British Army Middle East Map Reference Point Code

MIDDLE EAST MAP REFERENCE POINT CODE

The British Army Map Reference Point Code was a method of sending disguised map coordinates in a plain text communication when no other cipher or code was used. From 1st December 1943, the whole of the British Army adopted a standard system based on the one being used by forces in the Middle East.

Below is an order by 21st Army Group implementing the Map Reference code and with instructions on its use.

 

SECRET

SUBJECT Map Reference Point Code

21 A Gp/196/1/Ops

1. It has been decided to adopt a standard Map Reference Code for use throughout the Army. The object of this is to ensure the smooth and rapid cooperation of formations transferred from one theatre to another or between forces of different theatres which effect a junction during operations.

2. Consequently, with effect from 1st December, 1943, a Map Reference Code on the lines of the Middle East Map Reference Point Code is becoming standard throughout the Army both at home and abroad.

3. This Code will be adopted throughout 21 Army Group with effect from 1st December, 1943.

4. Details of the Code and an explanation of its operation are given at Appendix 'A'.

5. The general principles which will be observed when using the Code are given at Appendix 'B'.

6. Responsibilities for issue of the Code are shown at Appendix 'C'.

7. Sufficient copies are forwarded for distribution down to units.

HQ 21 Army Group,
No. 1 APDC,
LONDON, W.1.
16 November, 1943.

 

SECRET
APPENDIX 'A' to
21 A Gp/196/1/Ops
dated 16 November, 1943.

METHOD OF USING MAP REFERENCE POINT CODE

1. This system uses the map grid with the following modifications:-

(a) Horizontal and vertical coordinates are read from pre-arranged reference points at grid intersections.

(b) Horizontal coordinates may be read to the East or to the West of a reference point; the vertical coordinate to the North or the South of it.

2. Three-figure coordinates are used, a coordinate of 100 being equal to 10 Kms. (e.g. a coordinate of 363 represents a distance of 36.3 Kms: 049 represents 4.9 Kms).

3. The operational area is divided into a convenient number of sub-areas, lettered A, B, C, etc.

4. In these sub-areas reference points are chosen, marked on the map and lettered. These are used as origins from which coordinates are counted. The points and the system of lettering must not conform to a regular pattern or order and each point must be at a grid intersection. Letters allotted to reference points are changed weekly and a new set of reference points is introduced at irregular intervals of about one month. The letters allotted to sub-areas are changed when reference points are changed. An immediate complete change is made in the event of compromise.

5. It is necessary, when giving the map reference of a point to indicate its approximate direction from the reference point used. For this purpose the cardinal points, North, East, South, West are used encoded in that order on a four-letter combination which is changed daily; e.g.

NESW
DGRK

6. The reference of a point is indicated by giving, in the order shown:-

(a) The letter of the sub-area in which the chosen reference point is situated.

(b) The letter of the reference point chosen as the origin.

(c) The cardinal points code letter signifying East or West of the reference point.

(d) Its horizontal coordinate counting East or West as necessary from the reference point.

(e) The cardinal points code letter signifying North or South of the reference point.

(f) Its vertical coordinate counting North or South as necessary from the reference point.

Care will be taken not to choose a reference point which will produce a coordinate 000 either horizontally or vertically. Apart from this, any reference point may be chosen.

7. Examples are given in the diagram below which is a portion of sub-area C.

DIAGRAM
(Each small square has 1 Km sides)

British Army Map Reference Point Code

 

Point H is at 870720
Point L is at 930650

Cardinal Point Code
N E S W
D G R K

Map reference of point 1 is, CHG102R048 (reference point "H") or CLG042D022 (reference point "L").

8. A point is identified from its map reference by:-

(a) Finding the given reference point in the sub-area concerned.

(b) Identifying the approximate direction of the point from the reference point.

(c) Using the coordinates to identify the position of the point.

 

 

 

SECRET

APPENDIX 'B' to
21 A Gp/196/1/Ops
dated 16 November, 1943.

PRINCIPLES TO BE OBSERVED WHEN USING THE MAP REFERENCE POINT CODE

1. It must be clearly understood by all users that the security of any map reference code which it is practicable to use under field conditions cannot be very high. It is therefore important that in active operations changes of sub-area letters, reference points, reference point letters and cardinal point codes are made as frequently as shown in Appendix 'C', para 6.

2. The following general principles will be observed when using the Map Reference Point Code:-

(a) The Map Reference Point Code will be used in written messages when it is desired temporarily to conceal from the enemy a location indicated by a map reference. It will also be used for RT and key conversations in those theatres where an RT code is not in use.

(b) When an encoded map reference is used, it is strictly forbidden to mention the feature or place on the map which it represents.

(c) Map references will not be encoded when they refer to enemy locations.

(d) Map references will not be encoded when the message is sent in cipher.

(e) Any map reference occurring in a conversation or message which is encoded in SLIDEX or any other RT code will be encoded in the RT code concerned. SLIDEX and the Map Reference Point Code will not be used in the same conversation or message.

 

 

SECRET

APPENDIX 'C' to
21 A Gp/196/1/Ops
dated 16 November, 1943.

METHOD OF ISSUE OF MAP REFERENCE POINT CODE

1. HQ Army Group will issue the cardinal point code to be used daily by fmns [formations] in paras 2, 3, and 6 below.

2. Headquarters of Armies, independent Corps and independent Divs will:-

(a) Allot and letter sub-areas for the area in which they and formations under their command are liable to operate.

(b) Choose 26 reference points in this area.

(c) Issue sets of letters for these reference points and the dates on which they are to be changed.

(d) Extract cardinal point code from list issued by Army Group.

(This code is for use back to Army Group and within the formations concerned down to divisional level.)

3. Each Div HQ will use the sub-area letters allotted in 2(a) above and:-

(a) Choose 26 reference points in the area within which they are operating.

(b) Issue sets of letters for these reference points and the dates on which they are to be changed.

(c) Extract cardinal point code from list issued by Army Group.

(This code is for use within Div).

4. (a) In communications to any other div in the same Army, the code allotted by Army will be used. For communications between divs not of the same Army, the code will be passed between the divs concerned by direct liaison. Each div will use its own Army or Corps code for communications in such cases.

(b) Copies of each div code will be given to each Corps, Army and Army Group HQ on a scale as demanded by these HQs. In the case of HQ 21 Army Group three copies are required. These higher formations must bear in mind the need of the "J" Service.

(c) In order to localize the effect of compromise by capture, lower formations will not be issued by the higher formations specified in paras 2 and 3 above with more reference points than are necessary to cover their area of operations. All users must, however, have a choice of at least six reference points from which to work.

(d) The cardinal points code may be issued to cover any period up to one month, but formations and units below div HQs will not hold the code for more than seven days in advance.

5. Each Command of Home Forces has a Map Reference Point Code of this type. Every formation will make itself acquainted with the code of the Command in which it is serving and use it for communications to that Command if necessary.

6. Independent brigades or units not catered for in the above instructions will issue their own Map Reference Point Code as in para 3 above using the sub-area(s) allotted by the Command within which they are situated.

7. The following is a summary of the frequency of change in the Map Reference Point Code.

(a) Sub-area letters will be changed at irregular intervals of approximately one month.

(b) Sets of reference points will be changed at irregular intervals of approximately one month.

(c) Letters allotted to reference points will be changed weekly.

(d) Cardinal point code will be changed daily.

(e) In the event of compromise a complete change will be made in all parts of the code.

 

[Source: TNA WO 199/306, transcribed by www.arcre.com ]