[Proj] Any access to geodetic functions ??

Frank Warmerdam warmerdam at pobox.com
Wed Nov 12 10:50:37 EST 2008

Benoît Andrieu wrote:
> Thank you so much for your answer, Frank.
> So, this leads to some questions (that are somehow related...) :
> - how are computed distance calculation between two points by softwares 
> like Postgis for example ?


I'm not sure.

> - is the best way to compute distance calculation to use UTM systems ? I 
> have to compute distances that could be very long (hundreds of 
> kilometers), strong accuracy is not required but I don't want to have 
> more than 1% accuracy error.

Other have addressed this, but generally this is not a very good approach
except for fairly local areas.

> - in what way are those functions distinct from the proj4 ? Am I wrong 
> to use them ? Are there others functions in proj4 that would allow me to 
> do the same things that I can do with those functions (distance 
> calculation between two points and point positionning given initial 
> point, distance and azimuth) ?

The functions are not a core part of PROJ.4 as I understand it.  They aren't
normally in the library - just linked with the geod command line program.

I'm not opposed to treating them as a core capability but I do think some
consideration should be given to the API before this would occur.  Ideally
this would be something someone else than me might take on (possibly with
some advice from me).

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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