Garmin 305 Under-measuring distances?

Hello all,

Sorry for yet another Garmin thread but I've had a quick look if I can find anything re this problem on here and I can't. Basically I think my Garmin is slightly under-measuring the distances I run.

In my last 4 training runs I've downloaded the info into Sport Tracks and on each occasion the distance Sport Tracks says I've covered is about 0.25 of a mile further than my Garmin says. Then on Saturday I ran a 10 mile race (exactly 10 miles on SportTracks too) but again my Garmin says 9.80 miles.

Anyone had anything similar and if so is there an easy remedy? It's not a massive problem really, but one I'd like to sort out even if it's just to view my mile splits accurately.

Any help gratefully received!

ST always says slightly more that my Garmin. I think  it has a slightly different algorithm for working out the distance/error from the raw data contained in the garmin. I have wondered which was better but found no satisfactory answers although from waht you say ST sounds more accurate (Assumign the course was). I am sticking with the pessimisitc Garmin calcs because it means things are simple. I am only looking at one set of figures and means I wont get any nasty surprises when I realise how slow I am in a race!

OK cheers for that - makes sense!! It's not a problem as such really - more just a little bit annoying I guess, but only cos I usually pour over my stats and mile splits afterwards and try to work out where I've lost time.

It's only really started doing it in the last 2 weeks or so too (seemingly) - there was often a 0.05 or so difference between Garmin and SportTracks but that's by the by really - but when I've been getting differences of 0.3 of a mile I had wondered if something was maybe wrong.

Not to worry - I think I'll just crack on and adopt your strategy - sounds good advice!