The Charles Close Society for the study of Ordnance Survey maps

Digital Images Archive

GSGS 3775 1:20,000 Grantown-on-Spey

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67. The standard 1:20,000 military map of Great Britain was GSGS 2748, begun in 1918, and was constructed on Cassiniís Projection on the origin of Dunnose. Nearly one hundred series sheets were in print by 1930 when the decision was taken to alter the scale from 1:20,000 to 1:25,000, the grid from the British system to the Modified British system, A new GSGS number was allocated, 3906. The true origin of the grid was the same as the map, at Dunnose on the Isle of Wight. GSGS 3775 'Grantown-on-Spey' was a special 1:20,000 mapped in the style of the GSGS 2748 regular edition. The principal point of distinction between this and the national map is the use of a local grid, overprinted in purple at 1000 yard intervals, parallel and perpendicular to the sheet lines. The reason for the use of this local grid is at present unknown; the map may have been made for a local military exercise in 1925.

From a copy in a private collection