Geodetic Survey Baseline,
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There are three elements to the Geodatic Survey Baseline: South Base (north side of Princes Highway, Hoppers Crossing; North Base (South of Sayers Road) and Green Hill Extension (off St Marys Road, Eynesbury – Crown Allotment B, Section XXV, Parish of Werribee).
The South Base and North Base markers both consist of a solid bluestone set into the ground, capped by a heavy stone. A plug of gun metal with a platinum centre is set into the stone base. The capping stone at South Base has been broken. North Base was last inspected by the Office of the Surveyor General in 1989, soon after it was gazetted as an ‘area of historic interest’ on 23 August 1988. The marker was covered by piled stones covering the stone cap and marked by four marker posts.
The Green Hill extension geodetic survey point consists of a platinum centre in a gun metal plug. Unlike the other two points it did not retain a bluestone cap when last inspected by the Office of the Surveyor General. Nearby is the Eynesbury Beacon, an Army Trig beacon constructed of tubular steel. Green Hill is also important geologically, as one of the major topographic features of the Werribee plains and for the evidence of the Tertiary sediments underlying the Werribee plains that can be seen within it erupted volcanic materials.
Development has now obscured direct line of sight between the three markers.
Three permanent markers are associated with the establishment of the Victorian Geodetic Baseline Werribee in 1860 by Robert Ellery, Government Astronomer and Supervisor of the Geodetic Survey of Victoria: South Base, North Base and Green Hill extension.
Located on the east side of the Werribee River, north of the railway, the baseline was five miles in length. It was extended northwards to a total of nine miles to Green Hill by triangulation. The baseline was measured using three ten-foot iron rods made in Victorian against the New South Wales standard originally obtained from the Ordnance Survey Department of South Hampton in England.
The north and south ends of the five mile baseline ‘were permanently marked with sunken masonry piers, having in their upper surfaces a piece of brass carrying a platinum dot indicating the termini of the measure. These marks were then covered with heavy cap stones’. The third mark, at the end of the extension to the north, on Green Hill, ‘consists of a sunken bluestone block with a projecting iron spike’.
The South and North Bases, and the location of the third mark on Green Hill are shown on a 1915 Army Ordnance map of the area. Examining this map it is possible to follow the course of the baseline from the present day location of Hoppers Crossing, across the Tarneit Road to the North Base south of Sayers Road and close to the Werribee River, and then across the Werribee River to Green Hill with Staughton’s Eynesbury Estate.
The South Base is possibly the best known of the three permanent markers because of its location close to the Princes Highway and the various campaigns to ensure its preservation. A photograph of the South Baseline stone appeared in ‘Trust News’, after the National Trust has classified the three historic markers as ‘physical evidence of an important element of the 19th century Geodetic Survey and consequently the earliest maps of Victoria’.
Robert Lewis John Ellery was a physician as well as an astronomer. He was of the founders of the Royal Society of Victoria, and was the foundation President of the Institute of Surveyors.
Werribee,” Wyndham History, accessed June 29, 2022, https://wyndhamhistory.net.au/items/show/1045.