Description of the ’Gradnetzmeldeverfahren’
The idea behind the ’Gradnetzmeldeverfahren’ was to develop a system where bases and
navigation points could be given a position both in maps prepared by the armed forces but also other
available maps. It was based on the Greenwich system, which describe a given position by longitude
and latitude, measured in degrees. This meant that the system could be used on all maps, which were
made utilizing the widespread Greenwich geographic coordinate system, regardless of scale or
projection used when preparing the map.
The numbers used to give the position of a certain location using the
’Gradnetzmeldeverfahren’ can be viewed as a short form of the position in full,
without a real translation or encoding. The basic division have its base at the 0°-meridian
(Greenwich), and have division lines at every 10° longitude. The areas between every tenth degree
longitude are limited to the north and south by the 89°, 79°, 69°, 59°…and so on degree
latitude. These areas, which are limited by sides measuring ten degrees longitude and
latitude are called ’Zusatzzahlgebiete’.
The ’Zusatzzahlgebiete’
Every ’Zusatzzahl’ therefore describe an area contained within every tenth degree longitude and
latitude. The basis for the latitudinal description of the border of the
’Zusatzzahlgebiet’ is
1° southern latitude (1° south of Equator) with a division line on every tenth degree northern
and southern latitude. The corresponding basis for the longitudinal description is the
Greenwich 0°-meridian, with division lines on every tenth degree eastern and western longitude.
The ’Zusatzzahl’ are given by the ten-count of the northwestern corner of each
’Zusatzzahlgebiet’. The first number give the ten-count of the longitude, while
the second number give the ten-count of the latitude. If the degree number is below 10°, a zero is
used. The repetition of the ’Zusatzzahl’ in the four quarters of the globe, make
the use of a special description necessary; north of 1° southern latitude the
’Zusatzzahl’ for the areas having eastern longitude are given the additional
description ’Ost’, while the areas having western longitude have the addition
’West’. South of 1° southern latitude the ’Zusatzzahl’ for the areas
having eastern longitude are given the additional description ’Südost’, while the areas
having western longitude have the addition ’Südwest’.
The ’Großtrapez’
The subdivision of the ’Zusatzzahlgebiete’ follow every whole degree longitude and latitude.
The area between two neighboring degrees latitude and longitude are called a ’Großtrapez’,
which can be further subdivided given the needed degree of accuracy. The 100 ’Großtrapeze’
included in one ’Zusatzzahlgebiet’ are given numbers ranging from
’00’ to ’99’.
Be aware of the
different numbering system for areas west and east of the Greenwich 0°-meridian.
The size of a ’Großtrapeze’ is approximately 70x111 kilometers (in Germany and other areas
with the same latitudinal width).
The two-digit numbering are calculated in the following way: Using the northwestern corner of
the ’Zusatzzahlgebiet’ as basis, the first number is defined by the one-count of the
geographical longitude (numbers on the upper and lower edge of the map), while the second number
is defined by the one-count of the geographical latitude (numbers on the left and right edge of
the map).
Subdividing the ’Großtrapez’:
The ’Mitteltrapez’
The first subdivision of the ’Großtrapez’ is the ’Mitteltrapez’,
which have an area of approximately 35x28 kilometers. Using the latitudinal parallels at
15’, 30’ and 45’ and the longitudinal meridian at 30’, every ’Großtrapez’ are
divided into eight ’Mitteltrapeze’.
The ’Mitteltrapeze’ are numbered from ’1’ through ’8’
starting with the area in the upper left corner and ending with the lower right one.
The ’Kleintrapez’
The second subdivision define the ’Kleintrapeze’ measuring approximately 9x11 kilometers.
The latitudinal parallels with 5’ distance between them and the longitudinal parallels 10’ apart,
divide the ’Mitteltrapez’ into nine ’Kleintrapeze’.
The numbering of the ’Kleintrapeze’ run from ’1’ through ’9’,
starting in the upper left corner, making three rows of ’Kleintrapeze’, with the ninth positioned in the lower right corner of the ’Mitteltrapez’.
The ’Meldetrapez’
The third subdivision is called ’Meldetrapeze’ and have an area of approximately 3x4 kilometers.
The latitudinal parallels positioned at 1’40”, 3’20”, 6’40” and 8’20” and the longitudinal parallels
positioned at 3’20” and 6’40” divide the ’Kleintrapez’ into nine ’Meldetrapeze’.
The size of the resulting ’Meldetrapez’ was usually small enough as to give the necessary degree
of accuracy for the report of a given position.
The numbering of the ’Meldetrapeze’ run from ’1’ through ’9’, starting in the
upper left corner, making three rows of ’Meldetrapeze’, with the ninth positioned in the
lower right corner of the ’Kleintrapez’.
In the system used until 30. April 1943, there were only four ’Meldetrapeze’ in a
’Kleintrapez’, numbered from ’1’ through ’4’.
The ’Arbeitstrapez’
The fourth subdivision results in the definition of an ’Arbeitstrapez’ with an area of
approximately 1x1,2 kilometers by a further subdivision by a factor three the distance between
the parallels in the ’Meldetrapez’. The description of the ’Arbeitstrapeze’ are given
by small letters from ’a’ through ’i’, running in three rows starting in the upper
left corner of the ’Meldetrapez’. In the old system, there were only four
’Arbeitstrapeze’ named ’links oben’ (lo), ’rechts oben’ (ro),
’links unten’ (lu) and finally ’rechts unten’ (ru).
’Jägermeldenetz’
For the guidance of fighter aircraft, anti-aircraft artillery and early warning systems,
another system was also in use by the Luftwaffe. In the ’Jägermeldenetz’,
the ’Zusatzzahlgebiete’ were divided in a northern and a southern part, these
subdivisions called ’Jagdtrapeze’. As an example, the ’Zusatzzahlgebiet’
’05 Ost’ would be subdivided into the ’Jagdtrapeze’ ’05 Ost Nord’
and ’05 Ost Süd’. The subdivision of the ’Jagdtrapeze’ was made using the
same system as on the ’Großtrapeze’, dividing along whole degrees latitude and longitude.
The ’Mitteltrapeze’ was given other descriptions, not two numbers but two upper letters.
Starting in the northwestern corner running in rows from west to east and north to south,
the descriptions started with ’AA’, ’AB’, ’AC’ and
so on until ’AU’,
then ’BA’, ’BB’ all the way through to ’UU’. The double
letter areas
cover the whole ’Jagdtrapez’, without regard to the ’Großtrapez’.
One important addition: The letter ’I’ is not used in the annotation!!!!
This caused one of my research friends a considerate headache, when trying to test my example below!!!
