Garmin 500 satellite drift

dabber

I've recently noticed that I'm getting satellite drift on my Garmin 500 on quite a regular basis.

It seems to happen most often when I go up and down the same bit of road several times. As an example, today I did a couple of hill repeats and noticed, on Strava, that there were some segments missing. These were all in the area of the hill repeats and zooming in I could see that my ride had drifted quite a bit.
I have, occasionally, been able to correct this using the Raceshape SNAP tool but this didn't seem to work for me today.

The road was a bit overhung by trees but it wasn't a narrow lane completely shielded by branches and leaves.

I'm running the G500 on Software Version 3.30 and GPS 2.60

Is this pretty much normal or is my G500 likely to be faulty?

antfly

Try switching it on and leaving it outside for half an hour, it worked for me when my 800 started losing satellites.

dabber

It finds the satellites OK before I start my rides. In the case today it was about a third of the way around that it started to play up. It was really just in the hill repeat section and was fine for the first and last thirds of the ride.

antfly

Yes, mine was the same. It's worth a try anyway, it won't do any harm.

dabber

Thanks... I'll give it a try... as you say, nothing to lose.

jimwin

If you go to the satellite page, you can see how many satellites are being received. You need at least 3 to get a fix, more will make it more accurate.
BTW - I assume the 500 does have a satellite page (my eTrex Legend HCx does)

dabber

Interesting jimwin. I hadn't really looked at this aspect in any detail before.

I just did a quick test in my front garden (The Garmin 500 does have a satellite page)...

The number of satellites identified ranged between 6 to 7 with varying levels of signal (high to low).
The indicated accuracy varied between around 35 feet to 70 feet.... fluctuating all the time.

These readings will obviously vary throughout the ride. I'm presuming that during the section of the ride where the recorded ride was way off course these reading would have been much degraded.

I guess my question is whether this is normal and something I have to live with or whether my 500 is not performing well and I should speak to Garmin (still under warranty).

I noticed that when I started the test it took a little while for the readings to start to stabilise and I will ensure that I turn on as much in advance of starting my ride as is practical but whether that will make any difference once into the ride I'm not so sure.

pirnie

My edge 500 does have similar drift occasionally and I'd guess the tree cover isn't helping... This isn't a solution as such but it does let you correct the ride once you get home if it's drifted off the road so you can get those all important segment times

http://strava-tools.raceshape.com/snap/

dabber

Thanks... you'll see that I made mention of SNAP in my original post.

I have had some success with it but not always.
Yesterday I couldn't get it to resolve the problem at all. It was complicated by the fact that the off course section was ridden a couple of times in both directions.
If anyone has any good tips on using SNAP I'd appreciate the input. :?

pirnie

Ahh, sorry. Clearly didn't read your original post fully! :oops:

timothyw

To be honest, this is rather a fact of life if you're riding anywhere tree or building lined - the GPS signal is going to be less clear and so more likely to be inaccurate, seems that you've just been unlucky that SNAP hasn't fixed the track for you - there might be another tool somewhere that will work.

You can try leaving it static outside for a long time to see if it somehow recalibrates itself, but I suspect that anytime that you are carrying out repeats you'll notice this sort of thing when you zoom in.

If it really bothers you, consider selling your 500 and getting a 510 - they can use a combination of GPS and GLONASS and have been reviewed to give a much more accurate fix.

dabber

OK, thanks... it sounds like this is a common occurrence and not worth querying with Garmin. I've only had the G500 since the beginning of the year so I don't plan to upgrade it in the near future.

I've had a search around but not found an alternative to the SNAP tool but I'd be interested if anyone knows of anything. I find SNAP a bit awkward to work with but I have managed to fix the odd thing in the past.