[OSRS-PROJ] Projection parameters for Italian old IGM?

Gerald I. Evenden gerald.evenden at verizon.net
Tue Apr 29 14:21:33 EDT 2003

The variety of names for the Transverse Mercator projection creates
a hideous problem.  Are the names merely nationalistic pride or do
they merely represent different datums/prime-meridians or are they
computationally different?  From my point of view I am only concerned
about how they are computed and leave datums/prim-meridians to others.

+tmerc in the libproj library uses the equation set based upon
Thomas' "Conformal Projections ..." page 97.  This version has a
few more terms than Snyder's Working Manual, page 61. I take it that
the Boaga-Gauss has elided a few more terms.

The question now becomes should I add another version of tmerc
with the truncated evaluation similar to what was done with the
French version of the conformal conic?  And call this the "boaga"

The following is copied from
and is basically a copy of Snyder's version.
Easting, E =  FE + k0*[A + (1 - T + C)A3/6 + (5 - 18T + T2 + 72C -
Northing, N =  FN + k0{M - M0 + *tan*[A2/2 + (5 - T + 9C + 4C2)A4/24 + 
	(61 - 58T + T2 + 600C - 330e'2)A6/720]}
This is lumped with other discussions that include the Boaga projection
and thus implying that it defines the Boaga projection.

Is this true??

Thank-you from confused on Cape Cod.

On Tue, 2003-04-29 at 11:38, Clifford J Mugnier wrote:
> Gauss-Boaga is a specific truncation and has characteristic distortion that
> is masked by inadvertent substitution with Gauss-Kruger.  For
> survey-quality work it DOES make a difference.  For 1:50,000-scale GIS work
> it does not make a difference on land - it does offshore.

PROJ.4 Discussion List
See http://www.remotesensing.org/proj for subscription, unsubscription
and other information.

More information about the Proj mailing list