Vertical subdivision
The subdivision of land into lots where boundaries extend from the centre of the earth, through the earths surface to infinity. The plan represents the parcel at the earth's surface.
Stratum subdivision
The division of land 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) or other datum approved by the Surveyor General.
AHD - Australian Height Datum
Is a system of control points for height based on a network of levelling measurements that covered the whole of Australia and was fitted to mean sea level, as measured at tide gauges distributed around the Australian coast, over a period 1968-1970 see clause 5 Surveying and Spatial Information Regulation 2018.
There are several other datums that may be used by surveyors from time to time. In the case where a surveyor does adopt a different height datum the datum used must be clearly identified. See Acceptable Australian Height Datums diagram (GIF 19 KB).
Reduced level
The relative height of a point in relation to a known datum.
Bench Mark
A survey mark used to establish the relative height of a stratum boundary - measured as a Reduced Level AHD.
Subdivision Certificate
Stratum subdivisions must have a 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.