A Brief Description about GPR (Ground Penetrating Radar)
GPR (ground
penetrating radar) is an advanced imaging technology for exploring the
subsurface of the earth. It uses electromagnetic wave propagation to generate
images and identify the changes in the ground's magnetic and electrical
properties. With GPR systems, you can find post tensioning and reinforcing in
concrete, underground utility lines, conduct groundwater studies, and monitor
the structural integrity of aeroplane runways. They may be used to detect land
mines, survey the land for construction, and in forensic research, too.
Standard GPR
equipment is composed of three parts: the control unit, power supply, and the
antenna. It can run on a range of power supply types, such as small rechargeable
batteries to normal 110/120-volt and vehicle batteries. Adapters and connectors
can be used for every type of power source. The control unit houses the
electronics, which supply the radar energy's pulse so the antenna can pick it
up and deliver it to the ground. It contains a computer system and memory for
data storage, too. You can retrieve the data after fieldwork for closer examination.
Some devices come with software for an easier way to transfer or view data in a
computer.
The antenna you use
affects the results of the ground penetrating survey. When the antenna receives
an electrical pulse from the control unit, it amplifies that and transmits it
to the ground at a certain frequency. One of the crucial factors in defining
the depth of penetration is antenna frequency, where the higher the frequency,
the shallower it will penetrate into the ground. However high frequency antenna
may see smaller subsurface elements. Selecting a GPR system requires balancing
penetration depth and detail of the results.
Ground penetrating radar
works by generating a tiny pulse of energy into the material then records
the strength and the time it takes for the reflected signal to return. The
series of pulses in a given area is what is known as a scan. Reflections occur
when the energy pulse goes through the material with a different dielectric
property, generally a change in material. The amplitude or strength of the
reflection is determined by the dielectric constants' contrast and the
conductivities of both materials. Specifically metal elements will return a
strong signal.
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