[gdal-dev] Reprojection shapefile using ogr2ogr from EPSG:28992 to EPSG:4326

[Pierric de Laborie]

In my case shapefile are uploaded to the server by users through a web page
(polygons represent the boundaries of a new protected natural site). So the
only information about the projection that I get is located in the .prj
file. I am not sure if there is a way to get the EPSG code automatically in
this case (?)

How can QGIS pick up the name of the EPSG code right (actually I knew that
the projection code was EPSG:28992 by opening the shapefile in QGIS and
checking the properties of the layer)   ?

In the case there is no way to get the EPSG code automatically: do you know
if ogr2ogr could send a warning/error that I would send back to the user
asking him to reproject the shapefile in WGS84 himself before uploading the
file?

Thanks in advance for your insights


2015-01-22 19:54 GMT+01:00 Even Rouault <even.rouault at spatialys.com>:

> Le jeudi 22 janvier 2015 19:43:50, Pierric de Laborie a écrit :
> > Hello,
> >
> > I do not understand why there seems to be a drift (about 100 meters) of
> the
> > polygons contained in a shapefile after reprojecting it to 4326 using the
> > following command :
> >
> > ogr2ogr -f 'ESRI Shapefile' -wrapdateline -t_srs EPSG:4326
> > destinationfile.shp sourcefile.shp
> >
> > The original prj file is the following. It is supposed to describe the
> > projection EPSG:28992  ( http://spatialreference.org/ref/epsg/28992/  )
> >
> > PROJCS["RD_New",GEOGCS["GCS_Amersfoort",DATUM["D_Amersfoort",
> > SPHEROID["Bessel_1841",6377397.155,299.1528128]],
> > PRIMEM["Greenwich",0.0],
> > UNIT["Degree",0.0174532925199433]],
> > PROJECTION["Double_Stereographic"],
> > PARAMETER["False_Easting",155000.0],
> > PARAMETER["False_Northing",463000.0],
> > PARAMETER["Central_Meridian",5.38763888888889],
> > PARAMETER["Scale_Factor",0.9999079],
> > PARAMETER["Latitude_Of_Origin",52.15616055555555],
> > UNIT["Meter",1.0]]
>
>
> This definition is outdated and has not the needed datum shift :
>
> $ gdalsrsinfo EPSG:28992
>
> PROJ.4 : '+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
> +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
> +towgs84=565.417,50.3319,465.552,-0.398957,0.343988,-1.8774,4.0725 +units=m
> +no_defs '
>
> OGC WKT :
> PROJCS["Amersfoort / RD New",
>     GEOGCS["Amersfoort",
>         DATUM["Amersfoort",
>             SPHEROID["Bessel 1841",6377397.155,299.1528128,
>                 AUTHORITY["EPSG","7004"]],
>
> TOWGS84[565.417,50.3319,465.552,-0.398957,0.343988,-1.8774,4.0725],
>             AUTHORITY["EPSG","6289"]],
>         PRIMEM["Greenwich",0,
>             AUTHORITY["EPSG","8901"]],
>         UNIT["degree",0.0174532925199433,
>             AUTHORITY["EPSG","9122"]],
>         AUTHORITY["EPSG","4289"]],
>     PROJECTION["Oblique_Stereographic"],
>     PARAMETER["latitude_of_origin",52.15616055555555],
>     PARAMETER["central_meridian",5.38763888888889],
>     PARAMETER["scale_factor",0.9999079],
>     PARAMETER["false_easting",155000],
>     PARAMETER["false_northing",463000],
>     UNIT["metre",1,
>         AUTHORITY["EPSG","9001"]],
>     AXIS["X",EAST],
>     AXIS["Y",NORTH],
>     AUTHORITY["EPSG","28992"]]
>
>
> >
> > Apparently QGIS could understand the projection file correctly and
> > reproject it to WGS84 with no problem. But it seems that for some
> specific
> > projections, GDAL does not reproject as expected.
>
> Shapefile .prj files don't include TOWGS84, so that's the likely
> explanation.
> Try adding -s_srs  EPSG:28992 to your ogr2ogr command line
>
> >
> >  Is it possible to force it by adding the projection specifications in
> one
> > of the files included in the following folder (linux debian install) :
> >  /usr/share/gdal   and how ?
> >
> > For example, I could see a file named gdal_datum.csv  containing the
> datum
> > "D_Amersfoort" specified in the prj file. However I could not find in any
> > other files the projection GCS_Amersfoort or RD_New as specified in the
> prj
> > file.
> >
> > Thanks for your help
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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