GPR Survey Sydney: Subsurface Imaging for Safer Construction

The GPR survey equipment deployed across Sydney consists of a shielded antenna array mounted on a compact cart, connected to a high-resolution control unit that records reflections from subsurface interfaces in real time. Operators push the system at walking pace over pavement or soil, while the screen displays hyperbolas and layer boundaries that indicate buried pipes, voids, or rebar. A typical scan on a site in the Sydney CBD covers 500 linear metres per day, and the data is processed immediately using RADAN software to produce depth-slice maps. Before mobilising to sites with known fill history, the team calibrates the antenna against a reference target to ensure penetration depth matches local conditions.

Illustrative image of GPR (Ground Penetrating Radar) survey in Sydney

A GPR survey in Sydney can detect a 50 mm PVC pipe at 1.8 m depth in dry sand, but attenuation in wet clay cuts that range by half.

Our service areas

Scope of work

Sydney's coastal geology, with its sequence of Hawkesbury Sandstone overlying Ashfield Shale in the inner suburbs, creates distinct challenges for electromagnetic wave propagation. The sandstone attenuates signals faster than clay, so the GPR survey in Sydney often requires dual-frequency antennas — 400 MHz for deep utility detection down to 4 metres and 900 MHz for shallow slab scanning. Because the water table sits close to the surface in areas like Parramatta and Homebush, the team adjusts gain settings to avoid signal saturation. For projects requiring confirmation of soil stratigraphy, results are cross-referenced with calicatas exploratorias to validate interpreted horizons. When assessing buried infrastructure beneath concrete, capacidad de carga data helps correlate GPR anomalies with structural capacity.

Technical reference — Sydney

Area-specific notes

The sandstone bedrock beneath much of Sydney's eastern suburbs creates a shallow weathering profile where voids and solution cavities can develop along joint planes. A builder excavating for a basement in Paddington recently encountered an unfilled sandstone cavity that was not visible from the surface; a GPR survey performed beforehand would have detected the anomaly as a high-amplitude diffraction hyperbola. Missing such features during pre-construction scanning leads to costly redesigns and schedule delays. The risk is highest in areas where historical mining or quarry backfill remains unmapped, such as the old brickpit zones in Chatswood and the underground quarries beneath Balmain.

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Standards used

AS 1726:2017 Geotechnical site investigations, AS 4678:2002 Earth-retaining structures, AS/NZS 1170.2:2021 Structural design actions

Technical parameters

Parameter	Typical value
Antenna frequency	400 MHz / 900 MHz / 1.6 GHz
Max penetration depth (dry sand)	4.5 m
Max penetration depth (wet clay)	1.2 m
Horizontal resolution	0.1 m at 1 m depth
Survey speed	20–30 m per minute
Data processing software	RADAN 7 / GPR-SLICE

Quick answers

How deep can a GPR survey penetrate in typical Sydney soils?

In dry sand or gravel, a 400 MHz antenna reaches up to 4.5 metres. In wet clay common in western Sydney suburbs, penetration drops to 1.2 metres. The operator selects the antenna frequency based on the target depth and expected soil moisture content.

What is the accuracy of utility location with GPR?

Horizontal accuracy is typically within 0.1 metres at depths up to 1 metre, and vertical accuracy within 0.05 metres for shallow targets. Accuracy decreases with depth and in conductive soils. The survey report includes a confidence rating for each detected feature.

How much does a GPR survey in Sydney cost?

For a standard utility detection survey on a 1,000 square metre site, the cost ranges between AU$1,650 and AU$3,740 depending on access conditions, number of antenna frequencies used, and reporting requirements. Concrete scanning is priced per square metre at AU$8 to AU$15.

Can GPR detect plastic pipes and non-metallic utilities?

Yes, GPR can detect PVC, HDPE, and concrete pipes as long as there is a dielectric contrast between the pipe material and the surrounding soil. The signal reflects off the interface, producing a characteristic hyperbola on the radargram. Metallic pipes produce stronger reflections.

Location and service area

We serve projects across Sydney and its metropolitan area.

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