[Proj] Ellipsoide

[Jan Hartmann]

Hi Peter,

De subject has been discussed recently on the PostGIS list, starting with

http://postgis.refractions.net/pipermail/postgis-users/2006-October/013565.html

Currently, PROJ does *NOT* by default take into account the datum shift 
between ellipsoides for Belgium (it will do so in a next release). To 
get the proper conversion, use the following parameter string:

+proj=lcc +lat_1=51.16666723333333 +lat_2=49.8333339 +lat_0=90
+lon_0=4.367486666666666 +x_0=150000.013 +y_0=5400088.438 +ellps=intl
+towgs84=106.868628,-52.297783,103.723893,0.336570,-0.456955,1.842183,1.0000012747
+units=m +no_defs

The towgs84 numbers are from: http://www.ngi.be/NL/NL4-4.shtm

Regards,

Jan Hartmann
Department of Geography
University of Amsterdam


Peter Bogaert wrote:
> Deal all,
> 
> I have a small question concerning the proj4 library.
> When i convert data from eg. a Belgian Lambert 72 coördinate system (ellipsoide
> International 1924) to a UTM coördinate system (ellipsoide WGS84), does cs2cs
> take into account the different ellipsoïdes? Does the proj4 take into account
> the different ellipsoides or not? Do i have to program a convertion for the
> lat/lon coordinate shift between different ellipsoides or not?
> 
> Kind Regards
> Peter Bogaert
> 
> Ghent University
> Belgium
> peter.bogaert at skynet.be
> 
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