We have discussed in previous articles in depth how to access the allies’ cartography during WWII (1939-45) at the library of the University of Texas ( http://www.lib.utexas.edu/maps ). In this article we will discuss how to access and use the maps created by the General Staff of the German Armies in view of the invasion of England, on the site of David Rumsey Map Collection . You can access free of charge some 70,000 documents. I let you discover for yourself the geographical and historical scope of this impressive content.
Let’s analyse here a tiny part, scanning the base map of the German Army during World War II (2800 documents) and how to integrate it in your preferred GIS (ArcGis or QGis).
Access to documents
Go to http://www.davidrumsey.com/luna/servlet/view/all and start by registering. Do not panic, you enter a name, a password, an email address, and that’s done . No confirmation email or other data to provide.
On the left banner, you can click to select a part of the collection.
If you click on Generalstab des Heeres you will have the subset corresponding to the Military High Command (2824 documents):
Now if you click on another element (the banner has been updated according to your selection ), for example Military, you will only have 155 military maps within Generalstab des Heeres documents. And so on: if you click on Leeds, you will only have maps of the city of Leeds.
So much for navigation. Now, to recover the corresponding raster, for example for the city of Sunderland:
Click the Export button
Select the largest definition. A message tells you to wait …
Then the file is available for downloading . Do not forget to change the default in Save the file …
And, your file is available in your download directory.
However, the image is not georeferenced. To be able to integrate the image in your GIS you have to georeference from the grids present on a map. But first, you have to define the coordinate system.
The Gauss-Kruger 3 degrees system
For any information, you have this framed on the map:
Translation : Gauss- Krugger mesh zone 119.
The Gauss- Krugger projection is similar to the UTM projection. However, it can have time zones from 3 or 6 ° of amplitude. During the Second World War, Germany used the 3 ° time zones.
Here is a small synthetic table of 3 ° time zones for Europe :
The top line gives the central meridian of the zone, the line below the zone number.
Among the available maps you will find maps made with the time zone 119 and the time zone 0.
The parameters for the time zone 119 are
For the time zone 0, you have to replace the “central meridian : 357.0” with 0.
This is for the projection. Now let’s deal with the ellipsoid. This information is not provided in the maps, but I give it to you: Bessel 1841
The parameters of this ellipsoid are
- a = 6,377,397.155 m
- f = 1 / 299,152 815 351 323 3 (0.003 342 773 154 ± 0.000 005)
- b = 6,356,078.963 m
Last problem, the geodesic system. The geodesic system used is the German triangulation. To transform this triangulation into WGS84, we must transform 3 parameters
delta X = 631
delta Y = 27
delta Z = 446
As expected, the average processing error is approximately 20m. Do you do not expect miracles. With the folds of the paper cards and other sources of error, it is likely to get a hundred meters of difference .
Gauss-Kruger 3 degrees projection with ArcGis
Projection files do not exist by default in ArcGis. We need to create them.
Right click on the data block, open the Properties window, tab coordinate system.
Click the Add Coordinate System -> New -> coordinate systems projected
Give a meaningful name with the time zone number, select Gauss Kruger (Or Universal Transverse Mercator) in the list of projections, and enter 500,000 as False_easting and 357 as Central_Meridian for the time zone 119 and 0 if you enter the parameters of time zone 0.
Click the Edit … button
and select the system Deutsches Hauptdreiecksnetz ( German triangulation network ).
Click OK and OK.
Your document is ready to georeference your image.
Load the image in ArcMap and activate the toolbar “georeferencing” if this is not already done. Click OK on the warning message for the absence of coordinate system.
You will return at least four points, in the four corners of the map, at the crossroads of the map’s grid.
For the upper left corner, for example, click on the tool “add a calibration point” of the “georeferencing” toolbar, then click on the crossing of the lines on the map and click with the right button. A window opens to enter manually the XY coordinates.
For X the coordinates, the map’s label reads 119600. This figure is broken down in two parts: the first 119 is the number of the time zone, the second 600, is the X coordinate of the point, in km. As we work with units in meters you must make the following transformation 600km to m = 600000.
in the case of the Y coordinates , the labels are expressed in km. Here 6089. We return this value in m: 6089000.
Repeat this operation with the other 3 points. Then, in the georeferencing toolbar, from the drop-down menu, click Rectify to create a new georeferenced image in tif format.
Now you can load this image in your different projects. When you perform this task, since the geodesic system is different from the one of your projects (WGS84 or assimilated), a warning message will appear.
Click on the button “transformations” to enter the transformation parameters between the Deutsches Hauptdreiecksnetz and the GCS WGS84 system
Click on New, and then enter the three parameters of the geocentric transformation : 631, 27, and 446. Then OK and OK.
Your image is displayed now in your document and is superimposed on the current layers.
Gauss-Kruger 3 degrees projection with QGis
Using QGis, the projection management is much simpler. Just create your custom projection that contains all elements: projection, geodesic system, transformation.
Before loading or georeferencing your image, create your two custom projections for the 0 and 119 time zones.
Click Preferences -> Custom Projection menu
Click the + button to add a new projection.
In the field name enter, for example, Gauss_kruger_3degres_119 for the time zone 119.
In the Settings field, return
+ Proj = tmerc + lat_0 = 0 + lon_0 = 357 + k = 1 + x 0 = 500000 + Y_0 = 0 + = ellps bessel + units = m + no_defs + towgs84 = 631,27,446,0,0,0,0
Repeat the operation for the time zone 0 in returning Gauss_kruger_3degres_0 for the name and
+ Proj = tmerc + lat_0 lon_0 = 0 + = 0 + k = 1 + x 0 = 500000 + Y_0 = 0 + = ellps bessel + units = m + no_defs + towgs84 = 631,27,446,0,0,0,0
for the parameters .
It’s ready! You can load your georeferenced image or open the Referencing tool (Raster -> georeferencing -> geo-reference)
Indicate the projection to use (one of the two that you just created) and return the same four control points as those we have seen above with ArcMap.