[Proj] Lambert Conformal Conic

Irwin Scollar al001 at uni-koeln.de
Sun Apr 26 04:14:03 EST 2009

In France, the Institut Géographique National 
(IGN) has abandoned mapping using four Lambert 
secant conic zones which were in use after World 
War One based on the NTF (Nouvelle Triangulation 
de la France) of the late 19th and early 20th 
century and the Clarke 1880 ellipsoid.

Today, three variants are supported by IGN, one 
using a WGS84 ellipsoid covering the whole of the 
country called Lambert 93, one using the Clarke 
1880 ellipsoid like the old NTF based grid did, 
with the dual latitudes of the old NTF zone II 
and a different false Northing called Lambert 
Extended II, and one for higher precision using 9 
zones and the GRS80/WGS84 ellipsoid called 
Lambert CC (Coniques Conformes).  Lambert 93 is 
now the standard for most products from the IGN.

These recent developments are not included in 
Cliff Mugnier's ASPRS article of 2001:


For calculating single points in the new systems, 
IGN offers their interactive program Circé which 
has a user interface similar to Geotrans 2 from 
NGA with the supporting maths described in:



Lambert 93 and Lambert Extended II coordinates as 
well as GRS80 Lat/Lons can be viewed 
interactively  for high resolution aerial 
photographs with a number of overlays including 
the cadastral maps in metropolitan France at:


The formulae in the IGN  paper "transformaton.pdf 
" (note the missing i) appear to differ slightly 
from those for this projection in Snyder, US 
Geological Survey Professional Paper 1395, 4th 
Ed. 1987, pp. 107-109 as well as those in Cliff 
Mugnier's contribution to the 5th edition of the 
ASPRS Manual of Photogrammetry, p. 194-197 and in proj4 pj_lcc.c

A discussion similar to the recent one concerning 
the Transverse Mercator about the accuracy and 
speed of the different approaches for computing 
conformal grid values with the Lambert Conic 
secant projection for France and elsewhere would be greatly appreciated.

Irwin Scollar  

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