[mkgmap-dev] Precision circle

Mon May 25 09:56:37 BST 2009

Just a little bit of info. I made some experiments with a GPS72 with other maps (POI only, not OSM) a couple of years ago. I remember the radius of the circle precision is something like "GPS real-time in-accuracy" + "displayed level map in-accuracy". The map in-accuracy depends on the "garmin" level. If a map shows a level 24 (the most possible "accurate" level), the map precision is 3/4 meters. If the map has only levels up to 23, the precision is 6/8 meters. If the map has a maximum level of 22, precision is 10/15 meters, and so on.

Ciao, Marco.

P.S. Level 24 means using 24 bits to store coordinates (lat/lon). And so on...

--- Lun 25/5/09, Felix Hartmann <extremecarver at googlemail.com> ha scritto:

> Da: Felix Hartmann <extremecarver at googlemail.com>
> Oggetto: Re: [mkgmap-dev] Precision circle
> A: "Development list for mkgmap" <mkgmap-dev at lists.mkgmap.org.uk>
> Data: Lunedì 25 maggio 2009, 08:48
> For me on Vista HCx it's working as
> well. Once position is accurate, precision circle is very
> small.
> 
> Nop wrote:
> > 
> > Hi!
> > 
> > Ralf Kleineisel schrieb:
> >> Nop wrote:
> >> 
> >>> The discussion over at the GPS forum points
> towards a setting inside the
> >>> map, too. It seems mkgmap marks the maps as
> terribly inaccurate so the
> >>> maximum precision is an inaccuracy of 260m.
> >> 
> >> With my maps generated with mkgmap my eTrex Legend
> HCx shows the circle
> >> correctly, i.e. it disappears when the GPS
> position precision is good enough.
> > 
> > Ok, so we have 2 with the problem, one without. Let's
> try to figure out the difference.
> > 
> > Does anybody have any idea where in the map this
> setting is stored?
> > 
> > bye
> >     Nop
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> > mkgmap-dev at lists.mkgmap.org.uk
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> > 
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