I don’t have ACES OF THE DEEP but I do own two or three authentic WWII
German charts with the grid system with code letters.

Jurgen Rohwer’s AXIS U-BOAT SUCCESSES 1939-45 (English title; don’t recall
without going home and looking what the ‘auf Deutsch’ version is
called) reproduces the world reference chart set where one can at least
look up the first two letters of an area. We have discussed this chart
system once or twice on MARHST in the past.

I asked if anyone had ever produced, or would be interested in producing,
a computer application (preferably Java) that would convert a grid square
co-ordinate to Lat/Long and back. I got some expressions of interest but
lost all the material when my hard disk died at the end of July 97…

At any rate, for those who aren’t clear on this, the Kriegsmarine issued
charts with a grid system superimposed on them. The grid had two-letter
designations for large squares, covering ocean & coastal areas. Each of
these large squares would be divided into 9 small squares, and each of
those into 9, down about 3 or 4 levels. The alpha code of each square
would comprise a position, and position reports and often log entries were
made in these coordinates rather than lat-long.

Without looking at an actual chart, this is an INCORRECT example for
location, but does show how the system worked:

FIrst two letters denote chart location: example : FH
Looking at Atlantic chart this turns out to be , say , by the west coast
of Africa. The next two letters area for example EC – E puts it into the
center square of the 9 sub-squares of square FH:
ABC
DEF
GHI
and C puts it in the northeast sub-sub-square of subsquare E…..

(Except that without looking at one of the charts to jog my memory, they
may use numbers instead of letters at one level)…

But that is the general idea. Obviously, there is some security in your
position and scouting reports even if they are in plain language, if the
enemy doesn’t have your charts with how to interpret this grid.

-Brooks