User's Manual

GPR4 Utility Scanner

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User Manual

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Earth Science Systems, LLC

October

2019

Page 20 of 27

5.8 System Care, and Cleaning

The pavement density system kept clean and free of debris. The sensor unit can be

cleaned with water and a mild detergent.

6 Theory

6.1 Theory of Operation

The Utility Scanner uses ground penetrating radar (GPR) to characterize the surface

beneath the sensing unit. The GPR sends a low-energy impulse of electromagnetic (EM)

energy towards the surface. Some of this energy penetrates into the subsurface and some is

reflected back towards the sensor unit. The amount of reflected energy depends on the

contrast in dielectric constant and electrical conductivity of the soil and embedded objects. By

measuring the travel time of these waves, the depth to the reflectors can be determined in a

manner analogous to a fish finder. By moving the scanner over the surface and detecting object

beneath it, a 2D or 3D cross section of the subsurface can be obtained.

High frequency radar waves (i.e. 750 MHz) provide better spatial resolution than lower

frequency radar waves, but they attenuate quickly as the travel through the subsurface.

Subsequently they cannot detect objects deeper than about two feet. Lower frequency radar

waves (i.e. 350 MHz) are able to penetrate more deeply (to about 20 feet) but do not provide as

much detail in the subsurface images.