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[mkgmap-dev] Polygons deformed [Antwort]

From GerdP gpetermann_muenchen at hotmail.com on Mon Dec 24 08:35:33 GMT 2012

Frank Stinner wrote
> The problem is the Garmin-Data-Format.
> Garmin use only 24 Bit for longitude/latitude. This is for the highest 
> zoom. If you reduce the zoom, then use garmin internaly only 23, 22, ... 
> Bit.
> The biggest number with 24 Bit is 16.777.215. Use this for 360°. From this 
> it follows that 360°/16.777.215 is the minimal distance. What means that 
> for example for the equator? 360° stands for around 40.075 km 
> circumference of the earth. The minimal distance is for a latitude of 0° 
> around 2,4m! For higher latitude it is of course higher.
> I think, there is no way. 24 Bit for longitude/latitude is to less. But 
> more Bits are more memory consumption and bigger maps.
> See also on my web-page "Linien- und Polygonvereinfachung" 
> http://technik.stinnerweb.de/Gps/garmin1.html. It is in german, but the 
> pictures are language-independed ;)

I assume this problem will "disappear" when cheap hardware is able to handle 
more details, means, Garmin will sell new hardware with new software and new
formats or everything will be done just in time using online data.


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