[postgis] Re: PostGIS query

[Dave Blasby]

> I'm interested in using PostgreSQL as a back end spatial RDBMS.
> 
> Having just stumbled across PostGIS, I'm wondering what it offers above
> the spatial functionality available with v7.1 of PosgreSQL?

I suggest that you visit http://postgis.refractions.net for more
details.  Release 0.5 is imminent (hopefully tommorrow) and has many
more features than whats currently documented in 0.2.

But, back to your question,

1. Types
	+ PostgreSQL types are 2d, PostGIS are 2d and 3d.
	+ PostgreSQL only supports point, line, and very simple polygons
	+ PostGIS support the OpenGIS WKT types, and their 3d equivalents
		POINT, LINESTRING, POLYGON, GEOMETRYCOLLECTION,
		MULTIPOINT, MULTILINESTRING, MULTIPOLYGON
	+ PostGIS polygons support holes
	
	The major differences is that the PostGIS geometry type can be either a
POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON or
a combination (thats what a GEOMETRYCOLLECTION is).  These types more
accurately reflect spatial information needs than the basic types in
postgreSQL.

2. Indexing
	+ PostGIS supports full indexing of the geometry types.
	+ The PostgreSQL types, I believe, do not all support indexing.

3. Binary Access
	+ PostGIS supports endian-aware binary access (OpenGIS Well Known
Binary)

4. Functionality
	+ PostGIS is trying to support most of the functionality described in
the OpenGIS specification (http://opengis.org/techno/specs.htm)

In summary, the two biggest differences are  (1) PostGIS supports a much
richer set of geometry types and (2) is actively being developed using
the OpenGIS spec as a guide.


Does anyone else have anything to add or comment?
dave

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