Projection definitions for epsg:2391-2393 (Finnish KKJ)

[Frank Warmerdam]

Rahkonen Jukka wrote:
> Hello,
> 
> For some reasons there are two versions of Finnish KKJ parameters hanging
> around in the projection libraries.  I checked that the situation is the
> same at least in MS4W and FW Tools Windows packages.  In the files
> "\FWTools1.2.2\proj_lib\epsg" and "\ms4w\proj\nad\epsg" the definition are
> like this: <2393> +proj=tmerc +lat_0=0 +lon_0=27 +k=1.000000 +x_0=3500000
> +y_0=0 +ellps=intl +units=m +no_defs  <>
...
> I think that the definitions in epsg file should be corrected. Or is there
> some reason, historical or other, for not including the towgs84 parameters
> there?

Jukka,

The epsg file is generated from the EPSG database and only includes towgs84
parameters for geographic coordinate systems that have one, and only one,
transformation from that GCS to WGS84 using 3 or 7 parameter transformations.

If there are multiple ways (multiple sets of parameters) then to be "safe"
none of them are used.

I don't know if that is the case in for KKJ or not without quite a bit of
digging.

If there was one clearly preferred set of parameters that you and everyone
else can agree on, then I can set an override in the epsg file generation
process to use that.  But I don't like to be in the position where I add
them at one persons suggestion, and then someone else emails me suggesting
different values.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org