[OSM-talk] Garmin eTrex Vista Hcx

John F. Eldredge john at jfeldredge.com
Sat Oct 31 17:30:44 GMT 2009


The GPS in my car is a Garmin (I don't recall the exact model at the moment).  It appears to be much more accurate when the car is in motion than when the car is stationary.  If I power the GPS up with the car stationary, the location given can be inaccurate by 100 meters or more.  Once the car starts to move, the GPS can locate the car within 3 or 4 meters.

-- 
John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria

-----Original Message-----
From: Konrad Skeri <konrad at skeri.com>
Date: Sat, 31 Oct 2009 18:08:58 
To: <talk at openstreetmap.org>
Subject: Re: [OSM-talk] Garmin eTrex Vista Hcx

No matter how good signal you have there is always a chance that the
given position is wrong without limitations. So when talking of a
satellite error of +-5 meters that actually means that with 95%
probability the error is +-5 meters. The possible error in the last 5%
is limitless, and my guess is that you were hitting that last 5%.
(Last week my GPS, which is not a Garmin, placed me on the north pole
+-20 meters for 5 seconds before returning me to a more sane position.
The probability such misreading to appear should be very, very low.)
As Mike wrote, this is more likely to happen under trees, near large
buildings or other obstacles. If you return a third time you should
get a position that is very close to one of the first two.

Konrad

2009/10/31 Shalabh <shalabh.w at gmail.com>:
>[...]
>
> 3. I parked my car near a village a day before, marked a waypoint. The
> satellite error was at +- 5metres. Today morning, I came back and marked
> another waypoint. This time the error was +-4 metres but this waypoint is
> 150 metres off the earlier one. The car keys were with me and I can vouch
> that my car does not move on its own. :)
>
>[...]

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