PostGIS ERROR: getPoint4d_p: point offset out of range

Question

I have a set of streets (LINESTRING) in a PostGIS 9.1 PostGIS 2.1 database.

I need to obtain points from the lines, on the right and on the left of the street.

I offset the lines with:

   ST_OffsetCurve(the_geom, 30)

then I try to get the points:

   (ST_DumpPoints(ST_Segmentize(the_geom, 20))).geom

when i get the error:

    ERROR:  getPoint4d_p: point offset out of range

Any one can replicate the behaviour ?

Answer 1

Mihai, I was able to replicate the error with this simple statement:

SELECT ST_Segmentize('LINESTRING EMPTY'::geometry, 10);

and I was able to also replicate the error with your rpoints edit. I created a ticket on http://trac.osgeo.org/postgis/ticket/2712 for this. Feel free to add comments to that ticket.

In looking at the dataset you have, as expected in the rstreets it has a LINESTRING EMPTY as one of the rows which I think is triggering this error.

How you ended up with a LINESTRING EMPTY is from the ST_OffSetCurve call, which I think is a bug in GEOS.

  SELECT ST_AsText(ST_OffsetCurve('LINESTRING(1116773.8702957 7172132.24526899,1116768.15226771 7172128.54354244,1116752.61206679 7172126.30820484,1116742.74915991 7172090.05035972,1116746.60081429 7172083.8179674,1116759.05746531 7172082.54875741,1116767.82944119 7172087.37933384,1116770.23394219 7172116.41968508,1116768.15226771 7172128.54354244)'::geometry, 30));

Returns Linestring Empty. I'll submit that as a separate ticket

Answer 2

It is a 2.1.1 and above bug, because on "POSTGIS="2.0.1 r9979" GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.8.0, 6 March 2012" LIBXML="2.7.6"", the query works. Also on POSTGIS="2.1.0SVN" GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.7.1, 23 September 2009" GDAL="GDAL 1.7.3, released 2010/11/10" LIBXML="2.7.8" LIBJSON="UNKNOWN" (core procs from "2.1.0SVN" need upgrade) TOPOLOGY (topology procs from "2.1.0SVN" need upgrade) RASTER (raster procs from "2.1.0SVN" need upgrade) works.

I have upgraded to 2.1.2 and I still have the error.

Here is a link with a small portion from the dataset (.shp and sql dump), and here is the query having the problem:

    -- create the table for streets
    CREATE TABLE streets (
    gid integer NOT NULL,
    name varchar,
    geom geometry(Geometry, 3857)
    );
   -- insert the data as a shapefile or as a sql dump
   -- create the offset streets
   -- create column for right offset line
   ALTER TABLE streets ADD COLUMN rstreets geometry(Geometry, 3857);
   UPDATE streets SET rstreets = ST_OffsetCurve(geom, 30);
   -- create column for left offset line
   ALTER TABLE streets_merc ADD COLUMN lstreets geometry(Geometry, 3857);
   UPDATE streets  SET lstreets = ST_OffsetCurve(geom, -30);
   -- create the points table
   CREATE TABLE points (
       gid bigserial NOT NULL,
       name varchar,
   lineid integer,
   segmentid integer,
   geom geometry(Geometry, 3857)
    );
   -- populate the points table with the working query
   INSERT INTO points(name, lineid, segmentid, the_geom)
   SELECT name, gid, (ST_DumpPoints(ST_Segmentize(geom, 20))).path[1] AS segmentid, (ST_DumpPoints(ST_Segmentize(geom, 20))).geom AS the_geom
    FROM streets;
   -- populate the points table with the problematic query
   -- create the right points column
   ALTER TABLE points ADD COLUMN rpoints geometry(Geometry, 3857);
   INSERT INTO points(rpoints)
   SELECT (ST_DumpPoints(ST_Segmentize(rstreets, 20))).geom AS rpoints
   FROM streets;
   -- create the left points column
   ALTER TABLE points ADD COLUMN lpoints geometry(Geometry, 3857);
   INSERT INTO points(lpoints)
   SELECT (ST_DumpPoints(ST_Segmentize(lstreets, 20))).geom AS lrpoints
   FROM streets;