UKH

Hi all,

Is there a general rule of thumb for accuracy range with Garmin GPD watches.

For example, if I do a run and it tells me I did 4.7 miles, is there a +/- % I can use to get an idea of the likely range?

PS with all due respect to those who may well come on and say "who cares, what does it matter?" The answer is that, as a data Hoover, I'm interested but broadly would just like an idea of general accuracy.

Thanks in advance

M

In reply to Rampikino:

I've got a suunto, my mate has a Garmin and they regularly differ by as much as 5%.

In reply to DaveHK:

I understand there may be some large differences between devices.

Online googling seems to suggest 1-5% error in distance as a broad rule of thumb...

In reply to Rampikino:

I think it depends on how good a satellite lock you get too - I sometimes get stray numbers (Garmin Fenix 2).

However, I run most days and my 'bread and butter' run is 8km, and it usually comes in within a few hundred metres of that (run trails so there can be a bit of variation and meandering).

I did a run today - came in at 14.2km - I've run it twice before and just looked on Strava matched runs - they came in at 14.6 and 14.4 - I'd say that's a pretty decent margin of error (~2.5%?).

In reply to Rampikino:
They're true GPS devices so they'll only ever be accurate to 10m for each sample point at best. That's not going to give you a consistent %age error. You'll just have to live with it.

The new Garmins have GLONAS as well so may be more accurate.

If you're that fussed you need to use some editing software and drag your sample points onto known points on a map.

In any case you're expecting too much from the device. Regardless of what the U.S. Military say they can do with their missiles, they don't use pure GPS.

In reply to yorkshireman:

Certainly a lot of factors

The ParkRun I do on Saturday is apparently a wheel-measured 5k. If you take this as truth and you run on pretty much the same line the whole way around then it's fair to say your GPS distances should be similar to each other and also the 5K. Naturally there will be variation.

My Garmin has measured this one at anything between 3.08 miles and 3.12. This is less than 1% difference to the claimed actual of 3.10.

In this case 5% variation seems a huge amount. Scaled up to longer distances the effect is probably lighter...?

In reply to Rampikino:

My London marathon came out at 28.7miles.

In reply to DancingOnRock:

Wow! An ultra!


I've looked at the GPS and satellite overlay and there are some definite quirks and inconsistencies so I guess I can work things out from that!

In reply to DancingOnRock:


Mine came out at 26.65 using a garmin 310xt. It got rather confused in the city in the canyons of the office blocks. But it was close. The trace is all over the place there. I would trust it to be very accurate given a reliable signal

In reply to Rampikino:

Depends quite a bit on the course and the environment.

If you run in a straight line it is more accurate than if you run a route with lots of corners and doubling back, etc

If you run in the wide open it is more accurate than if you run in the city between tall uildings, or in forests