Ground-penetrating radar, or GPR, is a means of exploring the shallow subsurface with electromagnetic waves (radar), usually in the 10 to 1000 MHz band. The two-way traveltimes of reflected radar waves give the depths where changes in electrical properties occur. Also called georadar, ground probing radar, and surface penetrating radar. See Figure G-9.
FIG. G-9. A ground-penetrating radar record appears similar to a very shallow-penetration seismic section. (From Annan and Gosway, 1992.)