Ground-Penetrating
Radar
High-resolution subsurface imaging from the surface — utilities, voids, pavement layers, archaeological features and more.
Electromagnetic
Pulse Imaging
Ground-Penetrating Radar (GPR) is an active geophysical method that transmits short pulses of electromagnetic energy into the ground and records the two-way travel time of reflections from subsurface boundaries. Reflections occur wherever there is a contrast in dielectric permittivity — the material property that governs how quickly electromagnetic waves propagate through the subsurface.
SGC operates a range of GPR antennae for target depth investigations primarily processed in Geolix — the premier, purpose-built platform for radargram processing, 3D volume rendering, horizon picking and surface generation. This workflow enables delivery of calibrated depth sections, interpolated 3D surfaces and georeferenced utility maps directly from field data.
Antenna frequency selection controls the trade-off between resolution and penetration depth — higher frequencies resolve finer features at shallower depths, while lower frequencies sacrifice resolution to image deeper targets.
Dielectric Properties
& Wave Velocity
The velocity of a GPR wave through a material is governed by its relative dielectric permittivity (εᵣ) — a dimensionless measure of how easily a material is polarised by an electromagnetic field. Water has an exceptionally high permittivity (~80), making moisture content the dominant control on GPR velocity in most soils and rocks.
Depth estimation requires knowledge of the wave velocity in the material being imaged. Velocity is derived from hyperbolic diffraction fitting in the radargram, or applied from test pit samples at designated locations.
The velocity relationship is:
v = c / √εᵣ → depth = v × t / 2
where c = speed of light (0.3 m/ns) and t = two-way travel time. Accurate velocity determination is critical — a 10% velocity error produces a 10% depth error.
| Material | εᵣ | Velocity (m/ns) | Attenuation |
|---|---|---|---|
| Air | 1 | 0.30 | None |
| Ice | 3–4 | 0.16 | Very Low |
| Dry Sand | 3–5 | 0.15 | Low |
| Granite / Limestone | 4–8 | 0.13 | Low |
| Asphalt (dry) | 3–5 | 0.15 | Low |
| Concrete | 6–11 | 0.11 | Low–Med |
| Dry Soil / Loam | 4–6 | 0.13 | Low–Med |
| Moist Soil | 10–20 | 0.09 | Moderate |
| Wet Sand / Gravel | 20–30 | 0.06 | Moderate |
| Saturated Clay | 25–40 | 0.05 | High |
| Seawater | ~80 | 0.033 | Very High |
| Fresh Water | ~80 | 0.033 | Moderate |
What GPR
Is Used For
GPR is one of the most versatile near-surface geophysical methods — applicable wherever a dielectric contrast exists between a target and its host material. Antenna frequency and survey geometry are tailored to each application.
GPR
Workflow
SGC processes all GPR data using a range of software appropriate for the data processing needs albeit the premium software GEOLITIX ensures full compatibility with multichannel acquisition formats and access to the complete processing chain.
All GPR datasets are processed through a structured sequential workflow before spatial assembly and interpretation. Raw traces are conditioned to remove acquisition artefacts, then assembled into georeferenced volumes from which mapped deliverables are extracted.
- Time-zero correction — aligns the air–ground interface to t=0 across all traces
- DC dewow — removes low-frequency drift introduced by inductive coupling
- Bandpass filter — suppresses noise outside the antenna frequency band
- Gain application — SEC or manual gain restores amplitude with depth
- Background removal — subtracts horizontal banding from antenna ringing
- Migration — collapses hyperbolic diffractions to point targets and corrects dip
- Topographic correction — applies GPS elevation data to produce true-depth sections
- 3D volume assembly — all profiles and channels assembled into a georeferenced data volume
- Depth-slice generation — horizontal time/depth slices reveal plan-view target geometry
- Horizon picking — semi-automatic reflector tracking across parallel profile grids
- Surface interpolation — picked horizons interpolated to continuous 3D depth surfaces
- Utility mapping — hyperbola centres extracted and mapped as georeferenced utility lines
- Topographic drape — surfaces draped on DTM for true 3D visualisation
- Export — outputs to DXF, SHP, GeoTIFF, CSV and PDF report formats
Areas We
Serve in Tasmania
Spaulding Geophysics provides comprehensive frequency range ground penetrating radar services across Tasmania, from Hobart and Launceston to regional centres, coastal towns, and remote communities statewide.
Spaulding Geophysics delivers comprehensive frequency range ground penetrating radar services across all of Tasmania — including Hobart, Launceston, Devonport, Burnie, Ulverstone, George Town, Longford, Deloraine, Smithton, Wynyard, Bicheno, St Helens, Scottsdale, Queenstown, Huonville, Kingston, Kettering, Bruny Island and surrounding communities. Remote and regional sites welcomed.