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

[Gerald I. Evenden]

The biggest problem for me is the lack of complete information.

1. Italian IGM series? Old or new?  Are they based on UTM?

2. What are the specific geographic coordinates being projected
	and the x-y of the results.  What do you feel they should be?

3. Correcting the longitude of Rome by hand?  Mighty big area to define
	by one point.

4. The "PS" specification is incompleat and possibly redundant but
	Sorry, I can't read Italian so my "translation" may be
	suspect but there seems to be two central
	meridians.  I would guess that "Ovest" and "Est" are west
	and east but no mention of north or south.  Similarly, two
	false westings and eastings?  The description seems incomplete.

Lastly, the zone number of 32 is a little suspect and I would have
chosen zone=33 which would put Roma closer to the central meridian.
Lon 12 is the dividing line between zone 32 and 33.

The following script:
./lproj +proj=utm +zone=32 +ellps=intl <<EOF
12d37E 41d52N
EOF
./lproj +proj=utm +zone=33 +ellps=intl <<EOF
12d37E 41d52N
EOF

produces the results:

800183.96       4641382.04
302191.13       4637801.10

On Tue, 2003-04-29 at 03:45, Bud P. Bruegger wrote:
> Hello everyone,
> 
> I hope someone can help me with what should probably be an easy
> question.
> 
> For an old series Italian IGM 1:25,000 map, I try to project the map
> corners (whose lat/long is known) to UTM (as used in the map).  
> 
> I naively tried the following:
> 
> proj +proj=utm +zone=32 +ellps=intl
> 
> and corrected the longitude by hand for the meridian of Rome
> (12d27'8.4"E).  But the UTM coordinates that come out don't seem to
> be correct.  Any idea what I'm doing wrong and how the projection
> should be defined?
> 
> Also, if anyone has a numeric example handy for testing...
> 
> Many thanks for any help I can get!
> 
> --bud
> 
> PS.  I found the following information that is probably for the new
> series IGM that may shed more light on my problem:
> 
>  Transverse_Mercator (ARC/INFO keyword: TRANSVERSE)
>  Unità di Distanza Planare: METRI (ARC/INFO keyword: METERS)
>  Fattore di scala al meridiano centrale: 0.99960
>  Longitudine del meridiano centrale: -3°27'08.4'' per il fuso Ovest / 
>                                      +2°32'51.6'' per il fuso Est
>  Falso est: 1500000 per il fuso Ovest /
>             2520000 per il fuso Est
>  Nome del Datum: MOD
>  Nome dell'Ellissoide: INTERNATIONAL1909
> 
> 
> /-----------------------------------------------------------------
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