Australia's measurement system provides for a hierarchy of measurement standards by which traceabilty of a measurment unit can related back to the legal unit, including the ability to specify "conversion" factors between a legal unit of measurement and other measurements of the same type. In particular, it allows for a measurement called a "Recognized value Standard of Measurement" to provide certainty for the measurment type and for which there is no prescriptive requirement to use as the only unit of that measure.
Legal Definition of GDA2020
GDA2020 is defined in the National Measurement (Recognized-Value Standard of Measurement of Position) Determination 2017 by the coordinates on 109 GNSS Continuously Operating Reference Stations. ICSM's member government agencies have specified GDA2020 coordinates on survey control across the country and published how to transform coordinates between GDA2020 and other Australian datums and international Reference Frames.
Accordingly there is a legally traceable link between a location specified by a coordinate on other national datums such as GDA94 or AGD66 and GDA2020 and provided the datum is specified there is no ambiguity in the location.
Updating legal instruments to refer to GDA2020
The legal framework for implementing the national spatial reference system to describe the location of points on the Earth's surface consists of many elements including primary and secondary legislation (Acts and Regulations), policy directives, gazettal’s, standards, specifications and contracts. References to location within regulatory documents generally relate to adminstrative area's defined by coordinates and / or a requirement to provide additional location information in a specific datum.
There is no immediate legal requirment to update regulatory framework documents where the datum is specified as prior national datums can continue to be utilised by virtue of the traceability mechanisms outlined above. For primary and secondary legislation it is understood that such changes may not be made until other amendments are pursued / enacted and similarily existing adminstrative area's defined by coordinates may not be updated to refer to the new datum until there is some other change imperative. However, it is highly desirable that these elements are updated as close as practicable to the Land Tasmania implementation date of 30 September 2020 for adminstrative reasons, particularily where the documented requirement relates to collecting and providing locations in a specific datum (e.g. datum required for plans lodged in the Central Plan Register and / or ongoing use in declaring adminstrative areas, in technical specifications, or development applications).
Defintion of GDA2020 to use in legal documents
ICSM has recommended that the following definitions of GDA2020 and associated map projection MGA2020 be used when updating elements of the legal framework to refer to GDA2020 :
GDA2020 has the same meaning as that contained in the Determination made as to the Recognized-value Standard of Measurement of Position under section 8A of the National Measurment Act 1960 (Cwth)
MGA2020 is the projected coordinate system of rectangular coordiantes derived from a Universal Transverse Mercator projection of latitudes and longitudes based on GDA2020.
Please refer to the ICSM report on legal impacts for further information.