ABSTRACT
The union between England and Wales was begun in 1284 and formalized in 1536. England and Scotland agreed to join as Great Britain in 1707 and with Ireland in 1801. As Britain entered the First World War, surveyors, draughtsmen and printers from Ordnance Survey were posted overseas. Working in appalling conditions alongside the troops, surveyors plotted the lines of trenches, and for the first time, aerial photography was used to capture survey information. The Davidson Committee’s final report set Ordnance Survey on course for the 21st century. The National Grid reference system was introduced, using the metre as its measurement. The original triangulation of Britain was carried out between 1783 and 1853 and is known as the "Principal Triangulation." The counties of the United Kingdom were based on local Cassini-Soldner projections that had the typical scale factor equal to unity, no false origin, and a single triangulation station as the projection origin.
