Try giving Wikipedia a spin:

GPR has many applications in a number of fields. In the Earth sciences it is used to study bedrock, soils, groundwater, and ice. Engineering applications include Nondestructive testing (NDT) of structures and pavements, locating buried structures and utility lines, and studying soils and bedrock. In environmental remediation it is used to define landfills, contaminant plumes, and other remediation sites. In archaeology it is used for mapping archaeological features and cemeteries. It is used in law enforcement for locating clandestine graves and buried evidence. Military uses include detection of mines, unexploded ordnance, and tunnels.

Before 1987 Frankley Reservoir in the UK was leaking 540 litres per second. In that year Ground-penetrating radar was used successfully to isolate the leaks.

Here’s one story I saw online from Australia:
MAJOR Crime police using ground penetrating radar, excavated part of a northern suburbs yard yesterday in their search for a woman missing 17 years.

Helen Joyce Courtney, 33, was last seen on the 20th of September 1991 at her Ingle Farm home. Her disappearance was declared a major crime in 2001.

Mrs Courtney left behind three children, who friends said she was completely devoted to. Her car was found near the Franklin St bus terminal.

Police at the time said her car had been ``meticulously cleaned,’’ which family members had told detectives was not normally in that condition.

Major Crime Detective Inspector Doug Barr said ``their inquiries followed an anomaly identified when ground penetrating radar was used at the Ingle Farm address recently.’’

GPR is used for bridge surveys as well.

grave robbing!

Ground Penitrating Radar is also used to detect tunnels dug mexican drug cartels and smugglers along the U.S. Mexico Border.

Finding my keys?

To detect Secret Underground Lairs.
Muuuaaahaahaa. Muuuuuaahaahaa.

we use it ALL the time at my school to locate burials/mounds/buried structures.

[Note to self: find out what mind-blowingly awesome school @del goes, too. Build time machine and travel back to my teens. Attend said school. Become a superhero.]

hahahaha! Its what you do when you’re ultra involved with the physical anthro program. We have tons of Native American burial sites around here (and more)