This paper describes a new method of determining the dip and strike of subsurface formations in the earth from measurements taken in a single bore hole. The method is based on the fact that the drilling process erodes some formations more than others. A log is made of three simultaneous profiles of the bore-hole wall which are oriented with respect to compass north. These profiles enable measurements to be made of the vertical displacements of the edges of hard strata protruding into the bore hole. From these measurements and from continuous measurements of inclination and direction, the dip and strike of the subsurface formations can be calculated.

An extensive field-testing program has proved the principles involved to be sound. During this field work, dips ranging from zero to 75° were measured. It was found possible to re-log a given well and reproduce approximately 70 per cent of the final dip results within 2°. From such results it is concluded that the profile method of measuring the dip of subsurface formations is sound and of considerable value in the study of subsurface geology.