[Proj] Datum shifts in PROJ's EPSG table (The Netherlands and Belgium)

[Greg Troxel]

  > fromProj = pj_init_plus(+proj=latlong +ellps=bessel)
  > 
  > toProj   = pj_init_plus(
  > 		"+proj=sterea +lat_0=52.15616055555555 
  > 		"+lon_0=5.38763888888889 
  > 		"+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
  > 		"+towgs84=565.2369,50.0087,465.658,-0.406857330322398,0.350732676542563,-1.87
  > 		+units=m +no_defs)
  > 
  > pj_transform(fromProj, toProj, 1, 0, &lng, &lat, &alt)

This really seems wrong, since your input is actually WGS84, and thus
is not using the bessel ellipsoid.

I think you want proj to do several things in order

  convert from WGS84 geodetic (on the standard WGS84/GRS80 ellipsoid) to
  ECEF

  apply a datum shift from WGS84 to your local datum

  convert to geodetic in the bessel ellipsoid

  transform to the RD projection


You might try setting up this chain explicitly and cross-checking with
published coordinates of control points in the various
representations and datums.

-- 

    Greg Troxel <gdt at ir.bbn.com>