[Proj] WGS84 to ED50

[Roger Oberholtzer]

On Wed, 2007-12-26 at 14:39 +0100, Oscar van Vlijmen wrote:
> A bit late reply, but might be still of some use....
> 
> > From: Roger Oberholtzer
> > Date: Mon, 19 Nov 2007 15:50:17 +0100
> > Subject: [Proj] WGS84 to ED50
> > 
> > Is anyone using proj to convert WGS84 latitudes and longitudes into ED50
> > (Spain and Portugal) northings and eastings?
> > 
> > My attempts get me to within a couple of meters of values calculated by
> > Trimble and Applanix (which are within a mm of each other). I did ask a
> > question about this a while back and got some answers that improved my
> > values by some 100 meters. But I never did get the values I need. So I
> > am trying again.
> > 
> .....
> 
> > When I transform:
> > 
> > lat=42.87645687 lng=-4.88298199 alt=0.00000000
> > 
> > I get Easting=346318.770 Northing=4749022.461
> > 
> > but I need Easting=346319.686 Northing=4749023.634
> > 
> .....
> > 
> > As Applanix and Trimble provide the same values for Spain (the ones I am
> > trying to get from proj), they must be using an existing and agreed upon
> > method. I would be surprised if proj couldn't do the same, if I could
> > just figure out how to tell it to do so!
> > 
> > The Applanix provides this information on their calculations:
> > 
> > Mapping frame datum: ED50_ESPA?A ; a = 6378388.000000; 1/f =
> > 297.000000;
> > Coordinate transformation from WGS84 to mapping frame datum
> > dX = 125.098545; dY = 76.000054; dZ = 156.198703; f =
> > 0.999991695369;
> > R1 = 0.000000000000; R2 = 0.000000000000; R3 = -0.000005473550;
> > sequence of the rotations: x,y,z,1
> > Mapping frame projection : TM;
> > central meridian = -3.000000 deg;
> > latitude of the grid origin = 0.000000 deg; grid scale factor =
> > 0.999600:
> > false easting = 500000.000000 m; false northing = 0.000000 m;
> > 
> 
> With these parameters - in the proper units - I get for x,y:
> 346319.6988, 4749023.4599 m
> Differences with the 'needed' values:
> dx = 0.013; dy = 0.174 m
> I assumed an 'exact' first-order coordinate frame rotation model, order XYZ,
> then scale.
> I think the given rotation angles are in radians, so I converted them to arc
> seconds.
> Note that PROJ uses a position vector rotation model and a simple transform
> method.

Your answer is not too late. I have not sorted this issue. What exactly
did you change to obtain your results? Which angles were in radians
instead of arc seconds? Was there anything else?

You've hooked me...

> 
> 
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-- 
Roger Oberholtzer

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