[postgis-users] complete newbye

[Vinko Vrsalovic]

On Tue, Jun 22, 2004 at 06:53:30PM +0200, william wrote:
> 
> 
> Basically I'm trying to understand how things works. I couldn't find no 
> documents or drawings of  the internals of PostGis
> nor any descriptions of PgArc principles, but maybe I'm dumb and I have 
> missed these informations somewhere ?
 

AFAIU, PostGIS is a collection of functions, programmed in plpgsql 
(postgis.sql) and C (libpostgis.so), extending PostgreSQL through the
standard ways.

The enhanced spatial operators are provided through
GEOS, a C++ library (http://geos.refractions.net, libgeos.so). 

In addition to the
functions, which perform all the spatial operations on the spatial data,
PostGIS also creates two new tables per database to store
statistics about the columns with spatial information, and 
to allow projection transformations.

Also it declares a new PostgreSQL type (geometry) that
allows you to store the coordinates in OpenGIS format, required by
PostGIS, and the PostgreSQL operators to, well, operate on the 
columns with the new data type, this includes operators for the 
GiST index, so you can access spatial data relatively fast.


-- 
Vinko Vrsalovic <el[|- at -|]vinko.cl>