[OSRS-PROJ] conversion wgs-72 to lambert ntf

[Frank Warmerdam]

Christophe Couvreur wrote:
> Hello,
> 
> I begin with proj program.
> I would like know if with proj release 4, I can convert geodetic values
> (longitude, latitude) with ellipsoid WGS-72 to values in Lambert
> projection NTF.

Christophe,

Yes it can, but I think you will need to provide datum shift parameters for
WGS72 to WGS84 to get it too work.   You will also need to know that
particulars of the projection you want to convert to.

A quick scan of the EPSG database shows the following well known projected
coordinate systems based on the NTF datum (all with a Paris prime meridian ...
another issue):

27561,"NTF (Paris) / Lambert Nord France",9001,4807,18091,9801,8801,55.0,9105,88
02,0.0,9105,8805,0.999877341,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27562,"NTF (Paris) / Lambert Centre France",9001,4807,18092,9801,8801,52.0,9105,
8802,0.0,9105,8805,0.99987742,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27563,"NTF (Paris) / Lambert Sud France",9001,4807,18093,9801,8801,49.0,9105,880
2,0.0,9105,8805,0.999877499,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27564,"NTF (Paris) / Lambert Corse",9001,4807,18094,9801,8801,46.85,9105,8802,0.
0,9105,8805,0.99994471,9201,8806,234.358,9001,8807,185861.369,9001,,,,,,
27571,"NTF (Paris) / Lambert zone I",9001,4807,18081,9801,8801,55.0,9105,8802,0.
0,9105,8805,0.999877341,9201,8806,600000.0,9001,8807,1200000.0,9001,,,,,,
27572,"NTF (Paris) / Lambert zone II",9001,4807,18082,9801,8801,52.0,9105,8802,0
.0,9105,8805,0.99987742,9201,8806,600000.0,9001,8807,2200000.0,9001,,,,,,
27573,"NTF (Paris) / Lambert zone III",9001,4807,18083,9801,8801,49.0,9105,8802,
0.0,9105,8805,0.999877499,9201,8806,600000.0,9001,8807,3200000.0,9001,,,,,,
27574,"NTF (Paris) / Lambert zone IV",9001,4807,18084,9801,8801,46.85,9105,8802,
0.0,9105,8805,0.99994471,9201,8806,234.358,9001,8807,4185861.369,9001,,,,,,
27581,"NTF (Paris) / France I",9001,4807,18081,9801,8801,55.0,9105,8802,0.0,9105
,8805,0.999877341,9201,8806,600000.0,9001,8807,1200000.0,9001,,,,,,
27582,"NTF (Paris) / France II",9001,4807,18082,9801,8801,52.0,9105,8802,0.0,910
5,8805,0.99987742,9201,8806,600000.0,9001,8807,2200000.0,9001,,,,,,
27583,"NTF (Paris) / France III",9001,4807,18083,9801,8801,49.0,9105,8802,0.0,91
05,8805,0.999877499,9201,8806,600000.0,9001,8807,3200000.0,9001,,,,,,
27584,"NTF (Paris) / France IV",9001,4807,18084,9801,8801,46.85,9105,8802,0.0,91
05,8805,0.99994471,9201,8806,234.358,9001,8807,4185861.369,9001,,,,,,
27591,"NTF (Paris) / Nord France",9001,4807,18091,9801,8801,55.0,9105,8802,0.0,9
105,8805,0.999877341,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27592,"NTF (Paris) / Centre France",9001,4807,18092,9801,8801,52.0,9105,8802,0.0
,9105,8805,0.99987742,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27593,"NTF (Paris) / Sud France",9001,4807,18093,9801,8801,49.0,9105,8802,0.0,91
05,8805,0.999877499,9201,8806,600000.0,9001,8807,200000.0,9001,,,,,,
27594,"NTF (Paris) / Corse",9001,4807,18094,9801,8801,46.85,9105,8802,0.0,9105,8
805,0.99994471,9201,8806,234.358,9001,8807,185861.369,9001,,,,,,

A trivial transformation between WGS72 latlong and EPSG 27561 (Lambert Nord
France) might look like this:

cs2cs +proj=latlong +ellps=WGS72 +towgs84=0,0,0 +to +init=epsg:27561

This assumes that WGS72 coordinates are expressed relative to greenwich, and
that no datum shift (other than the ellipsoid conversion) is required between
WGS72 and WGS84.  A poor assumption if you are trying to be particularly
accurate.

If you look in the proj/nad/epsg file you will see that Lambert Nord
France uses the definition:

# NTF (Paris) / Lambert Nord France
<27561> +proj=lcc +lat_1=49.50000000000001 +lat_0=49.50000000000001 
+lon_0=2.33722917 +k_0=0.999877341 +x_0=600000 +y_0=200000 +a=6378249.2 
+b=6356515 +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs  no_defs <>

I hope this gets you started.

Best regards,

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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