Charles Todd draws on astronomy to fix true 141st meridian border of South Australia-NSW – not conceded by Victoria
Two years before he ventured into the outback to oversee the Darwin-Adelaide overland telegraph line project, Charles Todd was ion a field trip exercise that used astonomy to calculate the correct position, aligning with the 141st meridian, of the South Australia border with New South Wales and Victoria. Victoria refused to conceds the 3.6 kilometres of territory to the west that deviated from the offcially patented border.
Images courtesy State Library of South Australia and OpenStreetmap via Wikipedia
Charles Todd, although not trained in that speciality, added surveying to his accomplishments as the South Australian government’s astronomical and meteorological observer, head of the electric telegraph department and postmaster general in the later half of the 19th Century.
As astronomical observer, Todd was responsible for accurately setting South Australia’s position and its time. He calculated the precise position of his Adelaide Observatory on West Terrace, Adelaide city, by using astronomy observations, enabling a standard point for geodetic surveys to to be set.
In May 1868, Todd applied his astronomy skills on a field survey near Chowilla on the River Murray to determine the position of 141st longitude meridian – the officially patented position from 1839 of the border between South Australia and New South Wales. The survey was a response to a growing suspicion that the border between South Australia and Victoria (supposed to coincide with the 141st meridian) had been marked in the wrong position.
Todd worked with the government astronomers of New South Wales (George Smalley) and Victoria (Robert Ellery), using the transit of 11 selected stars and information linked by telegraph wires, to calculate the exact position of the 141st meridian. They proved that the marked border between South Australia and New South Wales/Victoria was too far west by at least 3.6 kilometres (2.25 miles).
Todd issued an excellent report on the exercise, explaining the techniques used, the simple mathematics and the empirical checks for accuracy in clear and basic words. New South Wales made the adjustment to its border but Victoria – despite Melbourne Observatory being involved in calculatig the true 141st median position – refused to concede the territory to South Australia, setting off a long dispute that remained unresolved.
South Australia’s other great 19th Century government technocrat, surveyor general George Goyder, had trained the many surveyors used by Todd for his major feat: overseeing the Adelaide-Darwin overland telegraph line project, completed in 1872. In 1882, Todd was elected as inaugural president of the South Australian Institute of Surveyors, a position he retained until 1888. One of the institute’s first actions was to seek setting up a board of examiners to recommend the issue of surveyors’ licences to cover legal surveys.
With the joint support of Todd and Goyder, South Australia’s Licensed Surveyors Act was proclaimed in 1886. Candidates for survey licences were examined in mathematics, survey instruments, drawing, the field practice of land surveying, and astronomy. Todd continued to set and mark the astronomy exam papers until he retired in 1905.
