[Proj] Question about Italian conversion

[Markus Neteler]

On Dec 29, 2007 8:54 PM, Frank Warmerdam <warmerdam at pobox.com> wrote:
> massimo at studiodemarchi.net wrote:
> >
> >>> What am I doing wrong?
> >> Trying to follow the procedure with independent software, I get the
> >> impression that you didn't transform the datum from Hayford to WGS84.
> >> You simply inverse projected from x,y to lon,lat with the proper transverse
> >> mercator projection.
> >> With the Roma40 transform parameters found at <http://crs.bkg.bund.de>
> >> I arrive at lat,lon:
> >> 45d 06m 55.252s,  10d 47m 39.415s
> >> assuming a position vector rotation model (ISO) and an initial height of 0.
> >> The proj/epsg definitions you mention don't contain any datum transform
> >> instructions.
> >>
>
> > Thanks for your answer. I tried to do a coordinate transform using the -s_srs
> > EPSG:3003 (or 26591) and -t_srs EPSG:4326 parameters. How can I add the
> > necessary datum transform? I checked the documentation amd the forum, but
> > didn't find a clue.
>
> Massimo,
>
> I followed Oscar's link to http://crs.bkg.bund.de but did not see any easily
> identifiable datum transformation parameters for the Monte Mario datum.

Here they are (extracted from GRASS GIS source code):

datum.table:rome40      "Monte_Mario"
international dx=-225     dy=-65      dz=9
datumtransform.table:rome40
"towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68" "Italy
(Peninsular Part)" "Accuracy 3-4m"
datumtransform.table:rome40
"towgs84=-168.6,-34.0,38.6,-0.374,-0.679,-1.379,-9.48" "Italy
(Sardinia)" "Accuracy 3-4m"
datumtransform.table:rome40
"towgs84=-50.2,-50.4,84.8,-0.690,-2.012,0.459,-28.08" "Italy (Sicily)"
"Accuracy 3-4m"

They were taken from http://crs.bkg.bund.de.

See also:
http://it.wikipedia.org/wiki/Proiezione_di_Gauss-Boaga

Hope this helps,
Markus