Geometry Boost List: Re: [geometry] epsg : 3857

From: Ahmet Temiz (ahmettemiz88_at_[hidden])
Date: 2019-09-23 17:30:59

Thank you,
Adam,
I am going to drape the boost-geometry data over openstreetmap ultimately.
I am dealing with a web application and use open street map as base layer.
Consequently the geometric data has to comply with openstreetmap. Epsg3857
Is the projection of openstreetmap that requires.
Besides I store all my data in epsg3857.

Regards

23 Eyl 2019 Pzt, saat 16:56 tarihinde Adam Wulkiewicz via Geometry <
geometry_at_[hidden]> şunu yazdı:

> Hi,
>
> W dniu 23.09.2019 o 10:57, Mateusz Loskot via Geometry pisze:
> > On Mon, 23 Sep 2019 at 10:38, Ahmet Temiz via Geometry
> > <geometry_at_[hidden]> wrote:
> >> Hi,
> >> I am not sure how I can define epsg : 3857 in boost geometry
> > Should be something along these lines:
> >
> > #include <boost/geometry/srs/epsg.hpp>
> > #include <boost/geometry/srs/projection.hpp>
> >
> > boost::geometry::srs::projection<> prj =
> boost::geometry::srs::epsg(3857);
> > boost::geometry::point_xy<double,  epsg<2040>> my_point(0, 0);
> >
> > Also, search through the source code of the Boost.Geometry tests
> > for more details about how `epsg` and `projection` can be used.
>
> This is not correct. The point type can only take cs::cartesian,
> cs::spherical or cs::geographic. EPSG:3857 is web/spherical mercator
> projection so to represent the points you'll use bg::cs::cartesian. The
> problem with this is that the algorithms will treat the coordinates as
> purly cartesian so the globe won't wrap around behind the antimeridian.
>
> What would you like to do exactly?
> Do you want to convert to or from it to some other SRS or do you have
> cartesian coordinates in EPSG:3857 and want to use some Boost.Geometry
> algorithms?
>
> Adam
>
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> Geometry_at_[hidden]
> https://lists.boost.org/mailman/listinfo.cgi/geometry
>
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