[postgis-users] Does ST_AsText truncate or round

[Paragon Corporation]

Slight clarification about what I am trying to solve.

After edits I am coming back with lines that used to be intersecting no
longer intersecting and that still have the same AsText representation.

My hope is to reduce the precision of my geometry in the database so the
edits don't break the topology of my lines by doing something like this


Update sometable
	SET the_geom = ST_SetSRID(ST_AsText(the_geom), mysrid)


But I fear that if AsText is doing a rounding rather than a truncation, that
I run the risk of breaking things that used to intersect.  I am more
concerned about under intersecting than over intersecting.  Although I
probably haven't thought this out enough so maybe it's a non-issue.

Thanks,
Regina

 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Paragon
Corporation
Sent: Friday, May 16, 2008 12:01 AM
To: 'PostGIS Users Discussion'
Subject: [postgis-users] Does ST_AsText truncate or round

Hopefully this is a simple question.  I know that ST_AsText returns a
geometry that is not necessarily as prescise as what is actually stored in
the geometry field.  I have an editor that relies on WKT representation.

Anyrate just wanted to know if the ST_AsText does a rounding of the points
or it does a truncation of the points.  Also would be nice to know if I
could control the precision of this since I will need to truncate my actual
geometry accordingly so that both are in agreement.

Thanks,
Regina


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