[Proj] MapInfo coordsys to proj.4 syntax

[Anthony Dunk]

Hi Paul,

NTF uses a prime meridian of 2.337229166667 (Paris), not Greenwich.

Below is the correct PROJ string for converting from Lat/Lon WGS84 to
projected NTF (French Lambert II Centre).

cs2cs +proj=latlong +a=6378137.0 +rf=298.257223563 +towgs84=0,0,0 +to
+proj=lcc +lon_0=2.337229166667 +lat_0=46.8 +lat_1=45.898918964419
+lat_2=47.696014502038 +x_0=600000 +y_0=200000 +a=6378249.2
+rf=293.4660213 +towgs84=-168,-60,320,0,0,0,0 +units=m +no_defs 

Using this an input point of 2.33333E, 48.8667N is projected to
599766.90 mE, 429819.60 mN. This agrees with MapInfo's projection of
the same point.

Anthony.

--- Paul Surgeon <surgpub at telkomsa.net> wrote:

> I'm trying to convert a MapInfo coordinate system into something that
> proj.4 
> understands but my high school maths doesn't seem to be helping me
> much.
> 
> The TAB files look like this :
> Type "RASTER"
> (830000.00,2050000.00) (0,0) Label "Pt 1",
> (840000.00,2050000.00) (2000,0) Label "Pt 2",
> (840000.00,2040000.00) (2000,2000) Label "Pt 3",
> (830000.00,2040000.00) (0,2000) Label "Pt 4"
> CoordSys Earth Projection 
> 3,1002,7,0,46.8,45.898918964419,47.696014502038,600000,2200000
> Units "m"
> 
> I've read some MapInfo docs and managed to break it down to :
> Name of projection = CoordSys Earth Projection 3
> Projection type = 3 = Lambert Conformal Conic
> Datum = 1002 = NTF (Paris)
> Ellipsoid = Modified Clark 1880
> Units = 7 = meters
> Origin lon = 0 (central meridian)
> Origin lat = 46.8
> Standard parallel 1 = 45.898918964419
> Standard parallel 2 = 47.696014502038
> False Easting = 600000
> False Northing = 2200000
> 
> I tried to use one of the standard NTF (Paris) EPSG definitions as a
> base to 
> work from but that doesn't seem to work.
> 
> My attempt :
> +proj=lcc +lon_0=0.0 +lat_0=46.8 +lat_1=45.898918964419
> +lat_2=47.696014502038 
> +k_0=0.99987742 +x_0=600000 +y_0=2200000 +a=6378249.2 +b=6356515 
> +towgs84=-168,-60,320,0,0,0,0 +pm=greenwich +units=m +no_defs
> 
> I assigned this srs definition with gdal_translate and then used
> gdalwarp to 
> warp the raster into a standard UTM zone.
> However I must be really far out with the proj.4 syntax because when
> I try to 
> lay the resulting raster over another it's so far out that I can't
> identify 
> anything common between the two images.
> 
> Any ideas where I'm going wrong?
> Paul
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj
> 




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