Thanks for the suggestions and feedback everyone.
On 26 November 2013 08:49, Rémi Cura <remi.c...@gmail.com> wrote: > About sharp turns : you could use a small buffer then errosion or straight > skeleton (out of the box with sfcgal). > > For the flat encapt I suggest you to use st_split afterward. > > Cheers, > > Rémi-C > > > 2013/11/26 Mike Toews <mwto...@gmail.com> >> >> On 26 November 2013 06:04, James David Smith >> <james.david.sm...@gmail.com> wrote: >> > 2) Now I buffer it: >> > >> > SELECT ST_Buffer( >> > ST_GeomFromText( >> > 'LINESTRING(555936.152 200920.582000002,555938.312000002 >> > 200908.102000002,555943.112000001 200883.142000001,555953.192000001 >> > 200839.702,555964.471999999 200798.181999998,555974.312 >> > 200764.342000002,555983.912 200744.182000002,555990.554 >> > 200733.721000003,555993.512 200729.062000005,555995.778000002 >> > 200726.756000001,556006.952000001 200715.382000001,556024.232 >> > 200698.822000002,556036.597999999 200687.931,556050.392000001 >> > 200675.782000002,556055.914 200671.265000002,556071.512 >> > 200658.502000002,556094.915000001 200640.537000002,556095.451000001 >> > 200640.152000001,556113.992000001 200628.742000001,556138.472000001 >> > 200616.502000004,556159.112000002 200605.942000002,556180.232000001 >> > 200589.862000002,556207.592 200568.022000002,556217.912000002 >> > 200558.182,556228.472000001 200545.702,556240.472 >> > 200527.702000003,556251.992000001 200509.221999999,556253.237000001 >> > 200506.732000003,556258.952 200495.302000001,556268.000000001 >> > 200478.000000002,556279.592 200458.582000002,556300 >> > 200431.000000002,556351.000000002 200364,556349.253 >> > 200366.234000001)'), 1000, 'endcap=flat join=round'); >> >> Hi James, >> >> I just had a spin with this geometry in JTS TestBuilder, in Buffer > >> BufferWithParams. This graphical tool has similar controls as >> ST_Buffer, but is slightly more interactive. I get pretty much the >> same result, with anomalies on both ends of the linestring. GEOS (used >> by PostGIS) is a C++ port of JTS, so this is no surprise to see the >> same results. Only buffers less than 200 look normal. >> >> The oddness at the bottom is explained by a small J-shaped kink at the >> end of the linestring, which has a short and very sharp angle (nearly >> 360 degrees or 0 degrees), which makes the last segment go upwards and >> nearly parallel to the second-to-last segment of the linestring. >> Removing the last coordinate fixes things on the lower part. This is >> most likely a digitization error. >> >> If you have heaps of these geometries that need cleaning up, you could >> write a function to return the maximum vertex angle in a linestring, >> and filter out the sharp ones, e.g. > 350 degrees or < 10 degrees, >> then check and fix these up manually. >> >> On the upper-right part of the buffer, the polygon is clearly buffered >> by the correct distance from the middle of the line, but the clip from >> the top cap carves it a bit funny. I've seen this before too, and I'm >> not sure if anything can be done about this part. >> >> -Mike >> _______________________________________________ >> postgis-users mailing list >> postgis-users@lists.osgeo.org >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > > > > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users