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I have a garmin 500, which tracks accurately almost all of the time. However, on my return commute, it goes haywire. I head west along Prices St, then A8. Does anyone else use a garmin on this route between 6PM and 8PM and have any issues ? It gets a gps fix ok, but then goes off route. It only happens on my rtn commute and happens to a greater or lesser extent each time.
edit: it seems to crop the image a bit. http://www.flickr.com/photos/24775321@N02/13092695955/
I used to cycle in broadly the same direction through the West End and Coates along A8 to the Zoo. My Garmin Edge 200 recorded that very accuratley.
Looks like you've had a few gins with that trace!
Hey SG37409,i am not a garmin user, but that map trail looks suspiciously like the tramworks traffic diversion away from shandwick place,
so(guessing wildly) maybe Garmin havent updated something yet??
Radgeworks
I've seen wandering gps tracks occasionally but nothing as bad as that! Presume it's got a clear view of sky etc.
I've got my 500 with me today. If I get away on time I'll take a wee detour on the way home (such a hardship in this weather) to see if I can reproduce the issue ...
Doesn't matter which GPS you use, the Garmin and others use the CSR/SiRF chipsets. Try it on your smart phone?
Doesn't matter which GPS you use, the Garmin and others use the CSR/SiRF chipsets. Try it on your smart phone?
GPS signals can bounce off large buildings and sometimes be received in place of the 'direct' signal, but the error caused by this is pretty much the extra distance the signal travels to usually limited to a few 10s of meters. Long shot, but maybe the buildings round there are reflecting it all over the place.
It looks like the error is a big jump south for a period, it it the same every time? Is the north/south jump instantaneous?
My guess is that you're cycling too fast and relativity is rearing it's ugly head. Slow down.
I tried to reply earlier but received another 403 error.
I suspect that the Garmin's internal map knows about the tram diversion routes and is trying to lay down a breadcrumb track using the 'follow road' option, but that also depends on the route calculation vehicle settings. In my GPSMap 60CSx I've turned that option off so that it tracks where I actually go.
Interesting, hadnt considered that maps may have the diversions in it. Not sure its this though: I also go widly off-route in corstorphine, and out towards ingliston. Its random, but so far as when it happens, seems only to happen on my return commute.
Another example: http://www.strava.com/activities/113122819
Puzzling. Its a reconditioned model from garmin though think this is not a factor as other rides are fine.
Thanks for replies / suggestions.
"I suspect that the Garmin's internal map knows about the tram diversion routes"
Garmin 500 doesn't have an internal map as such. They can do odd things - perhaps a good idea to update the software (there is a new version out just now)? I once had an apparent mighty quick trip to Canada and back from Morven.
FYI…. My commute to work that morning. (its not always as spot on as this but usually pretty damn accurate)
Pretty much said above by others... check it's not set to try to place you on a road (lots of devices have this setting I believe - makes them useful for drivers). Check how often it records a point. Look to see what happens near other tall buildings - the error occurs at the point you move from one distinct environment to a very different one (tall buildings on one side, nothing on the other to tall buildings both sides). Tall buildings and trees with heavy leaf cover can knock a gps device guess at a location off by quite some distance.
If it's the same place and the same time, I'd suspect satellite coverage over anything else. Maybe you get an initial fix on two or three satellites but at this spot because of buildings and the position of satellites, you're down to one. My understanding is that from each satellite the GPS can place you somewhere in a circle on the surface of the earth. It's gets its most precise location by finding the intersection of all the satellite circles you could be in. The more satellites you're tracking, the smaller the intersection and the more precise your location. If you're down to one satellite you can be anywhere on a circle so where the GPS puts you depends on the size of the circle.
http://www.pocketgpsworld.com/howgpsworks.php
For what it's worth, my Garmin 500 always takes ages to get a fix on my way home. Some nights I can leave work in Queen Street and be half way to the red bridge before it locks onto the satellites.
@insto That's pretty much right.
There's a lot got to happen before you get a 'lock'.
Before it can do that it also needs to get the date/time confirmed by multiple sats.
Once it knows the time, it can work out if it knows the sat position data. If the device has been off for a while it needs new position info for each sat it is talking to which can take a couple of minutes - this is the main delay.
If the initial comms gets interrupted, for example because you started travelling and a building got in the way, it's got to start the conversation over.
I switch my Garmin 500 on as I walk to my bike, and it's usually got a lock by the time I stop faffing and start riding about 3 mins later.
GPS signal is very weak. Regarding the missing airliner in the news, I find it frustrating that the press keep suggesting that the 'black boxes' should be able to get their position from GPS and transmit it. That's not going to work under 1 meter of water, never mind 1000 meters.
I think its most likely satellite coverage than anything else also. Interesting that other garminers also notice it can take for ages to get a decent fix at knocking off time. It is surprising how off-route it goes at times, even after getting a fix. I thought it needed min 3 sats to get the fix which would be accurate enough. The inaccuracies are all over the place, not just near high buildings which gives me a doubt on this but the fact that its at this time in this place strongly suggests its environmental only.
I have a fancy dancy etrex 30 which i'm gonna try on this trip tomorrow. It also uses the russian satellite system, will post a comparison. (I don't know why i didn't think on this before, its just dawned on me…. !)
Hi,
I had similar problems (although not as wild as yours) with my garmin 500 too.
Things improved quite a bit when I added a speed and cadence sensor
Tonight allowed my garmin 500 to get fix on satellite. Just switched on my etrex 30 and put in pocket. A lot of the time the garmin 500 was a lot more accurate than this, but always the etrex was a load more accurate.
Garmin 500
Etrex 30 using GLONAS
I guess I could try setting my etrex 30 to non-glonas.
I'm beginning to think this is evidence of an actual fault with your 500. If it's within any sort of warranty, I'd certainly continue to collect the dual recordings as you have above, and revert to the seller.
It shouldn't do that if you're letting it get a fix before setting off, etc.
+1. There is no way that your 500 should be that terrible along that stretch, which I've travelled along countless times with both an Edge 800 and a FR910xt. They always track like your bottom trace.
I find my 800 picks up satellites at startup extremely quickly in comparison to the FR910xt - typically within 5 seconds. I believe the 500 should be just as quick. Therefore, as @Snowy says, I'd be taking it back if it's less than 2 years old.
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