[Proj] +towgs84 approximation error

[Clifford J Mugnier]

How many coordinate pairs?  For that level of desired accuracy you're going to need more than 100 points.  Is that reasonable?

Sent from Cliff Mugnier's iPhone

> On Mar 22, 2017, at 8:34 PM, Jochem <jochem.lesparre at kadaster.nl> wrote:
> 
> 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
>> new_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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