[Proj] UTM ED50 to ETRS89 datum shift problem

[Oscar van Vlijmen]

> From: "karel cech"
> Date: Mon, 4 Dec 2006 13:20:37 +0100
> Subject: [Proj] UTM ED50 to ETRS89 datum shift problem
> 
> Hi list,
> I have a problem with changing datum with cs2cs using 7 parameter
> shift from ED50/UTM30 to ETRS89. The result differs a lot from
> transformation results made by Carthographic Institute of Valencia
> (they work with ESRI and ERMapper)
> My test point has following coordinates (ED50/UTM30, EPSG:23030)
> 720931.9
> 4376574.85
> What I would like to obtain is aproximatly this (ETRS89, EPSG:25830):
> 720821.51
> 4376365.31
> However, cs2cs gives me
> 720748.93
> 4376357.47
> 
> The 7 parameters are defined by spanish institutions.
> 
> The debug output from cs2cs (proj 4.4.9.):
> 
> cs2cs -v +proj=utm +zone=30 +ellps=intl
> +towgs84=-131.0320,-100.2510,-163.3540,1.2438,0.0195,1.1436,9.3900
> +units=m +to +proj=utm +ellps=GRS80 +zone=30 +units=m -r <<EOF

....

It is possible that your transformation parameters were for the coordinate
frame rotation model. If I negate the rotation angles to force them to
position vector rotations, I get with my stuff:
x=720821.512; y=4376365.309
which seems to be spot on.
So, try:
+towgs84=-131.0320,-100.2510,-163.3540,-1.2438,-0.0195,-1.1436,9.3900