[postgis-users] distance() for 3d points

[strk at refractions.net]

distance() is 2d only.
--strk;

On Fri, Oct 21, 2005 at 02:57:47PM -0400, Rick Schumeyer wrote:
> Does the distance() function work for 3d points, or is there a distance3d()
> function?
> 
>  
> 
> My quick tests show that distance() seems to use only the first two
> dimensions and ignore the third:
> 
>  
> 
> select AddGeometryColumn('t2','geom',-1,'POINT', 3);
> 
>  
> 
> insert into t2 (name, geom) values ('p1',GeomFromEWKT('POINT(0 0 0)'));
> 
> insert into t2 (name, geom) values ('p2',GeomFromEWKT('POINT(0 0 1)'));
> 
> insert into t2 (name, geom) values ('p3',GeomFromEWKT('POINT(0 1 1)'));
> 
> insert into t2 (name, geom) values ('p4',GeomFromEWKT('POINT(1 1 1)'));
> 
>  
> 
> select distance( geom ,GeomFromEWKT('POINT(0 0 0)')) from t2;
> 
>  
> 
>     distance     
> 
> -----------------
> 
>                0
> 
>                0
> 
>                1
> 
>  1.4142135623731
> 
>  
> 

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