[postgis-users] polygonize and other geometry constructors

strk at refractions.net strk at refractions.net
Fri Jan 28 08:14:10 PST 2005

On Fri, Jan 28, 2005 at 10:00:02AM -0600, Pericles S. Nacionales wrote:
> Hi, I'm trying to make polygons out of point geometries and have a couple of 
> questions:
> 1. Does polygonize work on point geometries or just on lines?

Should work with every geometry with dimension > 0 (all but points).

> 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.

Did you feed the lwpostgis.sql script to your database ?
Or are you using some custom upgrade method ?
The calls are correct.


> 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?
> Thanks,
> 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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