# [OSRS-PROJ] Older Stateplane Definitions

Paul Ramsey pramsey at refractions.net
Sun Jul 28 15:36:19 EDT 2002

```Interesting. Learn something new every day. For the benefit of all, here
is the ESRI WTK definition of NTF_Paris_France_I <27581>

PROJCS[
"NTF_Paris_France_I",
GEOGCS["GCS_NTF_Paris",
DATUM["D_NTF",
SPHEROID["Clarke_1880_IGN",6378249.2,293.46602]
],
PRIMEM["Paris",2.337229166666667],
],
PROJECTION["Lambert_Conformal_Conic"],
PARAMETER["False_Easting",600000],
PARAMETER["False_Northing",1200000],
PARAMETER["Central_Meridian",0],
PARAMETER["Standard_Parallel_1",55],
PARAMETER["Scale_Factor",0.999877341],
PARAMETER["Latitude_Of_Origin",55],
UNIT["Meter",1]
]

Here is the definition I got from OGR converting from WKT to Proj4:

+proj=lcc
+lat_1=55.000000000
+lat_2=0.000000000
+lat_0=55.000000000
+lon_0=0.000000000
+x_0=600000.000
+y_0=1200000.000
+a=6378249.200
+b=6356515.000
+units=m

As noted, there is no flag that the angular units are gradians-paris, so
they'll be misinterpretted as degrees-greenwich.
What is the nicest way to properly represent the gradian projections in
proj4 syntax? A quick hack would be to directly convert the angular
units in the projection definition from gradians-paris to
degrees-greenwich. That would still leave open the problem of how to

P.

Craig Bruce wrote:
>
> The definitions of the following coordinate systems are incorrect:
>
> # Nord_de_Guerre <27500>
> # NTF_Paris_France_I <27581>
> # NTF_Paris_France_II <27582>
> # NTF_Paris_France_III <27583>
> # NTF_Paris_France_IV <27584>
> # NTF_Paris_Nord_France <27591>
> # NTF_Paris_Centre_France <27592>
> # NTF_Paris_Sud_France <27593>
> # NTF_Paris_Corse <27594>
>
> As indicated previously, they are incorrect because the angluar parameters
> are actually in Gradians relative to the Paris Prime Meridian but PROJ will
> assume that they are in Degrees relative to the Greenwich Prime Meridian.
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