Williams, "A Comparison of Circular Error Probable
Estimators for Small Samples," DTIC Document, 1997.
The reality of the air war over Germany--overcast skies, smoke from factories, German antiaircraft defenses, and a myriad of other factors--produced an average circular error probable
of about half a mile (that is, half of the bombs dropped fell inside a circle a half of a mile in diameter, and the other half fell outside) with many bombs hitting the ground up to five miles from the designated target.
With a circular error probable
(CEP) of two miles, it was intended for strategic targets such as cities rather than those requiring pin-point accuracy.
The military tends to define missile accuracy and reliability with a two-dimensional statistical metric called Circular Error Probable
TLE and WDE can be stated as circular error probable
(CEP), as the story explains, which is a 50th percentile measurement.
Its circular error probable
(Cep) of less than 20 metres is achieved by means of an Interstate Electronics GPS receiver with high anti-jam performance, permitting the use of a low-cost IMU (inertial measurement unit).