William Bailey was a captain in the Royal Engineers who was sent out to the Cape Colony in 1859 with a sergeant and about a dozen men from the Ordnance Survey to conduct a trigonometrical survey along the southern Cape coast. The main purpose of the survey, which was funded by the government of the Cape Colony, was to provide the Hydrographic Department of the British Admiralty with easily observable coastal beacons to be used by hydrographic ships to establish their exact positions. Thus the survey would form the basis for more accurate coastal charts. The need for better charts was evident from the large number of shipwrecks along the southern Cape coast at the time, including that of the troopship Birkenhead in 1852 with the loss of over 450 lives. The survey would also extend the geodetic chain surveyed by Thomas Maclear* eastwards for some 800 km and would form the basis for later secondary triangulation of the coastal districts.
Bailey arrived in Cape Town on 16 March 1859 and started the survey late in April. One party of men selected observing stations and marked them by a small hole cut in rock. Two other parties made the necessary theodolite observations, the observers being Bailey and Lance-Corporals Purdy, McConomy and McDonald. At its western extremity Bailey incorporated two sides of Maclear's triangles, namely Kapokberg to Great Winterhoek, and Zonder Einde to Potteberg. From these he measured a double chain of triangles eastwards to the Kei River, which was then beyond the colony's eastern border. The chains extended inland some 80 to 200 km. Smaller triangles linked them to beacons near the coast. The fieldwork proved difficult, being hampered by veld fires, the uneven coastal terrain, and transport problems, and was completed in 1862. A baseline of just under 9 km was measured between the Great Fish River and the Kap River, near their junction (some 45 km east of Grahamstown). Its measured length corresponded very closely with its length as calculated from the results of Maclear's survey. Astronomical determinations of latitude and azimuth were made at the eastern end of the baseline. The survey party embarked on the coastal steamer Waldensian at Algoa bay in October 1862 to return to Cape Town, and from there to England, but tragedy struck when the ship was wrecked at Struys Point, with the loss of all the field-books and sketches. Using interim reports and copies of observations supplied to others Bailey was none the less able to compile his Report on the trigonometrical survey of a portion of the Colony and British Kaffraria for the Cape government in 1863. A report was also published the next year as "Triangulation of part of the Cape Colony and British Kaffraria, 1859-1862", in Royal Engineers, Professional Papers (new series, No. 13, pp. 46-66). Both reports included an assessment by T. Maclear and Surveyor-General Charles Bell* of the value of the survey.
The loss of Bailey's documents made it difficult to assess the accuracy of the survey. Most of the work appears to have been carried out with sound judgement and meticulous attention, though this does not apply to some parts of it, particularly in the eastern portion of the survey in which a number of errors were later found. The results were quite acceptable to be used in the compilation of a new 1:800 000 scale map of South Africa by the Surveyor-General's office in 1896. The latitude and longitude he determined for Fort Selwyn at Grahamstown was also still accepted as accurate in 1882 when L.A. Eddie* observed the transit of Venus there. However, the errors, and particularly the impossibility of checking them in the original field-books, were serious enough to ensure that the results were not incorporated in the geodetic survey of the Cape Colony and Natal during the eighteen-eighties. Bailey's stations were well chosen however, and many of them were re-observed as part of the geodetic survey. Dr David Gill* later compiled a "Report on a rediscussion of Bailey's and Fourcade's surveys and their reduction to the system of the geodetic survey", which was published as Volume 2 of his Report on the Geodetic Survey of South Africa... (Cape Town, 1901).