The Principal Triangulation of the United Kingdom ¹

Abstract

THIS publication of the Ordnance Survey deals with a subject of especial interest, since it sets forth the operations which were undertaken in 1910, 1911, and 1912, in order to test the accuracy of a portion of the principal triangulation of the United Kingdom, and discusses the results obtained. This triangulation, which was observed during the seventy-two years, 1783–1851;, comprises 552 triangles, and the mean error of an angle as given by Ferrero's formula, M=√σδ²/3n is +1.8ⁿ, a value which is somewhat larger than that of recent first order triangulation. This raised the question whether the triangulation was suitable for incorporation with recent Continental geodetic work. It was therefore decided to measure a new base in a part remote from the principal bases of the triangulation at Lough Foyle and on Salisbury Plain, and to re-observe a portion of the principal triangulation in its neighbourhood.