[postgis-users] Checking Road Network Topology
smille12 at harris.com
Thu Jan 22 13:01:10 PST 2015
I think I am ensuring the geometries are both projected to 32648 (zone 48N UTM). The tolerance being sent to topology.toTopoGeom is 1.0, presumably this is in meters. I will try the next run with 0.0000001 which is appropriate if the tolerance is being applied to 4326 coordinates for some reason. A tolerance of 1.0 degree would certainly explain why every line would be reduced to a point or convolute the input.
I have not gotten around to using LIMIT and OFFSET as you suggested. I keep thinking I have overlooked something important.
Here is the code I am running now.
-- Drop the existing topology
-- Create a new one
SELECT topology.CreateTopology('roads_topo',32648, 0.000001, true);
-- Add the new topo_shape column
select topology.AddTopoGeometryColumn('roads_topo', 'fgcm', 'transportationgroundcrv', 'topo_shape', 'LINESTRING');
-- Encapsulate the UPDATE inside code that checks for errors
DO $$DECLARE r record;
FOR r IN SELECT objectid, f_code, shape, topo_shape FROM transportationgroundcrv loop
UPDATE transportationgroundcrv SET topo_shape = topology.toTopoGeom(ST_Transform((ST_SetSRID(shape,4326)),32648), 'roads_topo', 1, 1.0);
WHEN OTHERS THEN
RAISE WARNING 'Loading of record % failed: % %', r.objectid, SQLSTATE, SQLERRM;
Select * from ValidateTopology('roads_topo');
Let me know if you see something obvious.
From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf Of Sandro Santilli
Sent: Thursday, January 22, 2015 3:53 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Checking Road Network Topology
On Thu, Jan 22, 2015 at 04:13:44PM +0100, toni hernández wrote:
> I had the same issue when working with geometries using srid=4326 .
> I was also following the same link
> road-networks.html) Then I tried with some projected geometries (units
> = meters) and the problem was gone. I am not sure why. Maybe it was
> just a coincidence.
Can it be you're specifying a too large of a precision for your topologies in srid=4326 ?
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