Re: [gdal-dev] adding points to geometries
I would have thought : create a linesegment that is the equator and perform an intersection between that linesegment and the target geometry to identify the point in question and then create a new geometry with the new point, or something like that. I am not sure what it would mean to add a point to polygon crosses the equator - I would guess that would mean adding a vertex at the equator, in which case I think the intersection would return a line (I have never done it) and the vertices in question would be the points of the returned linesegment. On Sun, 26 Jan 2025 at 10:26, Javier Jimenez Shaw via gdal-dev < gdal-dev@lists.osgeo.org> wrote: > Hi > > I have a vector layer (like /usr/share/qgis/resources/data/world_map.gpkg) > and I need to add a point at latitude 0 for every segment (in line or > polygon) that crosses the equator. > > How can I do it? > > Thanks, > Javier. > ___ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev > ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] adding points to geometries
Hi I have a vector layer (like /usr/share/qgis/resources/data/world_map.gpkg) and I need to add a point at latitude 0 for every segment (in line or polygon) that crosses the equator. How can I do it? Thanks, Javier. ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] adding points to geometries
Thanks Paul I don't know if I was clear. Every segment that crosses the equator should become two segments, with the common point at lat=0. (I do not need the points themselves, I just want to add points to the lines and polygons, making "explicit" where they cross the equator). On Sun, 26 Jan 2025 at 13:37, Paul Harwood wrote: > I would have thought : create a linesegment that is the equator and > perform an intersection between that linesegment and the target geometry to > identify the point in question and then create a new geometry with the new > point, or something like that. > > I am not sure what it would mean to add a point to polygon crosses the > equator - I would guess that would mean adding a vertex at the equator, in > which case I think the intersection would return a line (I have never done > it) and the vertices in question would be the points of the returned > linesegment. > > On Sun, 26 Jan 2025 at 10:26, Javier Jimenez Shaw via gdal-dev < > gdal-dev@lists.osgeo.org> wrote: > >> Hi >> >> I have a vector layer (like >> /usr/share/qgis/resources/data/world_map.gpkg) and I need to add a point at >> latitude 0 for every segment (in line or polygon) that crosses the equator. >> >> How can I do it? >> >> Thanks, >> Javier. >> ___ >> gdal-dev mailing list >> gdal-dev@lists.osgeo.org >> https://lists.osgeo.org/mailman/listinfo/gdal-dev >> > ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] adding points to geometries
Create a new geometry, iterate through each segment of the old geometry if the segment does not intersect the equator, add that segment to the new geometry, else, use the intersection point to create two segments in the new geometry. On Sun, 26 Jan 2025 at 12:49, Javier Jimenez Shaw wrote: > Thanks Paul > > I don't know if I was clear. Every segment that crosses the equator should > become two segments, with the common point at lat=0. > (I do not need the points themselves, I just want to add points to the > lines and polygons, making "explicit" where they cross the equator). > > On Sun, 26 Jan 2025 at 13:37, Paul Harwood wrote: > >> I would have thought : create a linesegment that is the equator and >> perform an intersection between that linesegment and the target geometry to >> identify the point in question and then create a new geometry with the new >> point, or something like that. >> >> I am not sure what it would mean to add a point to polygon crosses the >> equator - I would guess that would mean adding a vertex at the equator, in >> which case I think the intersection would return a line (I have never done >> it) and the vertices in question would be the points of the returned >> linesegment. >> >> On Sun, 26 Jan 2025 at 10:26, Javier Jimenez Shaw via gdal-dev < >> gdal-dev@lists.osgeo.org> wrote: >> >>> Hi >>> >>> I have a vector layer (like >>> /usr/share/qgis/resources/data/world_map.gpkg) and I need to add a point at >>> latitude 0 for every segment (in line or polygon) that crosses the equator. >>> >>> How can I do it? >>> >>> Thanks, >>> Javier. >>> ___ >>> gdal-dev mailing list >>> gdal-dev@lists.osgeo.org >>> https://lists.osgeo.org/mailman/listinfo/gdal-dev >>> >> ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] adding points to geometries
Hey Javier, Maybe create 2 geometries, southern and northern hemisphere, then do an intersection of both with your source geometries. You would have to create new fid as the new geom's would the same fid. Untested, something like this: ogr2ogr -dialect sqlite -sql @newGeom.sql target.gpkg source.gpkg newGeom.sql select r.fid ,r.geom from ( select fid ,st_intersection(MakeCircle(0, 90, 4326, .001), geom) as geom from mygeoms union all select fid ,st_intersection(MakeCircle(0, -90, 4326, .001), geom) as geom from mygeoms ) r Hope that helps, Scott On 1/26/25 02:14, Javier Jimenez Shaw via gdal-dev wrote: Hi I have a vector layer (like /usr/share/qgis/resources/data/ world_map.gpkg) and I need to add a point at latitude 0 for every segment (in line or polygon) that crosses the equator. How can I do it? Thanks, Javier. ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
