[Proj] Italian Datum

[Jan Hartmann]

Yes, this works. Thanks Mikael.

Jan

On 1/25/2013 2:08 PM, Mikael Rittri wrote:
> Hello Jan,
> I would think it is EPSG:4806, "Monte Mario (Rome)".
> If you use
>
>     +init=epsg:4806
>
> this would expand to
>
> +proj=longlat +ellps=intl +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68 +pm=rome +no_defs<>
>
> (at least in Proj 4.8.0). The datum shift is intended for the
> Italy mainland, and has accuracy 4 meters. There are other
> published datum shifts designed for Sicily and Sardinia,
> also with 4-meter accuracy, but if I recall correctly they
> don't disagree by more than about 5 meters from the mainland
> datum shift.
>      And there are several datum shifts for offshore areas
> around Italy; I haven't compared them with the mainland
> datum shift.
>
> For a map in scale 1:100000, I think the mainland datum shift
> should be okay for the entire Monte Mario area.
>
> Off-topic: Since about Christmas, I only get a small random
> subset of the Proj mails to my e-mail account. I don't
> think it is due to my spam filter or wrong subscription
> settings.
>      Am I the only one with this problem?
>
> Best regards,
>
> Mikael Rittri
> Carmenta
> Sweden
> http://www.carmenta.com
>
> -------- Original Message ---------
> Jan Hartmann j.l.h.hartmann at uva.nl
> Fri Jan 25 06:49:24 EST 2013
> ________________________________________
> Hi all,
>
> I'm indexing an Italian map series 1:100.000, published around 1950 on
> the basis of measurements in the first half of the 20th century. Map
> sheets are registered in lat-lon values, 30 seconds east-west 20 seconds
> north east, with Rome as central meridian (12d27'08''40). Those values
> are on the International Ellipsoid. I would like to transform those
> values to WGS84. In the Proj4 epsg file I find lots of latlon
> projections with ellps=intl and different +towgs84 parameters. I read
> Cliff Mugnier's column about Italy
> (http://www.asprs.org/a/resources/grids/08-2005-italy.pdf), but I am
> unable to find which epsg number is most appropriate for these maps. Can
> anyone help?
>
> Jan
>