Africa Surveyors January-February issue 2023 digital

GROUND PENETRATING RADAR
Ground
Penetrating
Radar
Ground Penetrating Radar (GPR) is an electromagnetic
technique that can detect changes in the subsurface
without disturbing the surface. It works at a low
frequency and can reach depths of 30 to 40 meters. The process
is non-destructive, safe, and accurate. It can identify metallic and
non-metallic objects, voids, and other structures. It can also be
used to detect excavations, back-filled areas, and other ground
disturbances.
GPR is most effective in favorable conditions, such as sandy soils,
which allow the transmission of the radar pulse. It is unique in
its ability to detect small objects and determine their depths.
However, it has limitations when used in less-than-ideal conditions.
In particular, fine-grained sediments can scatter the radar signal,
which limits its depth penetration.
The total round-trip time between the antenna and the subsurface
feature is important for determining how far the radar can
penetrate. This time is dependent on the amount of scattering
and EM energy that is released from the target. The amount of
scattering depends on the water content of the subsurface and the
concentration of free ions in the soil. Additionally, heavy vegetation,
water on the surface of the ground, and other factors can affect the
EM wave.
GPR works by sending high-frequency electromagnetic waves through
the subsurface. These waves then reflect back to the receiving antenna.
This process allows GPR to detect changes in the EM properties of
the materials. EM properties vary according to the type of soil or rock
material, bulk density, and water content. An antenna is placed on the
ground surface, and the signals are reflected off the boundary where
there is a difference in EM property.
GPR can penetrate up to 100 feet in some cases. However, its depth is
limited by the conductivity of the material. High-conductivity materials
such as granite and limestone will not absorb the waves as quickly as
lower-conductivity materials do. However, the depth of GPR penetration
can be determined using the information gathered by GPR.
GPR is an effective tool for mapping underground utilities and locating
materials inside concrete. The technology has many applications
in engineering and construction. It can also be used for structural
assessment. For example, it can determine the level of degradation of
concrete in a structure, enabling remediation efforts.
GPR equipment consists of a transmitter and receiver antenna
and a radar control unit. The control unit synchronizes the signals,
controls the transmitter and samples the receiver, and transmits
the signals to a recording or display device. The resulting images
are then processed and interpreted.
Ground Penetrating Radar is an effective and versatile tool for
detecting metallic objects. It works best when targets are made
of high contrast, such as metallic materials. The versatility of
this technique makes it an invaluable tool for a wide variety of
practices. In addition to its effectiveness for detecting underground
structures, it can also be used for archeological research.
A ground-penetrating radar (GPR) mounted to a scanning cart.|image:
MDPI
28 January-February issue l 2023 www.africasurveyorsonline.com