How is natural ground level determined on a previously developed block?
On a previously developed block, natural ground level is determined using the site's Datum Ground Level (DGL), not simply the ground surface that exists today. Where earlier development or earthworks have altered the land, a registered surveyor establishes the best estimate of the original ground surface using available historical survey information and the levels of the surrounding undisturbed land.
If previous building work, excavation or filling has changed the ground, the current ground level is not automatically treated as the original or natural ground level.
A registered surveyor first looks for reliable information showing the ground level from when the subdivision received Operational Acceptance, or, where applicable, from when the first lease was granted before later earthworks occurred.
If that information is unavailable, the surveyor determines a best estimate of the original ground surface. This involves looking at the levels of the immediate surrounding area and identifying areas that have previously been disturbed.
Example: If a previous owner raised part of the backyard with fill, the top of that fill does not automatically become the DGL. The surveyor may reconstruct the likely original ground profile using surrounding undisturbed levels and other available survey evidence.
Reference: Guideline No 3 - Estate Development Plans & Datum Ground Level Surveys - https://www.planning.act.gov.au/__data/assets/pdf_file/0007/2572459/surveyor-general-guideline-03-estate-development-plans-datum-ground-level-surveys.pdf
Link on the answer: https://www.planning.act.gov.au/__data/assets/pdf_file/0007/2572459/surveyor-general-guideline-03-estate-development-plans-datum-ground-level-surveys.pdf
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| Dual Occupancy Q&A | #490 | agrees | 26/08/2026 |