[gdal-dev] Problem re-projecting shapefile by using ogr2ogr

[Stefano Iacovella]

2012/12/13 deb <otrov at hush.ai>:
> Hi,
>
> I want to re-project shapefile from current projection (whatever that is) to ESPG:4326.
> My example layer (misc.shp) is in EPSG:31227:
>
>     > ogrinfo -al -so misc.shp
>     INFO: Open of `misc.shp'
>           using driver `ESRI Shapefile' successful.
>
>     Layer name: misc
>     Geometry: Line String
>     Feature Count: 10
>     Extent: (21.267388, 42.015857) - (21.270225, 42.017470)
>     Layer SRS WKT:
>     PROJCS["MGI_Balkans_zone_7_deprecated",
>         GEOGCS["GCS_MGI",
>             DATUM["Militar_Geographische_Institute",
>                 SPHEROID["Bessel_1841",6377397.155,299.1528128]],
>             PRIMEM["Greenwich",0],
>             UNIT["Degree",0.017453292519943295]],
>         PROJECTION["Transverse_Mercator"],
>         PARAMETER["latitude_of_origin",0],
>         PARAMETER["central_meridian",21],
>         PARAMETER["scale_factor",0.9999],
>         PARAMETER["false_easting",7500000],
>         PARAMETER["false_northing",0],
>         UNIT["Meter",1]]
>     id: Integer (10.0)
>
>
> As suggested by couple of sources from Google search results, I used this:
>
>     > ogr2ogr -t_srs EPSG:4326 misc_re.shp misc.shp
>
>
> And then investigate metadata of newly creates vector:
>
>     > ogrinfo -al -so misc_re.shp
>     INFO: Open of `misc_re.shp'
>           using driver `ESRI Shapefile' successful.
>
>     Layer name: misc_re
>     Geometry: Line String
>     Feature Count: 10
>     Extent: (-34.004490, 0.000230) - (-34.004490, 0.000230)
>     Layer SRS WKT:
>     GEOGCS["GCS_WGS_1984",
>         DATUM["WGS_1984",
>             SPHEROID["WGS_84",6378137,298.257223563]],
>         PRIMEM["Greenwich",0],
>         UNIT["Degree",0.017453292519943295]]
>     id: Integer (10.0)
>
>
> There is no projection (PROJCS) in metadata and coordinates are different from source vector.
> I then tried various EPSG codes, and I get PROJCS metadata, but Extent values are totally different for each projection, so even if I assume some units issue, there can't be that different units in existence.
>
There is no PROJCS as your target SRS is a geographic one. Indeeed you
can see the GEOGCS label.
 EPSG:31227 is not only deprecated, it was removed from EPSG database,
looking at epsg-registry.org I can't find it.
Anyway as the WKT states is a Transverse Mercator flavour the extent
sounds quite strange to me.

May be it is EPSG:3909?

For a gentle introduction to SRS, maps and projections you may have a look at

http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html

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