The original Dynamic Cone Penetrometer (DCP) was developed in 1959 by the late Professor George F. Sowers. The DCP uses a 15 lb (6.8 kg) steel mass falling 20 in (50.8 cm) that strikes the anvil to cause penetration of a 1.5 in (3.8 cm) diameter cone (45° vertex angle) that has been seated in the bottom of a hand augered hole. The blows required to drive the embedded cone a depth of 1-3/4 in have been correlated by others to N values derived from the Standard Penetration Test (SPT). Experience has shown that the DCP can be used effectively in augered holes to depths of 15 to 20 ft. (4.6 to 6.1 m).