The NSW Integrated The NSW Integrated Survey GridSurvey Grid

ISG66 (1972-1994)ISG66 (1972-1994)

School of Surveying & Spatial Information Systems, University of New South Wales, Sydney. May 2010, D.Logan

Discussion Discussion OverviewOverview

• History of NSW Survey and evolution.

• Advantages of an ISG.

• Specifications of the ISG.

• The demise of the ISG.

History of Survey Applications History of Survey Applications in NSW 1830-1966in NSW 1830-1966

• 1830’s first trig stations in NSW.• First NSW Datum created and based on Lake George/Parramatta

Observatory (Lat/Long). • Sydney City Council: Creates a networked survey (NDS circa 1880)• NSW needed an integrated surveying system, but why did it take

130 years to create one?• 1949: The Survey Co-ordination Act NSW was commissioned. All

surveys must be connected via the network of Trig Stations. But the Act wasn’t enforced.

• Post WWII Royal Australian Survey Corps completed surveys for an Australian Geodetic Network. This formed the basis of the AGD66 datum.

• 1965: AMG projection was adopted as a national standard for topographic surveys. NSW Land Titles needed a better projection for property surveys.

History of Survey Applications History of Survey Applications in NSW 1968-1994in NSW 1968-1994

• 1968: First discussions of an integrated survey system (ISS). This was conducted by the Institute of Surveyors NSW.

• Chief surveyors from 12 government departments as well as academics from UNSW and USYD were involved to investigate an ISS.

• 1970: the Minister for Lands approved the ISG program and instructed the Surveyor General to commence the Sydney Pilot Survey.

• 1971: Pilot Survey established 66 controls in Sydney CBD, and cross checked by 18 survey parties.

• 1972: Draft legislation drawn up and provided to the Institute of Surveyors.

• 1974: Plan for ISG controls marks (SSMs) to be established throughout all NSW urban areas, timeframe… 5 yrs

• The ISG was now used as the NSW standard for cadastral mapping until GPS datums were standardised.

Advantages of the ISGAdvantages of the ISG

• One correlated system for all NSW surveys.• Sets a basic control for a cadastral framework.• Creates a legally definably property boundary

that can be used for the Torrens Title System of Subdivisions (DPs).

• Minimises scale factor corrections for area surveys (conformal projection).

• Projection corrections for a 2°zone are less than 1:8000 there these could be omitted.

Specifications of the ISGSpecifications of the ISG

• A variant of the UTM, using Redfearn’s (1948) Formula, but altering for NSW:

1. Projection parameters determined from state Trig network.2. Central Meridian (being the center of each zone).3. Central scale factor (0.99994).4. False Northing and False Easting, (300,000 and 5,000,000).5. Longitude of origin being the equator.6. Units: Meter.

• Comprises 2° zones that are directly related to the 6° AMG, these are then subdivided further. Yielding ISG zones:

• 54/2, 54/3, 55/1, 55/2, 55/3, 56/1, 56/2, 56/3, with a 1/4° overlap.

• Uses the AGD66 Datum thus ANS ellipsoid.

The Demise of the The Demise of the ISGISG

• AGD66 was superseded by AGD84, NSW declined to move.

• Due to the fact that a geocentric datum was in the works. QLD, SA, NT, WA moved to AGD84 regardless.

• Development of GPS proved far more accurate than trigonometric surveys.

• As of 2005 the only government authority still using ISG is the Australian Rail Track Corporation.

ReferencesReferences

• Featherstone, W.E., Galloway, D., Goulding, P.and Reit, B.G. (1999) ‘Transformation between Australian datums using a modified transverse Mercator projection’ Cartography, vol. 28, no. 1, pp. 19-32.

• Fletcher, L.N. (1976) Manual of the New South Wales Integrated Survey Grid, New South Wales Department of Lands, Sydney

• Land and Property Management Authority (2010) Surveying Issues, Land and Property Management Authority, viewed May 2010. <www.lands.nsw.gov.au/survey_and_maps/geodesy/gda/surveying>

• Williamson, I.P. (1984) ‘Coordination of cadastral surveys in New South Wales’, The Australian Surveyor, vol. 32, no 324, pp. 274-292.