ACT site data into Civil 3D and QGIS: a worked example

Setting up a Canberra infill site in Civil 3D or QGIS means getting three things into the model in the right order: the lot boundary (cadastre), a working surface (contours or a DEM), and the planning context (the Territory Plan zone and any overlays). This worked example follows one hypothetical sloping suburban block in a Canberra inner-north suburb from first download to a usable design base. The site, the slope figures and the setbacks below are illustrative, chosen to show the steps, not a real lot.

The ACT differs from the states in two ways that matter here. All residential land in Canberra is Crown leasehold, so the thing you draw a boundary around is a leased block defined by a Deposited Plan, and the "ownership" is a Crown lease with a purpose clause. And zoning comes from the Territory Plan, administered through a single agency, with the mapping served on ACTmapi. Both affect how you read the data you export.

The site and the brief

The brief: a dual-occupancy feasibility on a single residential block in an established inner-north suburb, falling from the street at the rear to the front boundary. The ground drops roughly three to four metres across the block. Early questions are whether the fall forces split levels or a step in the slab, where the existing fall sends stormwater, and what the Territory Plan zone and any overlays allow before anyone pays for a feature survey.

None of this is a substitute for a registered surveyor's feature and level survey or a site classification to AS 2870. The desktop model sets expectations and scopes the field work. It does not replace it.

Step 1: Get the cadastre and confirm the lease

Start with the block boundary, because every other layer is positioned against it.

Pull the lot boundary

Export the cadastre for the address as a vector dataset. For boundary work, a Shapefile or GeoPackage drops straight into QGIS with attributes intact, and a DXF opens in Civil 3D as closed polylines you can set as a boundary or an alignment reference. The block and section number and the Deposited Plan reference travel in the attributes, so keep the GeoPackage alongside the DXF rather than discarding it.

Read the lease purpose

In the ACT the cadastre tells you the block geometry, but the Crown lease purpose clause controls what the land may be used for, and it can be more restrictive than the Territory Plan zone. A block zoned to allow dual occupancy can still carry a lease that permits a single dwelling only, which would need a lease variation. Confirm the lease conditions before the dual-occupancy feasibility goes further. The exported cadastre gives you the identifiers to look the lease up; it does not contain the lease clause itself.

If the boundary matters for setbacks or a party-wall arrangement, treat the online cadastre as indicative and have it confirmed. The difference between a mapped boundary and a surveyed one is set out in property boundary map: online vs survey.

Step 2: Choose contours or a DEM for the surface

With the boundary in, decide what elevation data you need for an early feasibility.

Dataset	Format out	Best for
Vector contours	DXF, Shapefile, GeoPackage, KMZ	Drafting, quick fall checks, a drawing base
DEM (raster elevation)	GeoTIFF	Surfaces, cut and fill volumes, slope analysis
TIN surface	DXF only	Dropping a ready-made surface into Civil 3D

For this feasibility, contours at a sensible interval answer the first question (does the fall force split levels) and give the drafter a base. A one-metre interval reads cleanly on a three-to-four-metre block; a half-metre interval shows the subtle grading you need for a driveway crossover and overland flow. If the next step is cut-and-fill volumes, bring in the DEM as a GeoTIFF and build a surface from it. Choosing between vector contours and raster elevation is covered in contours or DEM?, and picking an interval in choosing the right contour interval.

Load it in Civil 3D

Import the DXF contours, or create a surface from the GeoTIFF. Set the drawing's coordinate system first. Current ACT datasets are published in MGA2020 (the national grid, using GDA2020). Set that before you bring anything in, so the cadastre, contours and later the survey all stack in the same place. Not every input will be in it, though: check the horizontal CRS in each file's metadata, and transform older data on AGD66 or the ACT's Standard Grid Coordinates (SGC) to MGA2020 rather than simply assigning MGA2020 to it. MGA2020 only fixes the horizontal position, though. ACT LiDAR and elevation products can carry heights in AHD (Australian Height Datum, metres above mean sea level), ellipsoidal heights or AVWS (the Australian Vertical Working Surface), and a non-AHD surface will not line up in height with an AHD survey. Check the vertical datum in the elevation file's metadata and use an AHD product for this workflow. The two kinds of mismatch show up differently: a wrong horizontal CRS or projection shifts layers in plan, often by hundreds of metres, while a wrong vertical datum leaves everything in the right place but puts the heights out by an offset (about 20 m between ellipsoidal and AHD heights around Canberra, a few tenths of a metre between AVWS and AHD). Both are among the traps in eight mistakes importing site data.

Load it in QGIS

In QGIS, set the project CRS to GDA2020 / MGA Zone 55, which covers the ACT. Add the GeoPackage cadastre and the contours or GeoTIFF. A quick slope or hillshade render off the DEM confirms the direction and steepness of the fall before you commit to a design approach.

Step 3: Read the Territory Plan zone and overlays

Now bring in the planning context. The feasibility lives or dies on what the zone and overlays allow.

The Territory Plan assigns a zone (for residential land, the RZ zones from RZ1 to RZ5, with RZ1 Suburban the most common in established areas). The zone sets the development controls: permitted uses, plot ratio, building height and setbacks. An RZ1 block has tighter controls on additional dwellings than an RZ2 block, so for a dual occupancy this single reading can change the whole feasibility.

Check the zone and the overlays on ACTmapi, the Territory's planning map. A step-by-step walkthrough of finding a block, its zone and its overlays is in the ACTmapi guide. Watch for:

• Zone. RZ1 to RZ5. Confirm the exact RZ before testing yields.
• Bushfire prone area. Canberra's western and southern edges carry bushfire mapping. The map shows where bushfire risk is mapped; it does not assign a Bushfire Attack Level to a block. Where the block is mapped, get a site-specific bushfire assessment to set the BAL and the construction requirements that follow.
• Flood and drainage. Blocks near an urban creek or an overland flow path can sit under a drainage or flood constraint. Your own DEM check from Step 2 should agree with the mapped flow direction; if it does not, something in the data needs a second look.
• Heritage. Several inner-north and inner-south precincts carry heritage listings that constrain demolition and form.

Bring the zone and overlay boundaries into the model as vector layers (Shapefile, GeoPackage or KMZ) so setbacks and constrained areas sit over the cadastre and the contours together, not in three separate windows.

What each finding changed

At the end of the desktop set-up for this illustrative block:

• The three-to-four-metre fall confirmed a stepped slab or split level, which the feasibility now assumes rather than guesses.
• The DEM showed overland flow crossing the front corner, flagging a drainage question for the civil design and a point to confirm on survey.
• The RZ zone and the lease purpose clause together decided whether the dual occupancy is a planning question, a lease-variation question, or both.

None of these replaces field work. They tell the surveyor and the geotechnical engineer where to look, and they stop the feasibility running on assumptions that the data could have corrected on day one.

When you need the Canberra cadastre, contours, DEM and planning layers for a block without stitching tiles and reprojecting by hand, export site data for any address or see a sample export to check the formats against your workflow first.

LayeredGeo lets you download site data for Queensland, New South Wales, Victoria, South Australia, the ACT and Tasmania - contours, cadastre and more - in DXF, Shapefile, GeoPackage, KMZ and raster formats, ready for Civil 3D, QGIS and ArcGIS.

About this article. Published by LayeredGeo. It is general information about how property and ground conditions are assessed in Australia, not engineering, planning, legal or financial advice, and it is not specific to any property. Check anything that matters against the source dataset or a suitably qualified professional before you rely on it. If you spot something wrong, tell us at hello@layeredgeo.com.au and we will fix it.

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