APPENDIX II
The Germans conducted the Normandy campaign using maps developed from pre-war French examples, which used hachure (shading) to give an impression of elevations. The British used much better, contour maps of France. These were prepared using a combination of earlier French cartography and aerial photographs interpreted with stereoscopic viewers. This was quite a remarkable achievement, considering that the first contour maps of the land were produced without access to the enemy-held territory being mapped; the British Army Geographical Section coyly printed on their maps of enemy-occupied Normandy, ‘not been checked on the ground’.
All map references given in this text refer to the standard British Army 1:25,000 tactical map. British map references were generally given in six figures, to indicate a precise location, or in four figures indicating a map square (measuring 4cm, representing a square kilometre).
In a four-figure reference, the first two digits indicate the longitude, and so correspond with the matching pair of digits on the south edge of the map. The third and fourth digits are latitude, matched with a pair on the west map edge. Tracing the indicated lines of longitude and latitude to their intersection, the crossing point is the south-west corner of the indicated map square. Thus, ‘1064’ indicates the map square containing the town of Cagny.
In a six-figure reference, the first two digits similarly indicate the line of longitude (as numbered along the horizontal edges of the map). The third digit indicates the precise ‘easting’, the distance in hundreds of metres to the east (‘right’) of the ruled line. Likewise, the fourth and fifth digits indicate the line of latitude (as numbered along the vertical edges of the map), and the sixth digit the precise ‘northing’ in hundreds of metres to the north (‘above’) the ruled line. Having plotted the coordinates, the point at which they intersect is the map reference. So, ‘109643’ approximates the location of Cagny church. Estimating hundreds of metres (or tenths of a kilometre ‘box’) comes quite easily with a little practice: until familiar with the system, it may help to start by using the master four digits to locate the map square, then work out which quarter of the square the reference falls into, remembering that a third digit of ‘5’ indicates half way along a side of the square.
