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Bohling, Geoffrey C. / A ground penetrating radar study of water table elevation in a portion of Wisconsin's central sand plain
[DNR-050] (1988)

III. Radar theory and hydrogeological applications,   pp. 19-32 PDF (3.7 MB)


Page 19

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III. RADAR THEORY AND HYDROGEOLOGICAL APPLICATIONS
A. Introduction
The aspects of radar theory and performance considerations which
must be taken into account when applying GPR to groundwater studies
are presented in this chapter. The most important factors affecting results
of GPR surveys of the water table are the propagation velocity, attenua-
tion and resolution of the radar signal in the subsurface materials and the
strength of the water table as a reflector of electromagnetic energy. All of
these factors are influenced by the characteristics of the initial radar pulse
and by the electromagnetic properties of the subsurface materials.
Because the radar signal is composed of many different frequencies of elec-
tromagnetic energy and because the electromagnetic properties of earth
materials are frequency-dependent, the analysis of radar signal propagation
is, in general, complex. However, in the range of frequencies employed by
commercially available GPR units (about 1 to 1000 MHz) simplifying
assumptions can be applied to this analysis. These assumptions are
employed in the following discussion. For discussion of the more detailed
aspects of radar signal propagation, see King and Smith (1981) and Ulrik-
sen (1982). The notation used in the following discussion follows that used
by King and Smith (1981).
The specifications of the equipment used in this study and other


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