[postgis-users] St_OffsetCurve - gaps in the line

[McDonaldR]

Hello

I managed to get it to work by adding ST_Simplify to the mix like this:
SELECT row_number() OVER () AS gid,
    gm_scrim_master_b.esu_id,
    st_curvetoline(st_offsetcurve(st_simplify(gm_scrim_master_b.geometry, 0.15), 3::double precision, 'quad_segs=8 join=round'::text)) AS geometry
   FROM roads.gm_scrim_master_b
  WHERE st_isvalid(gm_scrim_master_b.geometry);
I am going to be out of the office for a few days – back next week and will file a ticket if required.

Thanks

Ross

From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf Of Darafei "Kom?pa" Praliaskouski
Sent: 15 February 2018 11:48
To: PostGIS Users Discussion
Subject: Re: [postgis-users] St_OffsetCurve - gaps in the line

Hi Ross,

Can you please file a ticket on https://trac.osgeo.org/postgis/ and share the geometry that reproduces behavior there, in form of WKB?

ср, 14 февр. 2018 г. в 21:19, McDonaldR <McDonaldR at angus.gov.uk<mailto:McDonaldR at angus.gov.uk>>:
Hi List

I’m using the following query to offset my geometry from a road centre line.

SELECT row_number() OVER () AS gid,
    gm_scrim_master_b.esu_id,
    st_curvetoline(st_offsetcurve(gm_scrim_master_b.geometry, 3::double precision, 'quad_segs=8 join=round'::text)) AS geometry
   FROM roads.gm_scrim_master_b
  WHERE st_isvalid(gm_scrim_master_b.geometry);

SELECT row_number() OVER () AS gid,
    gm_scrim_master_b.esu_id,
    st_curvetoline(st_offsetcurve(gm_scrim_master_b.geometry, -3::double precision, 'quad_segs=8 join=round'::text)) AS geometry
   FROM roads.gm_scrim_master_b
  WHERE st_isvalid(gm_scrim_master_b.geometry);

If I offset one way I get a nice complete line.  If I go the other way I get a line with gaps in it.  The source data is LINESTRING and I am checking validity to see if that is an issue.  Anyone got any suggestions as to where to start looking?

Thanks in advance

Ross

[cid:image001.png at 01D3A5AF.0FD714D0]

Ross McDonald | GIS Data Coordinator | Angus Council, People, IT | Angus House, Orchardbank Business Park, Sylvie Way, Forfar DD8 1AT | t: 01307 476419


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