|Daniels, Jeffrey - THE OHIO STATE UNIVERSITY|
|Ehsani, Reza - UNIVERSITY OF FLORIDA|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 1, 2008
Publication Date: June 10, 2008
Repository URL: http://hdl.handle.net/10113/20208
Citation: Daniels, J.J., Ehsani, R.M., Allred, B.J. 2008. Ground-penetrating radar methods. In: Allred, B.J., Daniels, J.J., Ehsani, M.R. Handbook of Agricultural Geophysics. Boca Raton, FL: CRC Press. p. 129-145. Technical Abstract: Ground-penetrating radar geophysical methods are finding greater and greater use in agriculture. With the ground-penetrating radar (GPR) method, an electromagnetic radio energy (radar) pulse is directed into the subsurface, followed by measurement of the elapsed time taken by the radar signal as it is travels downwards from the transmitting antenna, partially reflects off a buried feature, and is eventually returned to the surface, where it is picked up by a receiving antenna. Reflections from different depths produce a signal trace, which is a function of radar wave amplitude versus time. Radar waves that travel along direct and refracted paths through both air and ground from the transmitting antenna to the receiving antenna are also included as part of the signal trace. Antenna frequency, soil moisture conditions, clay content, salinity, and the amount of iron oxide present all have a substantial influence on the distance beneath the surface to which the radar signal penetrates. The dielectric constant of a material governs the velocity for the radar signal traveling through that material. Differences in the dielectric constant across a subsurface discontinuity feature control the amount of reflected radar energy, and hence radar wave amplitude, returning to the surface. As an end product, radar signal amplitude data are plotted on depth sections or areal maps to gain insight on below ground conditions or to provide information on the positions and character of subsurface features. This chapter discusses in detail the basic principles, equipment, field procedures, and data analysis/interpretation for ground-penetrating radar methods.