Blog GIS & Territories

The reference website for coordinate systems used during World War II is Thierry Arsicaud’s website : Notes on the “Modified British System” used on the European Theatre of Operations during the WWII.
In 1919, Great Britain adopted in its territory the “British System”, based on a Cassini-type map projection and the use of a grid designed to facilitate the reading of the coordinates of the designated points . This system was replaced in 1927 by the “ British Modified System”, more suited to cover large geographical areas and military operational use by land  or airlift forces.
This “British Modified” system was used during the second world war by the British and American armies by being extended to European, North African, the Near East and South East Asian operation theatres. The following figure , from Thierry Arsicaud’s website shows the areas corresponding to the projections in course during World War II.   

The South Italy projection is a secant Lambert projection ( only one standard parallel), which uses the ellipsoid Bessel 1847.

The South Italy projection management with ArcGIS

You will not find this projection in those available as standard with ArcGis.
Once the projection is created, it will be necessary to enter the transformation methods to the usual systems (WGS84, NTF, RGF93).

The parameters of the South Italy projection are the following:

False_Easting 700000.0
False_Northing 600000.0
Central_Meridian 14 E
Standard_Parallel_1 39 , 5 ° N
Scale_Factor 0.99906

In terms of the geodesic system, the parameters are :

Name: Bessel 1841
Angular Unit: Degrees
Prime Meridian: Greenwich
Datum: D_Bessel_1841
Spheroid: Bessel 1841
Semimajor Axis: 6377397.155
Semiminor Axis: 6356078.963
Inverse Flattening: 299.1521535
Click on the following link to download a file . prj with all the necessary definitions.

[ dg ids = “2428”] To move this projection to the data block or to a GIS layer, open the coordinate systems definition window and click on the import button:   

How to set up transformations in ArcMap

The transformation of Bessel datum 1841 to NTF or RGF93 is done through a three- parameter transformation dX , dY, dZ .

The values to go from Bessel to NTF are :

dX = 850,

dY = -143 and

dZ = 160

The values to change from Bessel to RGF93 or WGS84 are :

dX = 682,

dY = -203 and

dZ = 480

To set up the transformation of this geodesic system towards the one you usually use :

1-Open a new project in ArcMap
2-Load a layer in the usual projection system (Lambert 93 or Lambert I , II, II, IV , or extended II )
3-Load a map in South Italy projection

You will notice that a window appears, indicating you that the geodetic systems are different and which proposes you to set up a transformation.

4-Click the Transformations button If you are working with Lambert I, II, II, IV or II extended

5-Make sure that in Convertlater  you have Bessel_1841
6-That in To , you have well GCS_NTF
7-Click on New

8- In Name type Bessel_NTF
9-In settings enter the values 850, -143 and 160 for, respectively, X, Y, Z.
10-Click OK , and OK

Next time you have to perform a transformation, you will find this transformation in the drop down list.

The management of the South Italy projection with QGis

Similarly as with QGis, the transformations are performed automatically (provided that you inform the ellipsoids ), it is much simpler to manage this projection than with ArcGis. To define a new coordinate system Custom , click the Preferences menu ->CustomProjection…

In Name enter South Italy

In settings enter the proj4 definition of the projection:

+ proj = lcc + lat_0 = 39.5 + lat_1 = 39.5 + lon_0 = 14 + k_0 = 0.99906 + x_0 = 700000 + y_0 = 600000 + ellps = bessel + units = m + no_defs

Click OK.
And, now you can work with the South Italy projection and overlay data in this projection with data depicting other projections.

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Atilio Francois