who owned the park might not have been impressed. 🙂

  5. Yes! I’ve had to explain this to SO many people! Between satellite interference and the fact that no one EVER runs perfect tangents, your GPS should almost never be accurate to a measured course. I’ve only found maybe 3 instances in the 100 races I’ve run where the course distance was legitimately off, and those were tiny mom-and-pop uncertified charity races (where the organizers weren’t runners & didn’t know better) and a triathlon (which notoriously “round” distances). For once & for all: the Garmin is wrong, the USATF course certification is right.

  6. Absolutely 🙂

    For me the only useful quantitative analysis is when you run the same course over and over again at the same time of say and can build up a data set based on your GPS triangulating from the same satellites.

    Also worth noting is the difference between ‘smart GPS’ (like the low- to mid-range Garmins and many other <$300 GPS watches) compared to 1 sec data collection schemes … the 'smart' ones will lose your more abrupt moves (though mine does OK with the cul-de-sac at the end of our road).

    But ultimately I look at it like this:
    – If this is a 'BQ Course' … trust the course. It doesn't matter how many 'Garmin chirps' you hear 50-100 meters before / after the mile marker … it just means you have the same slightly inaccurate hardware 🙂
    – If this is a 'fun run' and you are stressing over 0.1 mile … go back and remember – this is a fun run!
    – For stuff in between, just remember that the likelihood of an inaccurate course is much lower than the chance of either how you ran the course not matching the midline measurement, or of your watch having small inaccuracies – and most likely a combination of both.


  7. Totally agree. Trust the course people, lol!
    This weekend’s race was no where near buildings as Arizona is flat and there’s nothing anywhere, lol, so when everyone’s watches beeped waaay before the mile mark, several times, I chalked it up to the race being in its inaugural year so there could be some discrepancies. It was like that the entire way where our watches beeped way before the mile mark. When we finished though, we weren’t that far off, maybe .15ish which isn’t horrible. I think this may have been a random instance but when I hear people legit blame races, I laugh. I actually hate when people make *any* excuses for why they’re not happy with their time, lol! Own it!

    I’m a grump! 🙂

  8. Darlene says:

    I hear ya. It drives me nuts. I do think my Garmin is more accurate than the Runkeeper app on my phone. This weekend I ran a 5k in NYC and I think I lost a satellite during mile 2 since I slowed down at a water stop, yet it was my fastest mile. Yet the course still showed over 3.2 miles???

  9. kilax says:

    Hee hee, and how about the people who go by what their Garmin was at for the official race distance and use that as their finishing time? (For example, if they ran 13.3 at a half, they’ll look back at the time they hit 13.1 in, on the Garmin). LOL. Cracks me up!

    • Oh yeah. I know a woman who has run the exact same marathon course more than 5 times, but this year decided that she PR’d when her Garmin said 26.2. What, this race that’s been around for decades is suddenly long this one time just so she can claim a new PR? Just NO.

  10. Haha, love this. My Garmin is usually all over the place. It’s had me running across a lake and breaking through neighborhood backyards. I figure as long as it’s long rather than short during a race it’s all good.

  11. I love it when I’m cycling beside the sea and it shows me underwater for most of the time.

    2 points

    I use a Garmin edge on the bike and wonder if the bigger battery gives more accuracy

    Does the movement of the wrist affect results, there’s possibly less on a bike handlebar, still odd results happen even then.

  12. First of all – fantastic “training run!”
    Second… yes to all of this. I personally don’t understand what the big deal is about a couple 10ths of a mile. Maybe I am just too casual of a runner. If a race is MILES off (like GAP trestles marathon was), I will get a little irate. Then again since I do mostly trails half the time a 25k can mean anything from 14 miles to 17. That’s IF you stay on course that is, so maybe I’m a little more laid back in that regards. But people need called out on this. Hardly anyone runs perfect tangents. Garmins are not perfect. and again, WHO REALLY CARES. Ok… I’m done being ranty.

  13. Doug says:

    That they have three satellites measuring signals from something affixed to your wrist that emits signals traveling at the speed of light and measuring and triangulating the time of each with such precision that they can even get close to where you really are is incredible. At least that’s my understanding of how they work. And considering my step daughter can’t get to work on time to her job less than three miles away, I don’t think it’s my place to judge the shortcomings of geosynchronous technology. But that’s just me, feel free to rant to your hearts content.

  14. Doug says:

    Yeah some people are a little too dependent on technology. The a fore mentioned step daughter would walk through a plate glass window if her GPS told her to. I can be riding with her telling her she is about to go the wrong way on a one way street (metaphorically) and she will argue with me telling me it can’t be one way because her GPS would tell her so. I really don’t know because I actually look where I am going.

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