I'm trying to georeference some WWII maps available at the University of Texas repository (e.g., example map).
The problem is that these maps refer to an unknown proj system (at least for me) and I can not figure out how to set up a custom reference system.
These maps refer to a "Mediterranean Grid" and "Caucasus Grid" as follow:
Is anybody aware of how to manage these kinds of grid systems and how to create a custom projection (and a graticule) on top of them?
In one of the adjoining map sheets, I found the following information:
It introduces new clues and allows the benefiting of this discussion: Setting proj parameters of old map.
EDIT April 5th:
On the basis of the different answers (thanks to all), I was able to generate the following custom projection:
+proj=lcc +ellps=clrk80 +lat_0=39.50 +lon_0=45 +lat_1=39.50 +x_0=2155500 +y_0=675000 +units=m +no_defs
Then I georeferenced this sheet. I tried either with Helmert or Polynomial or Thin Plate Spline transformation algorithm (with just few differences). Yet, the map appears inaccurately georeferenced. See the following example:
curl -L "http://legacy.lib.utexas.edu/maps/ams/turkey/txu-pclmaps-oclc-10127923-palu-e14.jpg" > ./output.jpg # add control points gdal_translate -of GTiff -gcp 751.581 2077.58 1.72e+06 600000 -gcp 6302.39 1037.18 1.81e+06 600000 -gcp 6510.44 5478.53 1.8e+06 530000 -gcp 1461.03 5785.78 1.72e+06 540000 ./output.jpg ./output_gcp.tif # apply the proj parameters gdalwarp -r near -tps -co COMPRESS=PACKBITS -t_srs "+proj=lcc +ellps=clrk80 +lat_0=39.50 +lon_0=45 +lat_1=39.50 +x_0=2155500 +y_0=675000 +units=m +no_defs" ./output_gcp.tif ./output_mm_warped.tif
I'm afraid that, as suggested by @GabrielDeLuca, the missing of datum transformation is a big issue. But I have no idea how to collect this missing piece of the puzzle.
In addition, whereas other sheets of the same series report also the scale factor (see for instance the Levant Grid parameters below), to my knowledge, there are no maps of Caucasus Grid that offer this information.