Land Tasmania GDA2020 Implementation
This page provides information about Land Tasmania's implementation of GDA2020 including the overarching policy and individual policy statements. The policy was first released in March 2020 in support of the ANZLIC goal that by 30 June 2020 "all member agencies in Australian states and territories will be ready to deliver and recieve foundation spatial data on the GDA2020 datum".
Land Tasmania has subsequently revised the policy to reflect changes to the intended delivery dates of some of the implementation impacted by the consequences of COVID19, and to incorporate the latest information on the relationship with the WGS84 ensemble used in web mapping.
GDA2020 Implementation Policy
The policy describes how Land Tasmania intends to address the management of GDA94, GDA2020 and WGS84 ensemble as it implements the first stage of Australia's datum modernisation program. It aims to facilitate the adoption of GDA2020 by all Tasmanian geospatial users and suppliers by ensuring that Land Tasmania's timelines for implementation and support are clear.
The policy concludes with 13 statements on individual aspects of the implementation which have been reproduced below and expanded with additional information where appropriate.
The policy document, along with the results of a GDA2020 readiness questionnaire conducted in 2019, should be consulted for background information underpinning these statements.
Land Tasmania GDA2020 Policy (336Kb)
Summary Report - Results GDA2020 Readiness Questionnaire (996Kb)
1. Land Tasmania will continue to provide Positioning (survey control mark) data in both GDA94 and GDA2020 for the forseeable future
- The Survey Control Marks Database (SurCom) is the on-line point of truth for coordinates of permanent survey marks on various datums used in Tasmania.
- The LIST Survey Control dataset is generated daily (refreshed overnight) from SurCom.
- Currently SurCom defaults to GDA94 as the horizontal datum reported on a survey control mark and other horizontal datums, including GDA2020, must be chosen from a drop down list.
- The LISTmap Survey Control Layer currently only provides coordinates and station summaries on GDA94 datum.
- Additional information about the physical realisations of Tasmanian geodetic datums is availabe here.
2. There are no CORS services in Tasmania provided by DPIPWE. However, all CORS services providers operating within Tasmania comply with the national policy concerning the provision of GDA94 and GDA2020 coordination products
- Nationally, CORS service providers have agreed to deliver GDA94 and GDA2020 corrections for the forseeable future.
- The three providers operating in Tasmania have released details on how to access the real time correction stream in either datum :
- AllDayRTK GDA2020 update to subscibers can be found here - users specify the server address related to the mountpoint for GDA94 or GDA2020
- SmartNET update to subscribers can be found here - users select the required mountpoint from the NTRIP source table on their instrument
- VRS Now issued a support bulletin to subscribers by email - users select the required mountpoint from the same server address and port
3. Land Tasmania will continue to hold and maintain Foundation Spatial Data and maintenance environments in GDA94, except for Positioning (survey control) data which is maintained in GDA2020.
4. From 30th September 2020, Land Tasmania Foundation Spatial Data will be available for delivery in GDA2020 upon request. This includes vector and raster datasets but does not include web services.
5. From 30th September 2020, Land Tasmania will be able to receive stakeholder data in both GDA94 and GDA2020.
6. Where transformation of Tasmanian spatial data is required between GDA94 and GDA2020, the 7-parameter transformation method will be the default transformation method used by Land Tasmania. The Conformal and Distortion NTv2 grid transformation method will only be applied if a specific assessment concludes this is appropriate. In all cases, the transformation method will be included in the metadata record for the transformed dataset.
7. Any spatial dataset provided to Land Tasmania must have an associated Metadata Statement detailing what projection, datum, epoch (where appropriate) and transformation (where appropriate) has been used.
8. All LIST web services (services.thelist.tas.gov.au) and all web mapping applications (LISTmap, COP, LISTdata) will remain publishing data on WGS84. Data shall be transformed via a null transformation from GDA94 to WGS84 until such time that an alternative agreed technical solution is recommended by ICSM.
9. All new TASMAP hardcopy and digital products will include a change to the Horizontal Datum field, changing from 'Geocentric Datum of Australia 1994' to 'Geocentric Datum of Australia 2020'. This change was applied from 1 March 2020.
10. Survey Directions, Tasmania : All surveys of land for a statutory purpose in Tasmania that are commenced after 30th September 2020 will need to be coordinated on GDA2020, or otherwise at a date specified by the Surveyor-General.
- The aim is to keep the date of adoption of GDA2020 in the Directions as aligned as close as possible to the other Land Tasmania implementation dates. However, final adoption date may vary slightly due to legal requirements in the process to change the Survey Directions.
11. From 30th September 2020 all adminstrative plans lodged in the Central Plan Register dated post 30th September 2020 shall be based upon the GDA2020 datum, except where use of another datum is prescribed by a legal instrument.
- The date for operational implementation of GDA2020 was chosen to retain alignment with other GDA2020 implementation dates.
- Refer to GDA2020 Impacts on Legal Framework for further information
12. Australian Height Datum (Tasmania) - AHD83 - will continue as the legislated height datum for mainland Tasmania except where an alternative height datum is required, for example when undertaking hydrographic surveys or special projects.
- AHD83 only applies on mainland Tasmania and near onshore islands e.g. Bruny Island.
- Vertical datums on King and Flinders Island are completely unrelated to AHD83.
- GNSS does not directly measure heights above any of these datums as GNSS heights are referenced to a mathematical ellipsoid surface, not a physical (gravity based) surface.
- Different Ausgeoid models are required to be applied to GDA94 and GDA2020 ellipsodial heights to deduce AHD83 heights.
- The new Australian Vertical Working Surface (AVWS) has been developed for use cases where a highly accurate gravity based reference surface is required. It is expected its use will increase over time but this will be driven by demand and it will co-exist with AHD83.
13. Land Tasmania will not be able to formally accept ATRF2014 data but will nominate at a future date when it will be able to accept this information.
- It is envisaged that GDA2020 will be the national datum of choice for most use cases for the forseeable future.
- ATRF2014 is expected to be used in areas such as Intelligent Transport Services and the scientific community.