Intergovernmental committee on surveying and mapping
The Intergovernmental Committee on Surveying and Mapping (ICSM) are the national governing authority on geodesy.
Changes are being made to the system that underlies Australia’s location information. The changes will bring Australia’s national latitude and longitude coordinates into line with global satellite positioning systems, enabling smartphones and other positioning technologies to accurately locate features marked on our maps.
The changes are needed because national and global location information systems operate differently, and they are diverging. Australia’s national grid of latitude and longitude coordinates moves with the drift of the continent, like a giant net tied to known reference points on the landscape. Together, these reference points and latitude and longitude coordinates are known as a geodetic datum.
Australia is in the process of changing to a new official geodetic datum called the Geocentric Datum of Australia 2020 (GDA2020), which is replacing the Geocentric Datum of Australia 1994 (GDA94). GDA94 was preceded by Australia’s first official national datum called the Australian Geodetic Datum. It had two versions – Australian Geodetic Datum 1966 (AGD66) and Australian Geodetic Datum 1984 (AGD84).
The changeover is implemented individually within each jurisdiction with national coordination facilitated by ICSM. The GDA Modernisation Implementation Working Group within ICSM was formed to manage that coordination. For more information about the change, see ‘What is GDA Modernisation?’
Also see the Standard for the Australian Survey Control Network (SP1), Version 2.1, October 2014
Geoscience Australia is the national focal point for coordination of geodetic information and data, and maintains a national network of geomagnetic observatories which forms part of a global observatory network.
More information on datum modernisation and geodesy.
Free online GPS processing service.
The Satellite based Augmentation System (SBAS) is a recent initiative to develop a world leading satellite positioning capability for Australia which links to the National Positioning Infrastructure (NPI).
The Survey Operation’s geodetic team are responsible for supporting South Australia’s geodetic framework relating to:
- SA input to the National Positioning Infrastructure
- Refine and maintain SA GDA 2020 Dataset
- Communicate the GDA2020 datum shift to the user community
- Provide and maintain a geodetic ground station network
- Cadastral integrity protection through maintenance of the “Tertiary Network”
- Provide the datum to underpin the foundation spatial data sets
- Maintenance of an AHD height network
Permanent survey mark coordinates
From February 2019, the Survey Mark Database (SDB) maintained by the Surveyor-General’s Survey Operations Unit has been delivering MGA2020 coordinates for survey marks.
Survey Mark details ordered from the South Australian Property and Planning Atlas (SAPPA) and SAILIS report MGA2020 coordinates and other details of permanent survey marks (PSMs). SAPPA should be used as the primary search tool for PSMs mark details as the report contains additional fields to the SAILIS survey mark report.
MGA94 coordinates of survey marks are no longer available from SAPPA or SAILIS.
Download a static version of the SDB MGA94 PSM coordinates (XLSX, 29855 KB) last updated 1 December 2018
The positional uncertainty (PU) of MGA2020 coordinates is now reported with the survey mark details. PU of coordinates is calculated from the National network adjustment to provide an indication of the accuracy of the coordinates compared to the reference datum (GDA2020). Some PSM coordinates will have a null PU assigned to them as their coordinates are classified as order 9 and are not in the National adjustment. New orders have been assigned to survey marks to align with their coordinate’s PU, however the PU is the primary indicator of the accuracy of the coordinates.
PSMs in known reactive soil areas will be assigned a Type B PU attribute that may increase their PU. Type B is an international standard relating to measurement uncertainty based on environmental factors.
Voluntary provision of permanent survey mark data and coordinates
Coordinates of survey marks that are not provided as a requirement of certified survey plans can be provided to the Survey Operations Unit on a voluntary basis. This information may assist with spatial cadastre improvements and national network adjustments. See the Voluntary provision of survey mark data & coordinate guide (PDF, 408 KB) for recommendations for this data.
An example of the input values required can be found on the second sheet of the workbook at the bottom of the spreadsheet.
Australian Vertical Working Surface (AVWS)
The Australian Vertical Working Surface (AVWS) is a new reference surface for heights in Australia based on the Earth’s gravity field.
As part of an ongoing improvement process, the Government of South Australia is partnering with Geoscience Australia (GA) to undertake an airborne gravity survey over Adelaide and surrounding regional areas from late 2020.
This survey will collect new gravity data which will provide height information at a greater accuracy.
Height information is used when producing elevation models crucial for construction and development activities, as well as environmental risk analysis (i.e. flooding, sea level rises and bushfire risk).
Find more information here (PDF, 238 KB), or visit the Intergovernmental Committee on Surveying and Mapping website for more information about the Australian Vertical Working Surface.
In the meantime, if you have any questions, or would like to register for updates, please contact us at DIT.GravityAVWS@sa.gov.au.