Ground Penetrating Radar operates similarly to a sonar. A tiny pulse of energy is emitted into the ground, recording the strength and time it takes for the signal to return from the reflected object. This signal is exhibited on a visual screen and allows for the accurate detection of buried underground objects; regardless of their composition. Limitations of this method include, but are not limited to landscaping, heavy underground debris and limited accessibilities to areas.
GPR works by sending a tiny pulse of energy into the ground and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area make up what is called a scan. Reflections are produced whenever the energy pulse enters into the ground with different electrical conduction properties or dielectric permittivity from the material it left. Each material has a different dielectric property.
The strength, or amplitude, of the reflection is determined by the contrast in the dielectric constants and conductivities of the two materials. This means that a pulse which moves from dry sand (dielectric of 5) to wet sand (dielectric of 30) will produce a very strong reflection, while moving from dry sand (5) to limestone (7) will produce a relatively weak reflection.
While some of the GPR energy pulse is reflected back to the antenna, energy also keeps traveling through the material until it either dissipates (attenuates) or the GPR control unit has closed its time window. The rate of signal attenuation varies widely and is dependent on the properties of the material through which the pulse is passing.
Metals are considered to be a complete reflector and do not allow any amount of signal to pass through. Materials beneath a metal sheet, fine metal mesh, or pan decking will not be visible.
Radar energy is not emitted from the antenna in a straight line. It is emitted in a cone shape (picture on left). The two-way travel time for energy at the leading edge of the cone is longer than for energy directly beneath the antenna. This is because that leading edge of the cone represents the hypotenuse of a right triangle.
Since it takes longer for that energy to be received, it is recorded farther down in the profile. As the antenna is moved over a target, the distance between the two decreases until the antenna is over the target and increases as the antenna is moved away. It is for this reason that a single target will appear in the data as a hyperbola, or inverted “U.” The target is actually at the peak amplitude of the positive wavelet.
Like any other locating method, its accuracy is based on site conditions and is subject to limitations.
Frequently Asked Questions
It lets us “see” underground without digging. For property buyers and owners, that means locating buried tanks or other objects that could create big problems later.
The equipment sends energy pulses into the ground and measures how they bounce back. Different materials create different reflections, which we interpret on a screen.
Underground storage tanks (both metal and non-metal), utilities, and other buried anomalies that magnetic tools alone might miss.
During tank searches, when planning excavation, or anytime you need reliable information about what is under the surface before you dig or buy.
Yes—dense landscaping, heavy surface clutter, limited access, or certain soil types can reduce clarity. That is why we often combine it with other methods.
Completely non-destructive. Nothing is drilled or excavated during the GPR scan itself.
Knowing what is underground before you commit to a purchase or start construction helps you avoid unexpected costs, delays, and liability.
Tank location is a primary use, but the same technology helps map other subsurface features when needed.
Clear documentation of the areas scanned and any significant findings, explained in practical terms.
We apply GPR as part of a practical locating strategy tailored to the property, then explain the results so you understand what they mean for your decision.
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