Abstract: A method and apparatus for directional drilling using mechanical wave detectors and a drill string having a drill bit at a drill bit end of the drill string. During an underground drilling operation in an underground formation, a mechanical wave signal is transmitted using a mechanical wave transmitter carried at the drill bit end of the drill string. The mechanical wave signal is received by an array of mechanical wave receivers at a ground surface above the underground formation. The received mechanical wave signals are processed to determine at least the location of the drill bit in the underground formation. The position and direction of travel data is communicated to a drilling control unit.