45:), each with its unique two-letter designation (e.g. AE, AF, BA, BB, etc.) with each square called a quadrant 486 nautical miles to a side. E.g CA covered the East Coast of the United States from about Portsmouth, Hampshire south to Cape Fear, North Carolina. Each such sector was further sub-divided into a 3 x 3 matrix, so that there were nine squares. Each of the nine squares were again divided into nine smaller squares.
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This was known as a Grid, so that there were now 81 total grid squares within a sector. Each grid was given a two-digit designation, so the Grid System would now have two alphabets and two digits. Each of these Grids were again divided in the same manner – first into a 3 x 3 matrix, and then each
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Thus instead of transmitting the actual patrol zone, they would use an offset, so that any zone that was transmitted over the waves would be an offset of a secret location. This secret location was changed at random intervals, and U-boat captains would calculate the new patrol zone based on the
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matrix was divided into nine squares, so that a further 81 squares were formed within the Grid. Each newly formed square was again given a two digit designation. The complete Grid System would now read as two alphabets with four digits. This can be referred to as the patrol zone. Thus the
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could pinpoint any location on the globe using six characters, a very useful tool when using radio. Its precision was to the level of six nautical miles within a grid. This was how locations were communicated to naval units, particularly
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As the war advanced, the
Germans suspected that the Allies were deciphering their patrol reports. As a precautionary measure they transmitted patrol zones by using coded sectors.
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The reference used in the ’Gradnetzmeldeverfahren’ can be viewed as a short form of the position in full, without a real translation or encoding.
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For example, major grid AJ is located south of
Greenland. Each submarine was equipped with an Adressbuch to decipher the locations.
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version, the entire globe was divided into large square sectors (assuming a
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Ultra in the
Atlantic: The German Naval Grid and Its Ciphers
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95:"The War in Maps - The Grid system"
93:Helgason, GuĂ°mundur (1995-01-01).
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141:, Aegean Park Printers, 1996,
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162:Geographic coordinate systems
17:German Naval Grid Reference
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124:"Naval Grid Calculator"
99:Encyclopedia of Things
21:Gradnetzmeldeverfahren
43:Mercator projection
137:Bray, Jeffrey K.
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101:. uboat.net
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105:2016-05-03
80:References
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25:Luftwaffe
76:offset.
60:Scotland
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56:U-boats
37:In the
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