[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:
http://www.asprs.org/resources/grids/01-2001-france.pdf
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:
<http://professionnels.ign.fr/DISPLAY/000/526/700/5267002/transformaton.pdf>http://professionnels.ign.fr/DISPLAY/000/526/700/5267002/transformaton.pdf
(2004)
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:
<http://www.geoportail.fr/visu2D.do?ter=metropole>http://www.geoportail.fr/visu2D.do?ter=metropolehttp://www.geoportail.fr/visu2D.do?ter=metropole
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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