Legal Traceability


Legislative Requirements Pertaining to Legal Traceability of Length for Cadastral Surveying

The necessity for demonstration of legal traceability in the context of cadastral surveying arises from section 12A(1) of the National Measurement Act 1960 which provides that:
    "After the commencement of this section, every contract, dealing or other transaction made or entered into with respect to an interest in land that refers to any measurement of a physical quantity (including a reference to a measurement of a physical quantity for descriptive purposes only) shall refer to Australian legal units of measurements of that physical quantity."
Section 10 of that Act provides that:
    "When, for any legal purpose, it is necessary to ascertain whether a measurement of a physical quantity for which there are Australian legal units of measurements has been made or is being made in terms of those units, that fact shall be ascertained by means of, by reference to, by comparison with, or by derivation from:.........(c) an appropriate State primary standard of measurement;.........(e) an appropriate reference standard of measurement;........."
Section 10 thus establishes that the legal traceability of measurements made by any particular working tape or measuring instrument may be established by direct comparison of measurements made with any such tape or instrument, with any one of a potential number of certified reference standards of measurement. It should be noted that such working tapes or instruments are not themselves required to be verified under the Act as reference standards.

Section 3 of the Act includes the following definitions, an understanding of which is essential in correctly interpreting the previously referred provisions:
    "reference standard of measurement" means a standard of measurement (other than an Australian primary standard of measurement, an Australian secondary standard of measurement, a recognised-value standard of measurement or a State primary standard of measurement) that has been verified in accordance with the regulations."

    "standard of measurement" means:
    "(a) a material measure, measuring instrument or measuring system designed or intended to define, realise, conserve or reproduce:
      (i) a unit of measurement of a physical quantity;
      (ii) one or more known values of a physical quantity;
    in order to transmit that unit or those values to measuring instruments by way of comparison; ........."
An understanding of this particular definition is vital in that it provides that every reference to "a standard, or standards of measurement" in the Act must be interpreted as a reference to a specific physical measure, instrument or system, and not in a generic sense as an expression denoting the particular quality or adequacy of a measurement.

Division 2 of the National Measurement Regulations 1999 further provides for the appointment of verifying or certifying authorities that, in the opinion of the Chief Metrologist, are capable of verifying a reference standard of measurement.

The significance of the foregoing provisions is that while verification of a reference standard of measurement may only be provided by an approved verifying authority, such authority is not necessary to establish the legal traceability of any working tape or measuring instrument as long as practical provision can be made for direct comparison of such measuring devices with an appropriate reference standard of measurement.

This interpretation of the statutory provisions has been confirmed by the National Standards Commission [letter to Office of the Surveyor General, 23 January 1995].

The matter of the establishment and maintenance of facilities providing for such comparisons is beyond the scope of Commonwealth Act. It therefore falls to the State to ensure compliance through the inclusion of appropriate provisions in all relevant State legislation and the maintenance of whatever comparison facilities may be deemed appropriate in order to satisfy the traceability requirement.

In the particular case of measurement of length for cadastral survey purposes, this requirement is addressed under the Survey Directions Pursuant to the Surveyors Act 2002, which require all equipment to be regularly calibrated and standardised by comparison with a National Reference Standard of Length verified under the National Measurement Act 1960.


Office of the Surveyor General

134 Macquarie Street,
HOBART, TAS, 7000.