two digits of the year. However, the rock mark was lost at the turn of the century, probably due to quarrying. Although two separate surveys were carried out, in many instances both surveyors used the same tree to mark the corners. As a result of the two different surveys, Rowland and Roberts defined the border in different positions. At the direction of the Queensland Surveyor-General, Roberts deviated from the definable position of the watershed in order to increase accuracy of the survey. The New South Wales and Queensland governments have since essentially adopted the survey of Roberts in preference to that by Rowland. In 2001 as part of the celebration of the centenary of the Federation of Australia, a monument to Roberts and Rowland was placed on the border of Queensland and New South Wales at . Gregory's and Greaves' survey The initial survey of latitude 29ºS was fixed in 1865 by the Queensland Surveyor General, Sir Augustus Charles Gregory and District Surveyor from Armidale, New South Wales, William Albert Baylesford Greaves. The purpose of the survey was to give landholders in the vicinity of the border an indication of the extent of their leases and rent payable in each colony. WD Campbell reported in The Surveyor in 1895:"In 1865, an arrangement was made between New South Wales and Queensland for the fixing of the position of the intercolonial boundary line, the 29th parallel of latitude, at the intersections of the Rivers Barwon, Mooni, Bokhara, Narran, Biri and Culgoa, to enable the Governments of the respective colonies to adjust the rents of leases of the several pastoral runs affected, some of which were partly in both colonies... The marking of the border was done with steel [iron] pins one inch in diameter and two feet long, driven a few inches below the surface ... This process was repeated at each of the above named rivers, and the work was completed in five or six weeks." The official determination survey The official survey of the 29ºS parallel was conducted by John Brewer Cameron (NSW) and George Chale Watson (Qld) between 1879 and 1881. Astronomical observations were taken at the Barringun telegraph station to determine the latitude and longitude. Following these observations, the Zero Obelisk was erected on the banks of the Warrego River, just north of the town. From this mark, the first 5 mile chord was produced westerly and the