[Qgis-developer] Belge 1972 / Belgian Lambert 72 (31370) - towgs84 parameters

[Thibaut Gheysen]

Hi,

I have a problem in QGIS 1.4.0 when I reproject a gpx file into Belgian
lambert 72 coordinate system : the waypoints are not correctly placed on the
map (see the image
http://www.fsagx.ac.be/gf/outilslogiciels/Garbel/proj4.jpg, correct
positions are in red). In QGIS, the towgs84 parameters are
'+towgs84=106.869,-52.2978,103.724,-0.33657,0.456955,-1.84218,1' for this
coordinate system. According to a discussion on the proj.4 mailing list (
http://lists.maptools.org/pipermail/proj/2010-January/005016.html), the
correct parameters seems to be
'+towgs84=-99.059,53.322,-112.486,0.419,-0.830,1.885,-1' (accurate to a
meter) or
'+towgs84=-106.8686,52.2978,-103.7329,-0.3366,0.457,-1.8422,-1.2747'
(accurate to 20 cm).

Best regards,
Thibaut.
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