[Proj] ED50 from C API
roger at opq.se
Wed Mar 28 09:04:19 EST 2007
I would like to convert WGS84 lat/longs from a GPS receiver into
northings and eastings in ED50, fixed in UTM zone 30N. I have tried the
following, but the results are always 100-150 meters off from what I
expect. What have I missed? I based this in the ESRI file in proj 4.4.9
Initialization (error checking removed here for clarity):
// From GPS WGS84
fromProj = pj_init_plus( "+proj=latlong "
// To ED50
toProj = pj_init_plus( "+proj=utm "
The call for each location:
lng = LONG * DEGREE_TO_RADIAN;
lat = LAT * DEGREE_TO_RADIAN;
alt = 0; // We do not give this a height
pj_transform(fromProj, toProj, 1, 0, &lng, &lat, &alt);
Input WGS84: lat=37.57508059 lng=-0.93032997 alt=0.00000000
Obtains: Easting=682771.459 Northing=4160841.260
But I am expecting: Easting=682876.090 Northing=4160892.020
There is a difference in location of 116.293 meters.
The error is in the initialization step. I suspect it is something that
is not in the ESRI file that I need to add when doing this from the C
API. But what?
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