[postgis] distance(geometry,geometry) function

Dave Blasby dblasby at refractions.net
Tue Jul 24 13:11:30 PDT 2001

> PROJ.4 does include a geodetic great circle distance calculation program.
> I wonder if it would be best putting off such advanced services untill
> you can build an entire
> projections library into PostGIS.  I would certainly promote PROJ.4 as
> an option.  However,
> I would assume this (building in full OGC projection support) would be a
> ways down the road
> for PostGIS.

I agree 100% - I dont want to do anything to do with projections for a
And I'm almost certainly going to integrate PROJ.4.  In fact I'll
probably steal your code since you use the WKT projection

Right now geodetic coordinates are dangerous since they represent
"non-straight-line" geometries.

I know PROJ allows one to calculate the great-circle distance between
two point, but does it calculate the point of closest approach between
two lines?


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