Historic Sydney Observatory Trig Point - Sydney, NSW
Posted by: 
BruceS
S 33° 51.584 E 151° 12.270
56H E 333907 N 6251946
Original Sydney Observatory trig point later superseded by trig point on top of the Observatory.
Waymark Code: WMFV97
Location: New South Wales, Australia
Date Posted: 12/02/2012
Views: 24
From information sign:
Stone pyramid for surveying Sydney
This historic stone pyramid is survey marker or trig station, erected about 1880. Its accurate position measured by the Observatory's transit circle telescope, was used in survey Sydney.
Surveyors would climb to the top of the marker and measure angles to visible landmarks. With these angles they could used triangulation or trigonometry to draw up maps of property boundaries and sewage lines.
As the area around the Observatory became built up, a new survey maker was placed high on top of the time ball tower. Trig E, as it was known, was used by surveyors until the early 1980s, when the marker was removed for safekeeping.
Recently the survey marker on top of the tower was replaced and position was re-established with the latest GPS techniques by the NSW Department of Lands. Now known as Observatory E. its coordinates are: latitude 33° 50' 55" S, longitude 151° 12' 4" E.