[PD] kml files

Mathieu Bouchard matju at artengine.ca
Thu Dec 13 18:38:30 CET 2007

On Thu, 13 Dec 2007, Miller Puckette wrote:

> If I'm doing it right, single precision float should be able to represent
> latitude and longitude to within about two meters.

longitude has to be from -180 to 180. The epsilon is then the previous 
power of two divided by 2^23. In metres this is 0.61 metre near equator. 
This is the worst case. For latitude the precision is twice better than 
longitude at equator. In northern europe and in alaska, the longitude 
precision is the same as the latitude precision.

It's twice more precise to use signed values than unsigned values, which 
is why I wouldn't use longitudes from 0 to 360.

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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada

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