The reference used in the ’Gradnetzmeldeverfahren’ can be viewed as a short form of the position in full, without a real translation or encoding.
In the Kriegsmarine version,[1] the entire globe was divided into large square sectors (assuming a Mercator projection), each with its unique two-letter designation (e.g. AE, AF, BA, BB, etc.)
E.g CA covered the East Coast of the United States from about Portsmouth, Hampshire south to Cape Fear, North Carolina.
As the war advanced, the Germans suspected that the Allies were deciphering their patrol reports.
This secret location was changed at random intervals, and U-boat captains would calculate the new patrol zone based on the offset.