Which is correct? Your Garmin or the RD? (Read 325 times)

    Yeah I know it's a rhetorical question, Hasher Rick, but still...


    Uncertainty is woven into the fabric of the universe.


    Also, here's one of the millions of threads on GPS accuracy on Running Ahead dot com.


    And another.


    And then, of course, there's the old "In GPS we trust" article.


    Eventually all of these GPS accuracy threads will reference each other and cause RA to implode but it won't be my fault.

    Runners run.


      Courses aren't necessarily marked correctly. Assume both the mile markers and the GPS have errors.


      if you wear two GPS watches, one in each wrist, you'll get different distances. If you wear them in the same wrist, you'll probably get the same reading (or something close to it).

        Some RDs are contentious on purpose.



        Actual course marker.


        It's a love-to-hate sort of thing, though.  Oddly, that was one of my only races where the official distance and Garmin distance were exactly the same.

        "When a person trains once, nothing happens. When a person forces himself to do a thing a hundred or a thousand times, then he certainly has developed in more ways than physical. Is it raining? That doesn't matter. Am I tired? That doesn't matter, either. Then willpower will be no problem." 
        Emil Zatopek

        Prince of Fatness


            I don't have time to read the whole thread, but the thread caught my eye as someone who makes his living from GPS and has done a LOT of testing (of self and with data from thousands of others, actually).


            I *almost* always trust the RD if the course is certified.  That being said, I have also learned that it is more common than it should be for the race not to be run along the certified path.  Sometimes this is the fault of the cop ahead of the lead runner, or the fault of volunteers who don't understand where they are supposed to direct people, etc.  In one case I know of, I think it might be likely that the RD did not pick up on a seemingly subtle course change made by the certifier (or maybe the certifier didn't follow the proposed path given him by the RD).  In any case, GPS, in my view, is sort of a nice "sanity check", but on most courses it (at least on one major manufacturer's products) will give a slightly long distance by about 0.5 to 1.0%.

            - Joe

            We are fragile creatures on collision with our judgment day.

            YAYpril - B-Plus

              My watch has recently decided (in the past 6 months or so) to always measure short. I'll run with my RP and come up .2 mile short (compared to her watch) on a 10-mile run, and my last 3 races were 6.13 (10k), 13.14 (HM - last year I ran the same course in 13.2; I'm not THAT good at tangents) and 3.04 (5k). I trust the RD because I know my watch is wonky.


              If I didn't have a watch, I would HAVE to trust the RD. So what changes because I do have a watch? Nothing. Especially since I know the watch is always short by a little bit.

              Biking Bad

              finnegan begin again

                I like hearing Garmins beeping as we near the first mile marker. They are fairly close. Then as the distance extends, so too does the Garmin beeping. It's difficult to not laugh as someone begins to declare the markers wrong or the course length inaccurate.


                Not saying it couldn't or doesn't happen. But the worship of the device is more evidence of the shear lack of technology, logic and reasoning.


                Around here, the 2 prominent timing services (Smiley Miles-Herb Cratty and RunHigh-S Mark Courtney) are very particular in measurement of their Certified courses. I don't think they use Garmins for certification.


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                  I don't think they use Garmins for certification.


                  They don't, because the only device approved for course certification per USATF rules is a Jones Counter.

                  Runners run.


                    Oh the length of the certified course vs the garmin is fine.  But I KNOW they sometimes place those mile markers any ole place!


                    Running is stupid

                    A Saucy Wench

                      Some RDs are contentious on purpose.



                      Actual course marker.


                      It's a love-to-hate sort of thing, though.  Oddly, that was one of my only races where the official distance and Garmin distance were exactly the same.


                      You need to be a bit more specific...

                      I have become Death, the destroyer of electronic gadgets


                      "When I got too tired to run anymore I just pretended I wasnt tired and kept running anyway" - dd, age 7

                      100K or Bust

                        How disappointing to learn that Garmins aren't accurate. I was sure I had identified a half asleep Ent that moved around a little each night because my Garmin distance to that tree changed daily.

                        2017 Goals: for races not to be exercises in futility

                          It's best to measure with your car, because the tires keep 100% contact with the road, making for a more smooth, reliable measurement than a runner bouncing up and down.


                          Car odometers are pretty inaccurate. A GPS will typically be much more accurate. A GPS in a car may well be more accurate than a GPS on your wrist (maybe that's what you were saying?).


                          A bicycle computer (not a gps one - but one that count wheel revolutions) will be very accurate *if* you calibrate it properly.

                            If my Garmin is within .05 or so for a shorter race like a 5K (say, 3.07), I accept the course as accurate. 


                            I run the some of the same routes pretty often. Although the readings from the Garmin are usually pretty close for the same route, every so often you get a reading that is quite a way off from the usual. So, whilst they usually seem to measure the same thing, it's not always so.