Types of Ground Penetrating Radar

Radar (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 and three dimensional topography imaging).

Impulse Ground Penetrating Radars

• Impulse radars acquire data on the reflected energy as a function of time. It consists of an emitter of high frequency waves in the microwave UHF (ultrahigh frequency) or VHF (very high frequency) band, and a receiver that detects and amplifies the scattered and reflected waves. 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. Impulse ground penetrating radar is broadly used in data collection techniques (whether it is in the time or frequency domain).

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, such as 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 Radar

• A further variation of ground penetrating radar is stepped frequency radar that transmits data on reflected energy in stepped linear increments over fixed bandwidths. These could further be frequency modulated as well. Further, to eliminate the issue of weaker signals from deeper targets getting masked by the stronger signals, compensation is to be made for lateral scattering and taking cognizance of the unambiguous range that can be measured by the stepped frequency radar.

Other Types of Ground Penetrating Radars

• Further variations 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.