[OSRS-PROJ] cs2cs question: Gauss-Boaga

[Markus Neteler]

Dear list,

sorry for a sort of "newbie" question: Today I tried to
investigate if cs2cs does datum transformation for
the Italian Gauss-Boaga system:

[btw: there is no +towgs84 present for the Gauss-Boaga related 
EPSG code 26591 in nad/epsg, any reason for that?]

I struggled here: While this is doing calculations:

cs2cs -v +proj=latlong +datum=WGS84 +to +init=epsg:26591 +towgs84=-225,-65,9
# ---- From Coordinate System ----
#Lat/long (Geodetic)
#
# +proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
# ---- To Coordinate System ----
#Transverse Mercator
#       Cyl, Sph&Ell
# +init=epsg:26591 +towgs84=-225,-65,9 +proj=tmerc +lat_0=0.000000000
# +lon_0=9.000000000 +k=0.999600 +x_0=1500000.000 +y_0=0.000 +ellps=intl
# +units=m +no_defs

the next lines don't: 
cs2cs -v +proj=latlong +datum=wgs84 +ellps=WGS84 +towgs84=0,0,0 \
  +to +towgs84=-225,-65,9 +proj=tmerc +lat_0=0.0 \
  +lon_0=9.0 +k=0.999600 +x_0=1500000.000 +y_0=0.000 +ellps=intl \
  +units=m +no_defs
Using from definition: proj=latlong datum=wgs84 ellps=WGS84 towgs84=0,0,0
Rel. 4.4.5, 9 January 2002
<cs2cs>:
projection initialization failure
cause: unknown elliptical parameter name
program abnormally terminated


...although both should be the same (or not?). Beside that I would like
to know if I am right in my assumption, that this "cs2cs" with additional
+towgs84 parameter is the way to reproject from lat/long to Gauss-Boaga
*with* datum transformation from WGS84 to Rome40. Say, at least with
less error than using the 'proj' command?

Thanks for comment,

 Markus

-- 
Markus Neteler

ITC-irst, Istituto per la Ricerca Scientifica e Tecnologica
     Project on Predictive Models for the Environment    
Via Sommarive, 18        -      38050 Povo (Trento), Italia
tel +39 0461 314 -520 (fax -591)          http://mpa.itc.it
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