National Measurement (Recognized-Value Standard of Measurement of Position) Determination 2017

The determination uses a small set of technical legal concepts to convert scientific realisation into a legal recognised-value standard. The principal concepts are: recognised-value standard of measurement, Reference Ellipsoid, Reference Epoch, Reference Frame, coordinates with uncertainties, and an epoch propagation model.

Recognized-value standard of measurement is a term defined in the National Measurement Act 1960. In this instrument the phrase is used in s 6(1) to refer to the positions listed in Schedule 1, within the specified Reference Ellipsoid and Reference Frame. The legal effect is that the listed values are the official, metrologically traceable reference for the physical quantity position for the AFN.

Reference Ellipsoid is the geometric model of the Earth used for converting between Cartesian coordinates and geodetic (latitude, longitude, ellipsoidal height). The determination specifies GRS80, including its exact semi-major axis and inverse flattening (s 4). Section 6(3) requires use of that ellipsoid for conversion from global Cartesian coordinates to latitude, longitude and ellipsoidal height.

Reference Epoch is the temporal origin for the tabulated coordinates. The instrument sets Reference Epoch 2020.0 (s 4). Because geodetic positions drift through tectonic or plate-scale motion and other secular processes, an epoch anchors the static coordinate values to a particular time. The determination therefore supplies coordinates valid at 2020.0 and a velocity field to propagate those coordinates to other epochs.

Reference Frame, as defined in s 4, is GDA2020 realised by the AFN coordinates referred to ITRF2014 at the Reference Epoch. This links the national realisation to an international terrestrial reference frame (ITRF2014). By referring the realisation to ITRF2014 the determination aligns Australia’s legal geodetic reference to internationally maintained frames and their time-dependent realisations.

Coordinates, uncertainties and velocities: Schedule 1 carries numerical values for X, Y, Z (metres) at epoch 2020.0; uncertainties u(X), u(Y), u(Z) (metres); velocities VX, VY, VZ (metres per year) and velocity uncertainties u(VX), u(VY), u(VZ). The instrument identifies the uncertainties as expressing 95 per cent confidence intervals (s 6(2). The velocity components permit linear epoch propagation.

Epoch propagation model: Section 7 prescribes a linear model to compute global Cartesian coordinates of the AFN at an epoch t (years) by using the Schedule 1 coordinates and velocities. The instrument states the model is valid for 15 years either side of 2020.0 (s 7). The practical implication is that users must apply the supplied secular velocity components and the epoch offset when deriving coordinates for dates other than 2020.0, and they must bear in mind the stated validity window.

Schedules are part of the instrument. Schedule 1 contains the AFN realisation numeric table and Schedule 2 repeals the 2012 determination in whole. The instrument also contains notes referencing external technical sources: IUGG for GRS80, ICSM for GDA2020 technical information, and IERS for ITRF2014 (s 4 notes). These notes are presented as references rather than normative inclusions.

Together the concepts convert metrological traceability , a scientific realisation of coordinate values with quantified uncertainty , into a legally recognised-value standard that other instruments, instruments of measurement traceability and legal instruments can refer to.

This determination primarily affects entities that rely on legally recognised coordinate references for surveying, cadastral work, mapping, geospatial data management, engineering, construction, mining, transport navigation, GNSS service provision and government spatial infrastructure.

• Surveyors and cadastral authorities: the instrument provides the official AFN realisation in GDA2020 at epoch 2020.0. Survey practice that requires traceable reference coordinates, especially work that interacts with land titling, boundary determination or official mapping, will be affected because the Schedule 1 values are the recognised-value standards of measurement for AFN geodetic stations (s 6(1)).

• State and local government spatial agencies: organisations responsible for maintaining state positional reference networks, spatial data infrastructures and coordinate transformations will need to adopt the Reference Ellipsoid (GRS80), Reference Frame (GDA2020 realised by the AFN and referred to ITRF2014) and the epoch propagation model to ensure consistency with the national legal standard (s 4, s 6, s 7).

• GNSS and positioning service providers: providers that deliver positioning corrections, network real-time kinematic services (RTK), precise point positioning, or transformation grids must align their frame realisations and transformation parameters with the AFN recognised values if they wish to present coordinates traceable to the national standard. The determination specifies that coordinates are referred to ITRF2014 at epoch 2020.0 (s 4).

• Engineering, construction and mining firms: projects that rely on high-accuracy control networks, design transfer and machine guidance will be affected because the instrument provides the legal reference coordinates and requires epoch propagation; practitioners must ensure their project control is consistent with the declared GDA2020 realisation and its epoch (s 6, s 7).

• Data custodians and GIS operators: organisations that maintain spatial databases, cadastral records or property mapping should note the Reference Ellipsoid and epoch so their coordinate storage, metadata and conversion routines are consistent with the recognised-value standards (s 4, s 6(3)).

• Academic and research users: geodesists, geophysicists and applied researchers who rely on national reference coordinates will be affected by the shift to epoch 2020.0 and by the linkage to ITRF2014, which may affect time-dependent analyses.

Who decides and who pays: the Chief Metrologist at the National Measurement Institute makes the determination (instrument header and s 3). Costs of compliance fall on users: updating software, transformation parameters, metadata, retraining staff, and possible re-surveying of control points to align to the new legal realisation. These are private and agency costs; the instrument itself does not set funding arrangements.

Who is not directly affected: casual consumers of location-based services are unlikely to notice day-to-day effects, because most consumer GNSS services use WGS84-derived coordinates and approximate transformations; however, professional users depending on legal traceability must align practice to this instrument.

Finally, the instrument repeals the 2012 determination (Schedule 2). Entities that adopted the 2012 recognised values must transition to the 2017 determination’s GDA2020 realisation and epoch. That repeal is a legal change of the recognised standard and therefore affects long-term contractual or statutory references to the earlier recognised-value instrument.

The determination sets out legal duties principally by establishing what counts as the recognised-value standard of measurement for AFN positions, and by prescribing the required methods for conversion and epoch propagation. It does not, within the instrument’s text, create administrative offences or penalties; those are governed by the National Measurement Act 1960. The key operative duties and rights found in the instrument are the following.

Duty to use the specified Reference Ellipsoid for conversion: Section 6(3) requires that for conversion from global Cartesian coordinates to latitude, longitude and ellipsoidal height the Reference Ellipsoid (GRS80) must be used. That is a clear procedural duty on any party converting Cartesian AFN coordinates to geodetic coordinates if they rely on the recognised-value standard.

Duty to rely on Schedule 1 for recognised values: Section 6(1) declares that the positions listed in Schedule 1, in the stated Reference Ellipsoid and Reference Frame, are the recognised-value standards of measurement of the physical quantity position for AFN geodetic stations. Users who must conform to national recognised values for legal, regulatory or contractual reasons therefore must adopt those tabulated coordinate values and their stated realisation.

Duty to interpret uncertainties as 95 per cent confidence intervals: Section 6(2) specifies that the listed uncertainties are such that X ± u(X) represents a 95 per cent confidence interval. This is a metrological duty: when reporting or using the uncertainties from Schedule 1, users must treat them as representing 95 per cent coverage probabilities.

Duty to apply the linear epoch propagation model and observe its validity window: Section 7 provides the authorised linear model for expressing AFN Cartesian coordinates at an epoch t (years) using the Schedule 1 coordinates and velocities. The instrument also makes explicit that the model is valid for 15 years either side of the Reference Epoch (s 7). Practitioners must therefore apply the linear model when propagating coordinates to other epochs, and they must observe the 15-year validity window for reliance.

Right to legal traceability: By designating the Schedule 1 values as recognised-value standards, the determination gives users a legally traceable realisation. Parties seeking metrological traceability for measured position now have an instrument-based standard to cite. This is a right in the sense that the instrument provides an authoritative reference that can be used to demonstrate compliance with measurement traceability requirements.

No procedural duties in the instrument for third parties: The instrument itself does not specify registration, notification or approval processes for third parties. It is declarative. Any duties to register or certify instruments, or to use particular transformation parameters in statutory contexts, would derive from other legislation, regulation, or procurement contracts rather than from this determination itself. The instrument is a legal declaration of values and methods; it is not a licensing regime.

Transition duty implied by repeal: Schedule 2 repeals the 2012 determination in whole. Entities that previously relied on the 2012 recognised values will have to transition to the 2017 Schedule 1 values and methods where legal reliance on the national recognised standard is required.

In practical terms, the determination changes the de facto duties of practitioners who need to demonstrate traceability to the national standard: they must use the GDA2020 realisation referred to ITRF2014 at epoch 2020.0, use GRS80 for conversions, apply the linear velocity model for epoch propagation, and interpret uncertainties as 95 per cent confidence intervals (s 4, s 6, s 7).

The determination itself does not set out specific penalties or enforcement mechanisms within its text. It is made under the authority of the National Measurement Act 1960 (s 3), specifically section 8A(1), and functions as a determination of recognised-value standards. The instrument declares standards and prescriptive methods, but does not, in its provisions, assert enforcement procedures, offences or civil remedies.

Consequently the legal enforcement regime relevant to this determination, including any errors, misuse of recognised-value standards, or non-compliance, would be governed by the National Measurement Act 1960 and any regulations or other statutory instruments made under that Act. This instrument does not reproduce or restate such enforcement provisions. Practitioners requiring clarity on penalties or compliance obligations therefore must consult the National Measurement Act 1960 and associated regulations for offences, liability, inspection powers and enforcement processes.

Two practical points for users regarding enforcement and risk:

• Reputational and contractual consequences: Even in the absence of specific sanctions in the instrument, failing to adopt the recognised-value standards where a party’s work is legally, contractually or administratively required to be traceable to national standards may create contractual liability, professional discipline or tendering consequences. Surveyors, contractors and agencies that are required by statute, contract or professional rules to provide measurements traceable to national standards will likely face risk if they use non-recognised values without agreement.

• Technical risk and reliance horizon: The instrument sets a 15-year validity window either side of the Reference Epoch for the linear epoch-propagation model (s 7). Using the linear model outside that window increases technical and legal risk because the instrument does not endorse such extrapolation. Users who disregard the stated validity period may lack a recognised standard to reference for measurements outside that period.

Because the instrument is a determination under the National Measurement Act, any formal questions about compliance, inspections, adjudication or penalties should be directed to the Act and its administrators. The instrument itself is declaratory technical law: it specifies standards, conversion rules and uncertainties; enforcement of correct measurement practice is a matter for the general regulatory framework under the Act rather than the determination’s text.

The determination operates within a legal ecosystem that includes the National Measurement Act 1960 and sectoral laws that reference or depend on legal standards of position. The instrument explicitly states its statutory authority under section 8A(1) of the National Measurement Act 1960 (s 3). It repeals the previous recognised-value instrument from 2012 (Schedule 2). Beyond that, the determination interacts with other laws and technical frameworks by supplying the legal reference that those laws and regulations, or contracts and procurement arrangements, may reference.

Reference to the National Measurement Act 1960: The instrument is an exercise of the Chief Metrologist’s power to determine recognised-value standards. The Act governs metrology in Australia, including how recognised-value standards are to be made, and sets the broader regulatory context. The determination does not restate the Act, and it does not specify enforcement provisions; those remain in the Act.

Cadastral and land law consequences: State land titling and cadastral systems commonly rely on a national datum and recognised geodetic references. Where state statutes, land registries or cadastral rules require measurements traceable to national standards, those instruments now will point to the values and methods in Schedule 1 and to GDA2020 as the national realisation. The determination therefore provides the national referent for any statutory or regulatory scheme that requires traceable positional measurements, although the determination itself does not amend state statutes.

Relations with international realisations and technical bodies: The Reference Frame is GDA2020 realised by AFN coordinates referred to ITRF2014 at the Reference Epoch (s 4). That links domestic legal standards to an international technical system maintained by the International Earth Rotation and Reference Systems Service (IERS). The instrument’s notes reference IUGG for GRS80 and ICSM for GDA2020 technical material. In practice, this means Australian law recognises a national realisation that is explicitly tied to an international frame, which is relevant where cross-border data, international navigation or scientific comparability are required.

Interactions with GNSS and WGS84: The instrument mandates GRS80 for conversions (s 4 and s 6(3)). WGS84 and GRS80 are closely related but not identical. Laws or contracts that explicitly require WGS84 coordinates will need careful treatment where traceability to GDA2020 (GRS80 ellipsoid) is required. Practitioners must ensure they are using the correct ellipsoid and any specified epoch or transformation methodology to reconcile references to WGS84, ITRF2014 and GDA2020.

Contractual references and procurement: The determination affects contracts or procurement specifications that reference recognised-value standards of position. If a contract required compliance with the 2012 determination, Schedule 2’s repeal means that, in the absence of contractual amendment, parties must clarify whether compliance is to the new 2017 determination, or whether the contract’s reference to a now-repealed instrument creates ambiguity. Users should consider amending contract language to reference the current recognised-value standard and its epoch.

No express displacement of other laws: The instrument does not purport to displace other substantive laws. Instead, it provides the national metrological standard to which other laws, regulations and contractual requirements can refer. It does not, by its text, create or remove property rights, registration processes or cadastral boundaries; those effects occur through the operation of other laws that adopt or require traceability to the national standard.

In short, the determination supplies the legally recognised AFN realisation to be used where Australian law, regulations or contracts require traceability of positional measurements. Practitioners should check sectoral legislation, cadastral rules and contract terms to see how the new recognised-value standard must be applied in specific legal contexts.

The instrument itself contains a concise internal amendment history. It is the National Measurement (Recognized-Value Standard of Measurement of Position) Determination 2017, dated 11 October 2017 and stated to commence the day after registration (s 1, s 2). The authority for the instrument is section 8A(1) of the National Measurement Act 1960 (s 3).

The only express amendment recorded inside the instrument is the repeal of the previous recognised-value determination from 2012. Schedule 2 is titled Repeals and contains a single item: the whole of the Recognized-value standard of measurement of position 2012 (No. 1) is repealed (Schedule 2). That is a full repeal rather than a partial amendment, replacing the 2012 legal realisation with the 2017 recognised values and methods.

There are no other schedules that amend existing instruments. Section 5 explains the normal operation of schedules: each instrument specified in a schedule is amended or repealed as set out in the applicable items, and any other item in a schedule has effect according to its terms (s 5).

Contextual chronology and technical evolution: Although the instrument does not narrate a broader legislative amendment timeline, its content shows a technical evolution in Australia’s national datum policy. The Reference Epoch is 2020.0, and the Reference Frame is GDA2020 referred to ITRF2014. Historically, Australia used GDA94 as a principal geodetic datum; the 2012 determination and this 2017 determination are successive steps in updating the national realisation. The 2017 instrument supersedes the 2012 instrument, marking an update of the recognised-value technical realisation and its epoch. The instrument’s notes point practitioners to technical background material hosted by the ICSM and IERS, and the instrument anchors the legal standard in the contemporary international reference (ITRF2014).

Administrative details: The instrument is signed by Dr R. Bruce Warrington, Chief Metrologist, and dated 11 October 2017. The formal commencement clause (s 2) makes the instrument operative the day after registration, so the effective date depends on the registration date in Commonwealth Gazette or the relevant register.

Future amendments: The instrument does not state a mechanism for future amendment beyond the general power in the National Measurement Act. Any future change to the recognised-value standards or the Reference Frame, Epoch or Ellipsoid would require a further determination under the Act. Users who rely on the national standard should therefore watch for subsequent determinations or regulations that amend Schedule 1, change the Reference Epoch, or adopt a later ITRF realisation.

The determination itself contains no litigation history. It is a technical legal instrument and does not reference any case law, disputes or adjudications within its text. Schedule 2 repeals the 2012 determination, but the instrument records no judicial consideration of either the 2012 instrument or the 2017 replacement.

For practitioners seeking litigation precedent about the legal status or interpretive issues of recognised-value determinations, the instrument offers no internal guidance. Any litigation history relevant to the National Measurement Act 1960, its administration, or disputes over metrological determinations must be sought in external legal databases or reported cases interpreting the Act or its subordinate instruments. This determination does cite international technical references (IUGG, ICSM, IERS) as notes, but those are technical references rather than legal precedents.

Practical implications relating to litigation risk:

• Evidential primacy: Because the instrument declares the Schedule 1 values to be recognised-value standards of measurement of position (s 6(1)), those values will carry evidential weight in disputes where parties assert compliance or non-compliance with national metrological standards. Absent contrary statutory provisions, a court or tribunal is likely to treat the instrument as an authoritative statement of the national standard. The instrument itself contains no jurisprudential discussion, so litigators will need to frame arguments about admissibility, weight and application of recognised values around the statute and relevant case law.

• Uncertainties and expert evidence: The instrument specifies that the uncertainties in Schedule 1 correspond to 95 per cent confidence intervals (s 6(2)). In litigation involving positional accuracy, experts should apply those uncertainty definitions when opining on measurement reliability and error bounds. The instrument therefore sets a metrological baseline that will be material to expert evidence.

• Epoch propagation and temporal issues: Because the instrument prescribes a linear epoch-propagation model and limits its validity to 15 years either side of the Reference Epoch (s 7), disputes that hinge on coordinates expressed at dates beyond that validity window will require careful technical and legal argument. Parties relying on propagated coordinates outside the stated window may face challenges about whether their methodology was consistent with recognised standards.

• Repeal and continuity: The full repeal of the 2012 determination (Schedule 2) may be relevant in disputes where older records or contracts explicitly referenced the 2012 recognised values. Litigators should examine whether contractual language or statutory references created obligations to adhere to the now-repealed instrument, and how to treat such obligations after repeal.

To determine whether any litigation has actually been brought against or related to this determination, practitioners must search legal databases, tribunal records and relevant administrative decisions. The determination’s text does not record litigation history, and the instrument names no cases.

This instrument is technical and deceptively simple. Practitioners should be aware of a number of risks, traps and practical constraints embedded in the text.

Epoch and validity window: The Reference Epoch is 2020.0 and the linear epoch-propagation model in s 7 is valid for 15 years either side of that epoch (s 7). That yields a recommended validity window from 2005.0 to 2035.0. Users who extrapolate coordinates beyond that window will be relying on methods not endorsed by the instrument. The instrument does not provide alternate propagation models for longer time frames, nor does it provide a formal procedure for updating velocities. Users requiring long-term extrapolation must either seek an updated determination or adopt more sophisticated geophysical models, but those would not be the instrument’s recognised standard.

Obligation to use GRS80 for conversions: Section 6(3) requires use of the Reference Ellipsoid (GRS80) for conversion from Cartesian to geodetic coordinates. Some software, services and technical teams default to WGS84 or to epochless transformations. Because the instrument mandates GRS80, using a different ellipsoid without explicit conversion steps will produce coordinates not consistent with the recognised-value standard. GRS80 and modern realizations of WGS84 are close but differ at levels material for high-precision surveying. This is a technical gotcha for teams that assume WGS84 automatically equals the national ellipsoid.

Tie to ITRF2014 and GDA2020: The Reference Frame is GDA2020 realised by the AFN coordinates referred to ITRF2014 at the Reference Epoch (s 4). If your GNSS processing is tied to a later ITRF realisation or to a different epoch, you must apply correct transformations and epoch propagation to be consistent with the instrument. Using ITRF2008 or ITRF2020 without careful transformation will mean your outputs are not the recognised values the instrument declares.

Uncertainties are 95 per cent intervals: The instrument defines uncertainties as 95 per cent confidence intervals (s 6(2)). Some practitioners and software treat reported uncertainties as one-sigma (68 per cent) by default. Misinterpreting the uncertainty coverage will lead to inconsistent statements of measurement quality and potential misrepresentation in technical reports and legal submissions.

Replacement of the 2012 determination: Schedule 2 repeals the 2012 determination in whole. Contracts, legislation or administrative practices that still reference the 2012 instrument may now be unclear. Unless a contract specifies that the reference is to "the determination as in force at the time" or locks in the older numbers, parties should expect that the national recognised standard is now the 2017 instrument’s Schedule 1 values. Contract drafters and litigators should check whether older references require explicit updating.

Numerical precision and rounding: Schedule 1 lists coordinates and velocities with numerical precision to sub-millimetre or sub-centimetre digits and velocity uncertainties often to 1e-4 m/yr. Software rounding, CSV export/import, or third-party GNSS services that truncate or reformat numbers can introduce offsets larger than the listed uncertainties. Practitioners must ensure their data pipelines preserve sufficient precision to maintain traceability to the recognised values.

Coverage and completeness: The instrument lists many AFN sites, but it is limited to those stations in Schedule 1. Positions for other stations or control points are not declared recognised-value standards by this instrument. Users should not assume that non-AFN stations are covered. If a project requires traceable coordinates for other points, those points must be tied to the AFN realisation by appropriate surveying and metrological practice.

Interpretation of the linear model: The instrument prescribes a linear model for epoch propagation (s 7). Linear models do not capture transient effects such as post-seismic deformation, local subsidence, or other non-linear motions. In areas affected by such processes, reliance on the simple linear model could yield materially wrong positions within the 15-year window. The instrument does not address these localised phenomena; practitioners must apply local geophysical knowledge when appropriate.

No penalties specified: The instrument does not define offences or penalties. Users should not assume that non-use of the recognised values is harmless; legal, contractual and professional consequences may flow from failing to meet traceability obligations in other statutes, regulations or contracts.

Finally, administrative timing: The instrument is dated 11 October 2017 and commences the day after registration (s 1, s 2). Practitioners must note the formal commencement in the register to know the precise date the recognised values became authoritative for legal traceability.

Compliance with this determination is essentially procedural and technical: use the declared recognised values, apply the prescribed conversion and propagation methods, and maintain documentation and traceability that demonstrates conformity to the instrument’s prescriptions.

1. Adopt the Reference Ellipsoid and Reference Frame

   • Use the GRS80 ellipsoid parameters as specified in s 4 for any conversion between Cartesian coordinates and latitude, longitude and ellipsoidal height. Ensure geodetic software is configured to use the exact semi-major axis a = 6 378 137 metres and inverse flattening 1/f = 298.257 222 101.
   • Treat the Reference Frame as GDA2020 realised by the AFN coordinates referred to ITRF2014 at epoch 2020.0 (s 4). Where software or services default to other frames, explicitly specify GDA2020/ITRF2014 and epoch 2020.0.

2. Use Schedule 1 values as the authoritative AFN realisation

   • When your work requires traceability to the national recognised-value standard, use the coordinates, uncertainties and velocities as listed in Schedule 1. Store the full numeric precision available in the Schedule so that your derived coordinates remain traceable within the stated uncertainties.
   • Record the provenance: cite this determination by name and section where relevant in project reports, certificates, survey plans and metadata to demonstrate that measurements are traceable to the recognised national standard.

3. Apply the epoch propagation model and observe its validity

   • Propagate coordinates to an epoch t (years) by applying the linear model set out in s 7 using the tabulated coordinate components and velocities. Practically, compute coordinate(t) = coordinate(2020.0) + velocity * (t − 2020.0). Use the velocity components VX, VY, VZ from Schedule 1 and maintain the same unit conventions (metres and metres per year).
   • Do not rely on the linear propagation model outside its stated validity window: 15 years either side of the Reference Epoch (s 7). For epochs outside that window, obtain an updated determination or adopt technically justified alternative models only with documented reasons and stakeholder agreement.

4. Treat uncertainties as 95 per cent confidence intervals

   • When reporting positional uncertainty, use the u(X), u(Y), u(Z) values as 95 per cent confidence intervals (s 6(2)). If your internal practice reports one-sigma uncertainties, convert appropriately or explicitly document the difference. Use the velocity uncertainties similarly when reporting confidence bounds for propagated velocities.

5. Ensure software, datasets and transformation chains preserve precision and metadata

   • Configure GNSS processing software, GIS, CAD and surveying systems to preserve the numerical precision in Schedule 1. Avoid truncation or format changes that lose significant digits.
   • Include metadata fields that record: the determination name and date, Reference Epoch 2020.0, Reference Ellipsoid (GRS80), Reference Frame (GDA2020 realised by AFN referred to ITRF2014), and whether coordinates have been propagated from 2020.0 and the propagation epoch used.

6. Review contractual and statutory references

   • If contractual documents, procurement specifications or statutory requirements reference the earlier 2012 determination, update or clarify these references to the 2017 determination where appropriate. Schedule 2 repeals the 2012 instrument in whole; contracts that uncritically point to the 2012 instrument may require amendment to reflect the current recognised standard.

7. Consider local geophysical effects

   • Where local non-linear motions are known or suspected (for example post-seismic deformation, mining-induced subsidence or very localised ground movement), supplement the linear propagation model with local geophysical modelling or local control observations. Document the rationale and the limitations of the recognised-value linear model in such cases.

8. Maintain chain of custody and traceability documentation

   • For cadastral surveys, engineering control work and other regulated activities that require measurement traceability, maintain records that show how AFN values were used, how epoch propagation was applied, and how conversions to latitude/longitude/height were performed using GRS80. Include references to the determination (identify s 6 and s 7 where relevant) in evidentiary materials.

9. Stay informed of updates

   • The instrument is a determination under the National Measurement Act and may be updated by subsequent determinations. Monitor the National Measurement Institute publications and relevant ICSM or IERS announcements for new realisations, updated epochs, or revised velocities. Plan projects so that changes in the national realisation do not create avoidable rework.

10. Seek expert advice when uncertain

    • If you are unsure how to apply the instrument in complex situations, such as multi-epoch datasets, integration with non-AFN control, or legal disputes about datum realisation, engage a professional geodesist or the National Measurement Institute for authoritative advice.

By following these steps you will align practical measurement procedures with the legal recognised-value standard set out in the determination, maintain metrological traceability and reduce legal and technical risk when positional measurements are relied upon in statutory, contractual or evidentiary contexts.