[postgis] distance(geometry,geometry) function

Timothy H. Keitt tklistaddr at keittlab.bio.sunysb.edu
Tue Jul 24 16:12:22 PDT 2001

Dave Blasby wrote:

>I've actually been thinking of making types like GEOMETRY_POINT and 
>GEOMETRY_MULTIPOLYGON available (leaving the current GEOMETRY as
>GEOMETRY_GENERIC).  It just means a whole lot of extra functions for
>handling all the operators and indexing.  I think I've come up with a

I like really compact, orthogonal interfaces, so don't add a bunch of 
stuff on my account! ;-)  That said, I really like strongly-types 
languages, so that is probably why I was thinking about seperating the 
geometry types as different sql types, e.g., "select cast((10, 
12)::geodeticPoint as albersEqualArea, ...)" or something.

>plan that will make this much easier than writing a HUGE number of
>support functions.  I just need the time to do it. There's been some
>dissention in the ranks arguing that it doesnt actually give you much
>extra than whats already there.

They may be right.

>As far as having more complex functions, since openGIS defines a
>geometrycollection type, all those functions still have to provided. 
>Besides, its still legal to say distance(polygon, line) so all the
>support functions need to be written anyways.  Once they're written its
>trivial to write the generic case (just pass smaller parts off to the
>support functions).
>The PostGIS geometry type is different from the standard PostgreSQL
>geometry types in that (1) we support 3D (2) indexing on all types (3)
>more advanced geometries (like polygons with holes) (4) collection-type
>geometries(multi* and geometrycollection) and (5) no size limit.
This is great.  As I said before, I'm really excited about postgis.


Timothy H. Keitt
Department of Ecology and Evolution
State University of New York at Stony Brook
Stony Brook, New York 11794 USA
Phone: 631-632-1101, FAX: 631-632-7626

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