Shift to WGS84 on two coordinate systems.

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Shift to WGS84 on two coordinate systems.

Ari Jolma
Dear geotiff developers and users,

The finnish "KKJ" coordinate system has got officially endorsed (JHS
153) values for the towgs84 parameter. These have been added to the
Proj.4 epsg file (4123, 2391-4, 3386-7). I guess these parameters should
be added to the gcs file of libgeotiff too?

Also, Proj.4, since version 4.6.0, requires explicit towgs84 parameters
to do datum transformations. As ETRS89 (epsg 4258 and several others -
ETRS89 is a widely used new European reference system, it is endorsed by
European Commission since 1999) does not have them, it causes programs
like ogr2ogr, when used with EPSG codes, to not work as well as they should.

ETRS89 is for practical purposes the same as WGS84. This statement is
backed by NIMA TR8530.2 (http://earthinfo.
nga.mil/GandG/publications/tr8350.2/tr8350_2.html). Thus the towgs
parameters for ETRS89 should be 0's. I guess the method code in gcs.csv
should also be changed to 9603, 6 or 7 since the current 6422 leads to
ignoring the towgs84 parameters at least in GDAL.

See also:

http://trac.osgeo.org/proj/ticket/15
http://trac.osgeo.org/gdal/ticket/2639

Best regards,

Ari

--
Prof. Ari Jolma
Environmental Management Information Technology
Teknillinen Korkeakoulu / Helsinki University of Technology
tel: +358 9 4511 address: POBox 5300, 02015 TKK, Finland
Email: ari.jolma at tkk.fi URL: http://geoinformatics.tkk.fi


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