[Proj] +towgs84 approximation error

Jochem jochem.lesparre at kadaster.nl
Wed Mar 22 20:34:32 EST 2017

Hi Stefanos,

I have coordinates in an old national grid and a new national grid. Both
grids have TM projections on the international Hayfort ellipsoid. Both grids
have 7 parameter transformations to WGS84 defined by the government but not
published in EPSG. I want to do:

cs2cs +init=mygrids:old +to +init=mygrids:new -f %.4f <old_coords.txt

What I need is exactly what I explained in my first email: a 7 parameter
transformation without approximation error of 4 cm (this error is a bias,
not a standard deviation) in the formulas.

Regards, Jochem

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