[gdal-dev] adding points to geometries

[Javier Jimenez Shaw]

Hey Scott

You gave me an idea: cut first with a region on the north hemisphere and
then the south.
The circle does not work as expected. In EPSG:4326 you need a rectangle.
First I created different entries, adding 10000 to the fid to avoid
collisions.
But later I decided to just "st_collect" the polygons in a single
multipolygon (per entry). The final sql is like this:

select
    fid, name, iso_a2, iso_a3
    ,coalesce(
        st_collect(
            st_intersection(
                ST_GeomFromText('MULTIPOLYGON(((-180 90, -180 0, 180 0, 180
90, -180 90)))'),
                geom),
            st_intersection(
                ST_GeomFromText('MULTIPOLYGON(((-180 -90, -180 0, 180 0,
180 -90, -180 -90)))'),
                geom)
        ),
        geom) as geom
from countries

Thank you.


On Sun, 26 Jan 2025 at 17:33, Scott via gdal-dev <gdal-dev at lists.osgeo.org>
wrote:

> 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 at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/gdal-dev
>
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