Land Tasmania GDA2020 Implementation

FThis 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 receive 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 COVID-19, 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)

Implementation Statements

1. Land Tasmania will continue to provide Positioning (survey control mark) data in both GDA94 and GDA2020 for the foreseeable 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.
SurCom was updated to default to GDA2020 as the horizontal datum reported on a survey control mark on 14 October 2020. GDA94 and other horizontal datums must be chosen from a drop down list.
The LISTmap Survey Control Layer has provided GDA2020 and GDA94 coordinates and station summaries from the "Identify Results" window since1 September 2020.
The csv download file available from the Survey Control Marks Database webpage has since 1 September 2020 contained an extract of basic coordinate information for all control marks in Tasmania with GDA94 and GDA2020 horizontal coordinates
Additional information about the physical realisations of Tasmanian geodetic datums is available here.

LISTmap Survey Control Identify Results window since 1 September 2020

2. There are no CORS services in Tasmania provided by NRE Tas. 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 provide details on how to access the real time correction stream in either datum :

AllDayRTK users need to contact AllDayRTK directly for instrucitons on how to access the required correction stream
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.

See Land Tasmania Services and Data Applications Summary for more details

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.

See Land Tasmania Services and Data Applications Summary for more details on Foundation Spatial Data
Web services are restricted to using the WGS84 ensemble for interoperability between all web services, see Implementation Statement 8 below.

5. From 30th September 2020, Land Tasmania will be able to receive stakeholder data in both GDA94 and GDA2020.

See Land Tasmania Services and Data Applications Summary for more details and note also statements 6. and 7. below

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.

See Choosing a GDA94 - GDA2020 Transformation and Preparing Metadata to Accompany Spatial Datasets for further discussion.

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.

See Preparing Metadata to Accompany Spatial Datasets for further information about metadata.

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.

Web services are restricted to using the WGS84 ensemble for interoperability between all web services
Refer to Web Mapping and WGS84 / Web Mercator for further details.

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.

Refers to the date the field survey is commenced as required under 3.3.2.1 (i) of the Survey Directions, Tasmania

11. From 30th September 2020 all administrative 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 ellipsoidal 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 foreseeable future.
ATRF2014 is expected to be used in areas such as Intelligent Transport Services and the scientific community.