[OSRS-PROJ] Projection of historic maps WW II - Italy

Markus Neteler neteler at itc.it
Fri Jun 6 14:08:33 EDT 2003

On Fri, Jun 06, 2003 at 11:29:53AM -0500, Clifford J Mugnier wrote:
> Markus,
> The Bessel 1841 parameters you listed are correct.  The Monte Mario Datum
> of 1875 is not going to be significantly different from the current Monte
> Mario Datum of 1940.  The Istituto Geografico Militare occasionally "lets
> out" datum shift parameters from their national datum to WGS84, but the
> parameters vary considerably from one region of Italy to another.  They are
> the only RELIABLE source of such transformation parameters.
> The projection parameters you list are correct, but the scale factor at
> origin is 0.998992911

Thanks for the quick answer! The changed scale factor moves the map
into another direction now - there is still some hundred meters of
deviation. I will have to "play" with the towgs84 parameter.

> If you obtain some reliable datum shift parameters, please share them with
> the list including your source and the area for which they are applicable.

Here are some (you may know them already):

# http://crs.ifag.de/
rome40  "towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68" "Italy (Peninsular Part)" "Accuracy 3-4m"
rome40  "towgs84=-168.6,-34.0,-34.0,-0.374,-0.679,-1.379,-9.48" "Italy (Sardinia)" "Accuracy 3-4m"
rome40  "towgs84=-50.2,-50.4,84.8,-0.690,-2.012,0.459,-28.08" "Italy (Sicily)" "Accuracy 3-4m"

Kind regards

 Markus Neteler
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