Ground Penetrating Radar Function

A GPR system is made up of three main components (Figure 1):
  1. Control unit
  2. Antenna
  3. Battery

Figure 1. GPR System

The system is controlled by an attached laptop with proper control software. This system allows data processing and interpretation without having to download radar files into another computer. It allows for quick data evaluation in the field.

GPR operates by sending a little pulse of energy into a material and recording the strength and the travel time of the reflected signal (Figure 2). The antenna receives the electrical pulse produced by the control unit, amplifies it and transmits it into the ground or other medium at a particular frequency. Antenna frequency is one major factor in depth penetration. The higher the frequency of the antenna, the shallower into the ground it penetrates. A higher frequency antenna is required to spot smaller targets. Scan is produced from a series of pulses over a single area. Reflections are produced when the energy pulse enters into a material with different electrical conduction or dielectric permittivity from the material it left. The strength, or amplitude, of the reflection is determined by the contrast in the dielectric constants and conductivities of the two materials. Part of the send energy pulse is reflected back to the antenna when signal passes material with different properties, part of it keeps penetrating further until it either attenuates or the GPR control unit has closed its time window. Various materials depending on their properties can slow down, speed up, attenuate or cause complete reflection of the electromagnetic waves.



Figure 2. GPR Surveying process

Processing
On many occasions the operator will spot the location of the target in the field and the processing can be avoided in case the Client doesn’t require detailed subsurface maps. The location of the target can be simply marked as approximate area on the surface. If detailed subsurface maps are required by the Client processing is necessary.

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