How accurate is my Garmin? (Read 2184 times)

I often convert my Garmin data (using this site) and upload it to mapmyrun.com (here are my courses.) Sometimes, I convert the Garmin data to display in Google Earth. In either case, I typically see jags in the Garmin course where the tracking was not accurate. Its usually due to tall buildings or bridges. Check the map for my 'lower manhattan' run for an extreme example of this. Also, my Baltimore Marathon Garmin course shows some big variations around mile 6. Urban canyons were probably not the cause in your Rehohoth Marathon, but if you transfer your Garmin data to a mapping site, you might see where it went off course.

We recently had a discussion of this topic here: http://www.runningahead.com/forums/topic/246f275e5a6a4ddcb3b2ec7b7c9145bd Your Garmin is very accurate. None of us run the exact measurement line of the course. The two factors add up to the difference in length recorded. You can argue which is the greater cause, GPS or runner. Good luck with that.

I saw a lot of Rehoboth runners not running the tangents -- which means they were running further than the measured course (in all probability).

Did your 5K go under anything that could have obstructed the Garmin? In my first half, I lost signal while running on a bridge, so my mileage was off even though the course was accurate.

Was it locked on to the satellites?

as perfessor said you probably weren't locked on yet especially given the 20 mile drive as it probably took it a little more time to autolocate. You can go into screens that show the number of sats in the mix and estimated accuracy(static). Static accuracy should be sub meter (at best) with a waas based unit like this. the 205's and 305's have that sirf chipset to minimize loss of signal due to trees , bldgs, mtns etc.. If you have a clear sky view on the race course you are gonna be dang close. The gps we use on our farm equip on a daily basis has pass to pass accuracy of 4 inches with a $1600/ YR subscription to a proprietary correction (John Deere sf2) but its a little big to strap on your wrist.

i run from the same location for about half my runs and it never takes long to locate. the satellite was locked on -- i didn't lose any of my actual run (i think i did run a little under 7 miles), it just added 25 minutes of non-running. And I didn't turn it on until i got to the track anyway. The most likely story, I've decided upon much deep reflection, is that the 25 minutes were there from before the run (maybe I'd left it on the last time I pulled it out to enter my data? and accidently hit start while it was sitting still on my desk?) and i didn't clear it before this run. And I think I should probably spend less time obsessing about the numbers on that damn screen! And thanks for the tip on the better GPS -- given that i just saw in a recent race photo what a dork i look like with my giant 205 strapped to my wrist, i think i shouldn't consider even larger versions : )