[postgis-users] Postgis Simplify

[Christo Du Preez]

SELECT Simplify(the_geom, 80), the_geom

Produces:

SRID=-1;MULTIPOLYGON(((-3.40056774339641e-063
-4.38828018269539e+033,1.29793581702902e-099
-4.71199750007451e+156,2.14675261499012e-179
6.45280524121602e-108,3.18999891494113e+087
-2.9437206290273e+237,-2.11301423329521e+231
-2.41070996669296e-010,-4.80307 (..)

SRID=-1;MULTIPOLYGON(((18.441127 -33.919793,18.442126
-33.91885,18.442537 -33.918462,18.442729 -33.918603,18.442464
-33.918852,18.441329 -33.919914,18.442208 -33.92056,18.44628
-33.920351,18.44426 -33.91886,18.443569 -33.91835,18.444617
-33.917363,18.4404 (..)

With 85000 points I presumed that the IsSimple method would return
False, but I was wrong. IsSimple returns True.

It does say in the documentation to test IsSimple otherwise the
Simplify method might loose the geometries simplicity. I take it, this
is what they meant.

So my question, what do I do to simplify the geometry eg. reduce the
number of points for displaying my maps on different scales?