#Old theodolite verification

At its heart GNSS uses trilateration, the cousin of triangulation, employing the observation of distances rather than angles to determine position. However, itвЂ™s nice to note that fundamental positioning principles are never far away. The gulf between the trusty theodolite and the modern OS NET and Global Navigation Satellite System (GNSS) technology we use now is almost unimaginable. Despite this, the original model of instrument was still preferred not only to ensure the highest consistency of measurement, but the older, heavier instrument was more stable in the windy Highlands of Scotland! How we survey Britain today The book also notes that a further 10 theodolites were purchased in 1946-47 that were of a lighter and more compact design. The other instrument is displayed in the Record Room of the Ordnance Survey at ChessingtonвЂ™. One instrument was destroyed when the Ordnance Survey office at Southampton was bombed in 1940, and one was damaged rather less gloriously by being dropped from a steel tower in 1951. Attempts were made to recover them in 1944, but without success. Of the reminder, 3 were buried near Dunkirk before the 19 thВ Field Survey Company, R.E. It is of interest that 6 are still in use, and have been used for such operations as the transfer of geodetic levels by trigonometrical methods, where the larger vertical circle of this early type of instrument is of great advantage. вЂAs far as can now be established, 12 of these instruments were used between 19. Pride of place in the OS reception of our HQ in Southampton. The date was 21 June 1791, which we recognise as the birth of Ordnance Survey. Transforming his foresight into reality, the Board of Ordnance bought a second new (and improved) Ramsden theodolite.

Praised by newspapers as an вЂincomparable engineerвЂ™, Roy was awarded the Copley Medal вЂ“ the Royal SocietyвЂ™s highest accolade. Years later, this five-mile line formed the basis of the Principal Triangulation of Great Britain.

#Old theodolite verification

Utilising the theodolite and trigonometry, Roy created a network of accurately measured triangles that extended to France and then back to a verification baseline in Kent. A dense framework of triangles with accurate coordinates at the nodes allows for accurate surveying of map features. By using angle measurements and at least a single measured baseline length, a whole country can be measured using the triangulation method. Under the authority of the Master General of the Board of Ordnance, Roy began the London/Paris triangulation in 1785. Three years in the making and measuring three feet across, he produced the spectacular Great Theodolite! Nobody but Jesse Ramsden, the leading instrument maker of the day, could make this exceptional apparatus.

To undergo this project, he needed a more sophisticated theodolite than had previously existed.ДЄs you can imagine, creating something like that would take a very specific skillset. Made to the same pattern as the Great Theodolite, OS bought this Ramsden theodolite in 1795 and it now resides at our HQ in Southampton.ДЄlthough technology was limited, Roy was convinced вЂthe honour of the nationвЂ™ depended on creating a superior map of Britain unparalleled in its accuracy.