[Proj] Belge 1972 / Belgian Lambert 72 (31370) - towgs84parameters

Thibaut Gheysen gheysen.t at gmail.com
Fri Jan 22 03:37:05 EST 2010

Thanks Jan and Mikael for your responses.
As suggested, I have forwarded this bug to the QGIS developer mailing list.


2010/1/21 Jan Hartmann <j.l.h.hartmann at uva.nl>

> On 21-Jan-10 12:52, Mikael Rittri wrote:
> Jan Hartmann wrote:
> > No, if QGIS uses PROJ, this is just an error.
> Okay, you may be right that QGIS does not use the file gcs.override.csv.
> But I see that the nad/epsg file of PROJ.4 contains the same erroneous
> +towgs84 parameters for Belge 1972 as the gcs.override.csv.
> (At least PROJ version 4.6.1).
> I have been quoting from PROJ 4.7. The older towgs parameter is not exactly
> erroneous, it's just a bit les exact
> > PROJ and EPSG use opposite rotational formulas, and PROJ uses degrees,
> EPSG radians.
> I don't agree in the general case.  PROJ uses the Position Vector
> Transform, while EPSG is neutral on the rotation sign convention:
> they use the same sign convention as the original source.
> And PROJ uses arc seconds for rotations, while EPSG is neutral
> on the angle unit: they use the same angle unit as the original source
> (usually arc seconds, but sometimes microradians or radians).
>      For the EPSG transforms you quote, EPSG use arc-seconds
> for the rotations, but either the Position Vector Transform or the
> Coordinate Frame Rotation depending on whether they got the
> transform from Eurogeographics or directly from Belgium.
>  My information was for the Dutch and Belgian cases, as from the official
> documents. I don't know on what principles EPSG operates, I guess they just
> take it as they get it. It is not an easy-to-use database.
> Jan
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