[gdal-dev] Re: OGRGeometry Distance

Christopher Barker Chris.Barker at noaa.gov
Thu Sep 24 12:51:35 EDT 2009

Yilmaz Arslanoglu wrote:
>>> you need to be clear by what you mean here: I suspect you mean:
>>> "The shortest distance between two points following the surface of the
>>> earth"
> Yes Chris, you are right. Actually my purpose is to make a bathymetric
> prediction of a given position, with the help of the contours and sounding
> points at hand. I just thought that it would be a better idea to take shortest
> distances in calculations (maybe the Kriging) rather than using pure lat-lon
> values. So does it make sense to use the geodesic distances for the
> closeness criteria?

I don't think so -- at that scale, it really won't make much difference 
-- probably far less than the accuracy you need, so I don't think it's 
worth the computational overhead.

If you want to do a little better than simple lat-long, do the 
calculations in projected coordinates, using a appropriate projection.

Do be careful about Kriging -- Kriging assumes a certain smoothness to 
the data -- it won't capture cliffs well. though no matter how you slice 
it, if you don't have a sounding there, you're not going to get it perfect.


Christopher Barker, Ph.D.

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Chris.Barker at noaa.gov

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