British Army Navigational Dividers

As was discussed here, dividers are used in navigation to plot distances on a map. The legs of a pair of dividers is set to the scale of the map and by walking them across from ‘point a’ to ‘point b’ it is possible to get a good estimate of distance. The example previously covered was a pre-WW2 RAF example. Tonight we are looking at a second version, this time of wartime production:imageThe design of this pair of dividers is a little simpler, but like the earlier design a large circular spring at the apex tensions the two arms of the instrument:imageA thumb wheel and screw allows precise adjustments of the legs to match the scale of the map:imageThis example is stamped with a /|\ mark and a date of 1943:imageDividers were used as much for navigation on land as they were in the air, especially in the desert where the terrain was so featureless that steering a course was much like navigating at sea. The manual for operations in the desert explains how the dividers were used:

For desert navigation you require: (i) a map; (ii) a pencil; (iii) a ruler; (iv) an India rubber; (v) dividers or compasses; (vi) a protractor; (vii) an odometer; (viii) a prismatic compass; (ix) a means of transport; (x) a navigation ledger or log book. The log book has a number of columns, each devoted to: the starting map reference, the starting odometer reading, the date, the time, the distance to travel, the compass bearing, the final odometer reading, and the final map reference.

On the log book, you indicate the date and time, and the initial odometer reading. You mark the destination with a dot on the map. You then connect from you present position with a pencil line. You measure the exact distance with the dividers. With the protractor, you find the compass bearing you have to travel, and the distance to be travelled. You then proceed on the compass bearing until you reach the place calculated to be the final odometer reading. You are now at your new destination.

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