[gdal-dev] EPSG:2065 / South-oriented Krovak support (Czech friends thoughts wanted !)

[Daniel Fenton]

Even,

I'm not sure if this helps, but in dealing with an issue with WKID 5514,
this WKT workers to properly convert data from WGS84. This was confirmed
against a customer's source data.
'
PROJCS["S-JTSK_Krovak_East_North",GEOGCS["GCS_S_JTSK",DATUM["Jednotne_Trigonometricke_Site_Katastralni",SPHEROID["Bessel_1841",6377397.155,299.1528128]],TOWGS84[589,76,480,0,0,0,0],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Krovak"],PARAMETER["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER["Pseudo_Standard_Parallel_1",78.5],PARAMETER["Scale_Factor",0.9999],PARAMETER["Azimuth",30.28813975277778],PARAMETER["Longitude_Of_Center",24.83333333333333],PARAMETER["Latitude_Of_Center",49.5],PARAMETER["X_Scale",-1],PARAMETER["Y_Scale",1],PARAMETER["XY_Plane_Rotation",90],UNIT["Meter",1],AUTHORITY["EPSG","102067"]]
'

Daniel

*Daniel Fenton*
*Software Engineer | Esri R&D*
*https://koopjs.github.io <https://koopjs.github.io>*
On Thu, Jan 28, 2016 at 12:05 PM Even Rouault <even.rouault at spatialys.com>
wrote:

> Hi,
>
> I'm having a look at the following all related issues :
> https://trac.osgeo.org/postgis/ticket/1940
> https://trac.osgeo.org/proj/ticket/185
> https://trac.osgeo.org/gdal/ticket/4762
>
> related to EPSG:2065 support, ie "S-JTSK (Ferro) / Krovak". There's an
> issue
> about the datum shift used, but that's an easy one compared to a more
> serious
> one regarding axis order.
>
> The proj.4 krovak method expects the first value of a coordinate pair to
> be a
> easting, and the second value a northing. Whereas original Krovak
> (EPSG:2065)
> is supposed to be southing first, westing second.
>
> https://trac.osgeo.org/gdal/ticket/4762 suggests to add a "+to_meter=-1"
> parameter. Which means that the coordinates supplied are first westing,
> second
> southing (instead of "+to_meter=-1", a cleaner equivalent way is to use
> "+axis=wsu", meaning westing,southing,up )
> But EPSG would mandate southing,westing.
>
> But admitedly, for less exotic coordinate systems with official EPSG axis
> order
> latitude,longitude (EPSG:4326...) or northing,easting (some Finland
> projected
> CRS for example) we have never introduced in GDAL WKT or proj.4 strings the
> +axis option, and the application/user does the coordinate switch itself
> before passing that to GDAL/proj.
>
> So, does that sound OK that a user providing coordinates advertized to be
> in
> EPSG:2065 does that in westing, southing order ? Or was this something
> particular to this user ? (I'd note that the dataset mentionned in the
> ticket
> is a GML resulting from a WFS server, and we all know the axis ordering
> issues
> related to WFS)
>
> What a mess...
> (Using EPSG:5221 which is the easting, northing variant avoids those
> headaches)
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
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