Definitions (SSIR 2024)

For all survey's completed in accordance with the Surveying and Spatial Information Regulation 2017, please refer to this page.

Vertical subdivision

A conventional subdivision of land into lots whose boundaries extend, theoretically, from the centre of the earth, through the earth’s surface to infinity. The plan represents the parcel at the earth's surface.

Stratum subdivision

The further division of land by horizontal or inclined planes into layers which, when superimposed one upon the other, form the whole of the parcel(s) subdivided. 

Stratum lot

A parcel restricted in height and/or depth by reference to Australian Height Datum (AHD) (as defined below) or other datum approved by the Surveyor General. A stratum lot is bounded by both conventional vertical boundaries and its height and/or depth by horizontal or inclined boundaries.

Australian Height Datum (AHD)

AHD, as defined by Section 3(2) Surveying and Spatial Information Regulation 2024, is a prescribed height datum surface approximating mean sea level that was adopted by the National Mapping Council of Australia in May 1971.
There are a number of other height datums that may be used by surveyors from time to time. The adoption of any height datum other than AHD must be approved by the Surveyor General in accordance with Section 29(1) Surveying and Spatial Information Regulation 2024.

Reduced Level (RL)

The height of a point in relation to a known datum.

Bench Mark

A bench mark is a survey mark of the form and style outlined in Schedule 1 Surveying and Spatial Information Regulation 2024. A stratum survey must relate to 2 or more bench marks that each have accurate AHD values see section 29, 37 and 43 Surveying and Spatial Information Regulation 2024.

Subdivision Certificate

Stratum subdivisions must have a completed Subdivision Certificate.

Residue lots

When a stratum subdivision affects part of a lot in a current plan, the residue lot must be shown in accordance with clause 25 Conveyancing (General) Regulation 2018.