Without closure it is not possible to say what orientation a linestring has.
ST_IsPolygonCW(ST_MakePolygon(ST_AddPoint(linestring, ST_StartPoint(linestring)))) P > On Feb 16, 2022, at 11:31 PM, Shaozhong SHI <shishaozh...@gmail.com> wrote: > > How about each line gets split into segments. . Each segment is constructed > with two points (current and next points. > Then, calculate bearing/azimuth > Then, determine whether it is clockwise or counter-clockwise. > > Can this be done? > > Regards, > > David > > On Wed, 16 Feb 2022 at 20:39, Marcin Mionskowski > <mionskowskimar...@gmail.com> wrote: > It doesn't make sense for lines. > Imagine LINESTRING(1 0,1 1) - which "part of a square" is this i.e. where is > "the center of the square": (1) 0.5,0.5 or (2) 1.5,0.5? > If (1) it's CCW, if (2) CW. > > > śr., 16 lut 2022 o 21:29 Shaozhong SHI <shishaozh...@gmail.com> napisał(a): > The problem now is that I can not find anything for lines. > > Anything like ST_IsPolygonCW|ST_IsPolygonCCW for lines for instance, > something like ST_IsLineCW|ST_IsLineCCW. > > Regards, > > David > > On Wed, 16 Feb 2022 at 19:43, Marcin Mionskowski > <mionskowskimar...@gmail.com> wrote: > Assuming simple polygons, composed from exterior ring only (i.e. no > multipolygons), I think that you are looking for a function > {ST_IsPolygonCW|ST_IsPolygonCCW}. > > Greetings, > Marcin > > śr., 16 lut 2022 o 19:55 Imre Samu <pella.s...@gmail.com> napisał(a): > > how vertices run? clockwise or anti-clockwise? > > maybe the: > https://postgis.net/docs/ST_Angle.html "Computes the clockwise angle between > two vectors." > or https://postgis.net/docs/ST_Azimuth.html > > regards, > Imre > > > Shaozhong SHI <shishaozh...@gmail.com> ezt írta (időpont: 2022. febr. 16., > Sze, 17:06): > Can we use PostGIS to find out how vertices run? clockwise or anti-clockwise? > > Regards, > > David > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/postgis-users