[Talk-ca] Primacy of GPS Traces (was Re: Internal CanVecconflicts)

[Daniel Begin]

Agreed about GPS behaviour,

 

and do not take for grant your 3m accuracy. I got 3m accuracy measurement on
my GPSmap 60CSX but a much larger differences looking at my traces, with the
same device, the same track, same day, but under different meteorological
condition.  Multiple tracks are always better.

 

Daniel

 

  _____  

From: Pierre Béland [mailto:infosbelas-gps at yahoo.fr] 
Sent: November-15-12 12:29
To: Tom Taylor; talk-ca at openstreetmap.org
Subject: Re: [Talk-ca] Primacy of GPS Traces (was Re: Internal
CanVecconflicts)

 

Tom 

I have a Garmin Etrex HCX.  I had the opportunity to compare my results
while hiking with a  friend wich has a Garmin GPSMAP 62. The antennas seems
to make the difference, especially when there is a coverage in forests.  

Even with the same brand you may notice differences. When opening the GPS,
it is important to give it at least 5 minutes to finish is procedure of
initialization. And it is worse if you move to an other continent. It takes
more time to negociate with satellites and control precisely your position.
I had a nice experience this summer in south Africa. We had seven Etrex
arriving from Indonesia and Canada.  It took ten minutes to see all of them
coming to a three meters precision. And, they were not adjusting all at the
same speed.

I see that you already uploaded a trace. You simply use this as background
to trace in editor such as JOSM. If you trace from this trace, you simply
add source=GPS. This can be added to the Changeset instead of each object
you trace.

 

Pierre 

  _____  

De : Tom Taylor <tom.taylor.stds at gmail.com>
À : Harald Kliems <kliems at gmail.com> 
Cc : talk-ca at openstreetmap.org 
Envoyé le : Jeudi 15 novembre 2012 8h38
Objet : [Talk-ca] Primacy of GPS Traces (was Re: Internal CanVec conflicts)


As a geocacher, I'm unhappily aware that different brands of GPS give
different results, with differences in the order of 10 meters for an
individual point. I suppose a track should be better, since there is an
internal consistency check, though not if the difference is due to systemic
causes. As it happens, in this case I had my own GPS trace to work with, and
it aligned reasonably well with the Bing image of the path I was following.

One thing I'm not sure of: were my GPS traces uploaded with the edits, or
did I have to do something special to upload them?

On 15/11/2012 8:20 AM, Harald Kliems wrote:
> Hi Tom:
> welcome to OSM and congratulations on your first edits! Yes, it sounds
> like you did the right thing. One thing to look out for: Bing images
> are not always aligned 100% -- they can be offset by several meters.
> Usually this is not a problem but if there are any GPS traces
> available in your area you (most likely to be found along major roads)
> you can use those to make sure that the imagery is not off. In JOSM
> you get the GPS traces by checking the "Raw GPS data" box in the
> Download window.
> Happy editing,
>  Harald.
> 
...

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