Located to the south of Lake George, as its name suggests, the Lake George South Base Trig was the last of three trig stations that acted as a reference point or baseline from which all surveys in NSW originate (the other two being TS776 Lake George North Base and possibly TS5225 St George). The baseline was completed in 1874, after the Government Astronomer, Mr Smalley, reported that Lake George had been unanimously chosen as a site for the first baseline in 1869. The time taken to establish the trig station was largely due to “the greatest flood ever known”, which caused Lake George to fill and inundate the initial sites that had been selected.
The Lake George South Base Trig is an unusual trig design, with a mushroom-like shape on a large cairn constructed of small rocks.
The historic Lake George South Base trig station has one of the highest “TrigStar” scores, which is based on an assessment of trig stations against 12 criteria that is used to calculate a score out of 100 and a corresponding rating out of 5 stars. The top 500-700 trig stations (which have a rating of 4 or 5 stars are represent about the top 10% of passive trig stations) are generally maintained by the NSW Department of Land and Property Information.
It is worth noting that TS778 Lake George South Base (recall where the Trigonometrical Survey of New South Wales started all those years ago in 1867) is currently the highest-scoring trig station in NSW, closely followed by TS5816 Tarella and TS5566 Sutton Forest.Preservation and Upgrade of Trigonometrical Stations in NSW
Getting to the Lake George South Base Trig
It’s relatively easy to reach the trig – but it is located on private property and prior permission should be sought. The trig is next to an unsealed private access road, which is off Bungendore Road in Bungendore. It’s about 39km (35min) from Canberra and 16km (15min) from the Federal Highway.
- Australian Town and Country Journal, Sat 21 Mar 1874 – The Base Line at Lake George
- Preservation and Upgrade of Trigonometrical Stations in NSW [PDF]
- J.B. McLean – A Short History of the Trigonometric Survey of NSW (1967) [PDF]