[postgis-users] polygonize and other geometry constructors

Pericles S. Nacionales nacional at cbs.umn.edu
Fri Jan 28 08:00:02 PST 2005

Hi, I'm trying to make polygons out of point geometries and have a couple of 

1. Does polygonize work on point geometries or just on lines?

2. How does the MakeLine and LineFromMultiPoint work?  I tried both on my 
point geoms and both returns:
ERROR:  function linefrommultipoint(geometry) does not exist
HINT:  No function matches the given name and argument types. You may need to 
add explicit type casts.

I have PostGIS 1.0rc2 compiled with GEOS 2.1.1.   I can use the Collect 
function to create mulipoint geoms from point geoms but the other functions 
don't work for me.  What am I doing wrong?

Here's are the statements I used for #2: 
SELECT makeline(the_geom) FROM data WHERE squirrelid=702
SELECT linefrommultipoint(collect(the_geom)) FROM data WHERE squirrelid=702

While I'm at it, I might as well ask if there are any wildlife/population 
ecology types out there who use PostGIS?  And if so, have you used PostGIS to 
do homerange analysis stuff?

Perry Nacionales

Pericles S. Nacionales

Dept. of Ecology, Evolution, and Behavior
University of Minnesota
work: 612 624 6713
e-mail: nacional at cbs.umn.edu

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