Methods and apparatus for a tunnel detection system

An instrumented pig, comprising:

• an outer case;
• a rechargeable battery coupled to the outer case;
• an acoustic sub-bottom profiling unit operable to image lithology beneath and around the pig, wherein the ground penetrating radar unit is operably coupled to the rechargeable battery, wherein the acoustic sub-bottom profiling unit comprises a transducer operable to produce an acoustic pulse directed to ground strata and wherein lithological features and voids within the strata create a reflected acoustic pulse, wherein the transducer of the acoustic sub-bottom profiling unit is operable to receive the reflected acoustic pulse;
• and
• a waypoint detector operable to read and receive global positioning system data from an external waypoint.

A method of detecting a subterranean object, the method comprising:

• broadcasting an acoustic signal from an acoustic sub-bottom profiler contained within an instrumented pig, the instrumented pig traveling within a pipeline;
• receiving, at a receiver within the acoustic sub-bottom profiler a reflected acoustic signal;
• receiving, at a signal processor, the reflected acoustic signal;
• processing, at the signal processor, the reflected acoustic signal;
• receiving from a preprogrammed magnetic encoded waypoint, at a waypoint detector, a location data;
• receiving, at the signal processor, the location data;
• and
• geocoding a processed lithology data with the location data.