235 v 310XT different distances on the same route?

Looking at the time difference isn't very helpful because the same distance differential will cause a different time differential at different paces. More than likely the measured difference was in the hundredths of a kilometer range and well within the normal margin of error for consumer level GPS devices.

Even the same device can measure the same route differently on 2 separate runs simply due to how many satellites it's seeing at the time. If you did the same experiment for several runs and stopping both watches when the second one hit 6km the difference in distance would probably average out to less than 50 meters which is a more than acceptable for the purpose. In most people's opinion at least.

GLONASS can help with trail routes even if there isn't very much canopy since signal strength isn't reliant on just what is directly above you but also the angle of sky sight on the sides, so more signals the better.

Looking at the time difference isn't very helpful because the same distance differential will cause a different time differential at different paces. More than likely the measured difference was in the hundredths of a kilometer range and well within the normal margin of error for consumer level GPS devices.

Even the same device can measure the same route differently on 2 separate runs simply due to how many satellites it's seeing at the time. If you did the same experiment for several runs and stopping both watches when the second one hit 6km the difference in distance would probably average out to less than 50 meters which is a more than acceptable for the purpose. In most people's opinion at least.

GLONASS can help with trail routes even if there isn't very much canopy since signal strength isn't reliant on just what is directly above you but also the angle of sky sight on the sides, so more signals the better.

Yes I think it is around 50 mtrs ish. Thing is it's then showing faster lap times on the 310 than the 235 which is annoying. We strive to run longer and faster and then the watch tricks you! Every run the 310 is faster than the 235.
Cheers for the reply.

there's so many things it could be.

FWIW I find the 235 slightly UNDERestimates distance with glonass off.

you can try a few things

1 use a smartphone+app as a 3rd device. that might help determine which one is 'out'
2 ensure the devices all have a full gps fix. sync and then leave out in the open for >15 minutes and RECORDING a run
3. glonass SHOULD improve accuracy under tree cover.

or

4. just think to yourself 'does it really matter?' :-)

Any 2 GPS devices worn on the same run will typically show slightly different distances. That is just the nature of GPS which is not an exact way of measuring something.

That said I have tended to notice the newer devices like the 235 do sometimes come up slightly shorter than older ones like the 310 although when I compared the GPS tracks could see that the 310 was more "wavy" more often in the circuit I did a similar experiment.

Perhaps you can post the 2 GC links so we can examine this.

Which one do you believe is more accurate and why?

Cheers all.

I guess it's not the end of the world but if I'm running with my wife and her watch is bleeping 5-8 seconds earlier than mine per laps and then she's finishing our set distance runs at different times it's off putting to the man who likes order without chaos. ( I don't want her weekly miles being more than mine lol)
Think I'll try the running with the phone on too just to compare 3 devices. Can anyone recommend an app to use on the phone as I never run with my phone.

Cheers.

Cheers all.

I guess it's not the end of the world but if I'm running with my wife and her watch is bleeping 5-8 seconds earlier than mine per laps and then she's finishing our set distance runs at different times it's off putting to the man who likes order without chaos.

Cheers.

1. turn one of the beepers off
2. press the manual lap when hers beeps. that will reset the current lap count to zero. if it is a prob at the start of the run then this might make it ok for the rest of the run with just one manual press. this may also help you understand through the run if certain environmental factors (trees) are causing the problem.
3. just walk around a bit with your watch recording and pretend to her you ran it (she may already be doing that to psyche you out ;-) ). that should work for beating her total mileage.

Which one do you believe is more accurate and why?

Not geared to this poster at all but...

In general what I've noticed reading these forums on and off for the last few years is that people tend to think that whatever they used first is more accurate than what they've recently bought. Probably for the simple fact that the distance that they're used to getting from the other device is, psychologically, their baseline.

If they've been using a phone app for a year and their usual 5k run always ends within 10 meters of a given road sign and then buy a new Garmin which tells them that 5k ends at a lamp post 20 meters farther up or down the road they start to question why this supposed better solution is making them run either less or more than perviously to get credit for the same distance.

Some get angry about the new device being "crap" because it doesn't give the exact same readings they're used to, others learn more about how GPS works and accept the differences.

good point, I agree

CW

All excellent points. Thanks for the replies.

Mine seem pretty good on races

I did 4 races this season (I run to run and race only for a change of scenery).

1 10k and 3 halfs
10k reported 6.23
Halfs were 13.23 (trail run heavy tree cover lots of the time and the organizer said was 13.35)
13.14 (point to point race mostly pretty straight with only a few major turns)
13.21 (lots of turns and no way I had a perfect line)

I'm happy with mine, don't think it could be much better. The last half was my wife's first and I paced her. She was using Endomondo on an iPhone 6+ and she was always hitting miles before me (also on training runs leading up to it). By the end she was 0.3 longer but I was also much closer to the actual length and still a touch long.

My most often run 5 mile route I hit miles almost exactly in the same spot everyday and thus I finish 5 miles within +/-20 feet total at the end. When I have also used my iPhone it will be dead on some days and long others. For the brief time I had a Fenix 3 when it came out it would have been closer to 4.85-4.90.