On 8/16/08, Koen Mannaerts [fietsnet.be] <[EMAIL PROTECTED]> wrote: > > Hi all, > > I noticed that ogr2ogr in FWtools 1.0.0.a7 returns a different result than > ogr2ogr in FWtools 2.2.0, 2.2.1.
Koen, The behavior of PROJ.4 changed between PROJ 4.5.x and PROJ 4.6.0. In particular, PROJ.4 will no longer attempt to apply a change of ellipsoid when going between different ellipsoids if no datum information is provided. > No doubt it's due to what I pass as arguments. The idea is to convert > Belgian Lambert, Belgian Datum shapefiles to Lat/Lon WGS84. > With the following arguments 1.0.0.a7 does this correctly, 2.2.1 produces > polylines ~110m off to the north west (Belgium). > > -f "ESRI Shapefile" -s_srs "+proj=lcc +lat_2=49.8333339 +lat_1=51.166667 > +lat_0=90.0000000 +lon_0=4.3674867 +x_0=150000.013 +y_0=5400088.438 +units=m > +ellps=intl > +towgs84=-99.059,53.322,-112.486,0.419,-0.830,1.885,-0.999999" > -t_srs "+proj=latlong +ellps=WGS84" I would suggest using +datum=WGS84 in the second definition, instead of (or addition to) +ellps=WGS84. You will also need some datum shift info for the intl ellipsoid. If you want the old behavior, provide +towgs84=0,0,0. This means only a change of ellipsoid will be applied, but no other datum shifting will be done. > Do I need to express the argument otherwise to make it work in newer > versions? Please also keep in mind that if you play "fast and loose" with datum shifts, there is a substantial risk that the results are not accurate. At the best of times, a datum shift usually involves some error due to the approximate nature of datum shift formulas. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev