[gdal-dev] Re: org2ogr, KML, and srs definition

[Etienne Tourigny]

Brent,

to use that experimental feature (available in 1.9.0), you need to set
GDAL_FIX_ESRI_WKT=TOWGS84

Try the following:
GDAL_FIX_ESRI_WKT=TOWGS84 gdalsrsinfo <yourfile.shp>

If you see the towgs84 parameters in the PROJ.4 string, then it will
work with ogr2ogr.

This is documented in
http://www.gdal.org/ogr/classOGRSpatialReference.html#ad556dfdc04d9ec5f1714fc6b5e0eb6a6
More information here http://trac.osgeo.org/gdal/ticket/4345

If it works, please report here, and if not, please send me your
shapefile so I can make improvements

Etienne


On Sat, Feb 18, 2012 at 4:53 PM, Hermann Peifer <peifer at gmx.eu> wrote:
> On 18/02/2012 20:11, Brent Fraser wrote:
>>
>> I have some shapefiles I thought I would look at in Google Earth, so I
>> used ogr2ogr (v1.8.1) to convert them to KML:
>>
>> ogr2ogr -f "KML" Lines_OGR.kml Lines.shp
>>
>> but they appeared about 100 meters Northeast of my expectation, leading
>> me to believe there was a Datum problem.
>>
>
> OGR interprets your .prj file like this:
> +proj=utm +zone=35 +ellps=intl +units=m +no_defs
>
> ...and the EPSG code like this:
> +proj=utm +zone=35 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m
> +no_defs
>
> As there is no +towgs84 parameter in the 1st case, you end up with the 100m
> shift. In trunk, there is some code that should enable some sort of EPSG
> code auto-detection, but this is still experimental...
>
> Hermann
>
>
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