
4 0 c m
34cm
actual image size: 26cm x 32cm
Description
This theodolite was made by Troughton and Simms and first used in 1828 for checking the Lough Foyle base, Northern Ireland. The theodolite was used for measuring both vertical and horizontal angles. This instrument was used for many years in conjuction with the Ramsden three foot geodetic theodolite in the preparation of the Primary Triangulation of Britain, the network of reference points underpinning Ordnance Survey maps.
Image Details
Image Ref.
10280200
© Science Museum / Science & Society Picture Library