Types of Ground Penetrating Radars
Radar (abbreviation for ‘Radio Detection and Ranging’) is an electronic instrument that detects mobile and stationery objects by measuring their speed, direction and altitude. Radars are used for a variety of purposes such as air traffic control, speeding traffic and meteorological measurements. Further, a system that images the sub-surface in a non-destructive and non-intrusive manner is known as the ground penetrating radar. It can measure and map a variety of terrain (such as rocks, soil, water, ice, and man made constructions) and is used in different applications (such as archeological surveys, natural resource exploration, civil engineering, forensic investigations, environmental remediation and three dimensional topography imaging).
Types
of Ground Penetrating Radars
Ground penetrating radars consist of an
emitter of high frequency waves in the microwave UHF or VHF band, and a
receiver that detects and amplifies the scattered and reflected waves. Ground
penetrating radars can be of various types; differing primarily in data
collection techniques used (i.e.; whether it is in the time or frequency
domain). These can therefore be broadly classified on the basis of whether they
deploy impulse (called impulse radar; operating in the time domain) or continuous
waves (called continuous wave radar; operating in the frequency domain), and variations
thereof.
Impulse (Ground Penetrating) Radars
Impulse radars acquire data on the
reflected energy as a function of time. Since impulse radar has low cost parts
and deploys simple impulse waveform generating, it is commercially very
powerful. It however has one major disadvantage in that the resolution of its
imaging is restricted by the width of the pulse that is used.
Continuous Wave (Ground
Penetrating) Radars
Continuous wave radars acquire and
continuously transmit data on the reflected energy as a function of frequency. Technique
involved is to transmit a frequency sweep over a fixed bandwidth, i.e. from a
beginning to an end frequency. Reflections waves are mapped as a function of
frequency and are a measure of the energy that has been scattered from
subsurface objects.
Stepped Frequency (Ground
Penetrating) Radars
Another variation is the stepped
frequency radar, which transmits data on reflected energy in stepped linear
increments over fixed bandwidths. To eliminate the issue of weaker signals from
deeper targets getting masked by the stronger signals, compensation is made for
lateral scattering and by taking cognizance of the unambiguous range that can
be most accurately measured by the stepped frequency radar.
Other Types of Ground Penetrating
Radars
Further variations of the above types of
ground penetration radars are ultra wide band radars, synthetic aperture
radars, noise source radars and arbitrary waveform radars. Some custom ground
penetration radars may also be designed, such as borehole radars.
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