[postgis-users] Problems with ST_OffsetCurve

[Rémi Cura]

Oups I put a -15 translation in above example, it also works for -16 of
course like required.

Cheers,
Rémi-C


2014-02-03 Rémi Cura <remi.cura at gmail.com>:

> Hey,
> you use far too big coordinates.
> Please consider using st translate on your data, then curve offset, then
> inverse translate.
> This is mandatory (when using so many digits, you artificially increase
> the need for precision in numeric computing, which is problematic).
>
> It is true for all computation, also for "cleanness", you should use a
> custom srid defined as a translated version of your orgininal srid, and not
> manually put the translate number like I did in the following. It is best
> practice and easier to read/correct/maintain/ reuse.
>
> SELECT ST_AsText(ST_Translate(ST_Offsetcurve(ST_Translate(geom,-346000,
> -6861000),-15), +346000,+6861000)) FROM
> ST_AsText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
> ) AS geom
>
> Conceptually, it is more difficult for a computer to do 684738+1 than 12+1
> .
>
> Also , it should be noted that sometime curveoffset can't give a correct
> answer because there isn't a well defined one (like almost boucling lines).
>
> Cheers,
>
> Rémi-C
>
>
> 2014-02-03 Sandro Santilli <strk at keybit.net>:
>
> On Mon, Feb 03, 2014 at 11:43:37AM +0300, jakob ventin wrote:
>> > Hello all,
>> > I am using ST_OffsetCurve function to calculate offsets for lines and
>> polygons. I have a quit large amount of data, several tens of thousands of
>> features which I have to do these calculations for in an automated
>> processs. Now I have run into a problem: St_OffsetCurve crashes for some
>> geometries, e.g this geometry and value -16 for ST_OffsetCurve:
>> >  SELECT ST_OffsetCurve(geometry_line,-16) FROM table WHERE id =
>> 111;ERROR:  GEOSOffsetCurve: TopologyException: assigned depths do not
>> match at 346051.04711531324 6861597.9481203193
>>
>> Sounds like a robustness problem. It would be interesting to
>> see if using a fixed PrecisionModel solved the issue.
>> You can file a ticket for GEOS, an XML test for GEOS would
>> be able to test with both floating and fixed PrecisionModel.
>>
>> If fixed precisionmodel solves it this would be yet another
>> reason to expose support for that into PostGIS...
>>
>> --strk;
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at lists.osgeo.org
>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
>>
>
>
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