Package: wnpp
Severity: wishlist
Owner: Bas Couwenberg <>

* Package name    : proj-rdnap
  Version         : 2008
  Upstream Author : RDNAP
* URL             :
* License         : RDNAPTRANS2008-NTv2
  Programming Lang: N/A
  Description     : RDNAP grid correction files for PROJ.4

Kadaster and Rijkswaterstaat CIV, working together under the name RDNAP,
developed RDNAPTRANS™2008, the precise and official transformation
between ETRS89 and the dutch national horizontal and vertical coordinate
reference systems the Stelsel van de Rijksdriehoeksmeting (RD) and the
Normaal Amsterdams Peil (NAP). A ‘simplified’ procedure has been
devolped which uses a NTv2-grid for the transformation between ETRS89
and RD as well as a VDatum-grid for the transformation between ETRS89
and NAP. This ‘simplified’ procedure has the following limitations:

 1) The rdtrans2008 NTv2-grid can only give identical results to
    RDNAPTRANS™2008 within 1 millimeter at ground level onshore and at
    mean seal level offshore. The horizontal deviation is approximately
    1 millimeter per 50 meter height difference from ground level or mean
    sea level.
 2) An exception to 1) is the border of the RDNAPTRANS™2008 correction
    grid. Transformation results within cells of the rdtrans2008 NTv2-grid
    that are intersected by the border of the RDNAPTRANS™2008 correction
    grid can result in deviations of up to 20 centimeter.
 3) The naptrans2008 VDatum-grid cannot be used to determine deflections
    of the vertical. For this the NLGEO2004 geoid model has to be used.
 4) The naptrans2008 VDatum-grid is referenced to the Bessel-1841 ellipsoid
    and cannot be used stand-alone, it has to be used in combination with
    the rdtrans2008 NTv2-grid.

Taking into account the limitations listed above, the rdtrans2008 NTv2-grid
and naptrans2008 VDatum-grid can be used as an alternative to
RDNAPTRANS™2008 to transform geographic ETRS89-coordinates to
projected RD-coordinates with grid correction applied and NAP-heights.
The figure in appendix 1 shows the precise and official RDNAPTRANS™2008
flow-chart on the left and on the right the flow-chart for the ‘simplified’

Note that, although the resulting RD/NAP and ETRS89 coordinates from the
transformation will be correct, geographic Bessel-1841 coordinates will
differ in both procedures and should only be considered as an intermediate

The package will be maintained within the Debian GIS team.

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