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
The Surveyor-General’s Land Boundaries Section has delivered the MGA2020 coordinates for survey marks in the Survey Mark Database (SDB) replacing the MGA94 coordinates.
Survey Mark details ordered from Property Location Browser (PLB) and SAILIS now report MGA2020 coordinates of permanent survey marks (PSMs). PLB should be used as the primary search tool for PSMs mark details as the report contains additional fields to the SAILIS survey mark report.
The following short videos demonstrate how to:
- Search and report the details of survey marks from PLB
- Export the details of survey marks from PLB as a CSV file.
For alternative versions of these instructions contact DPTI.SurveyOperations@sa.gov.au
MGA94 coordinates of survey marks are no longer available from PLB or SAILIS. A static version of the MGA94 SDB last updated 1 December 2018 is available for download as an excel spreadsheet under the header ‘Survey mark coordinate database’ at www.sa.gov.au/cadastral-surveying. The Historical GDA94 version is also available for download as a zip file containing a shapefile and associated projection files from the South Australian Data Directory, “Data.SA”.
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 coordinates
Coordinates of survey marks that are not provided as a requirement of certified survey plans can be be provided to the Survey Operations Unit on a voluntary basis. See the Voluntary data & coordinate provision for survey marks (404.4 KB PDF) guide 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.