string above the bit the borehole 3 is drilled downward from the surface and then caused to turn toward a horizontal condition as shown when the depth of the shale seam is reached that may be nominally horizontal but there may be a known or approximately known small inclination angle to the seam the object of the drilling process is to drill for an extended distance while maintaining such drilling within the shale seam to provide a path for enhancement of fracking equipment and or the recovery of hydrocarbon such as oil or gas from the selected seam previously little information was available to assist in maintaining the drill bit path within the seam as during horizontal drilling to different locations within the seam gamma ray detectors either total gamma ray counters or so called focused gamma ray counters were frequently used for detecting an out of coal seam drilling condition such detectors provide very short depth of investigation and are located a considerable distance behind the bit so that the resulting borehole path tended to have considerable up and down bending deviation since the bit had to be out or nearly out of the bed or formation layer before deviation from the desired trajectory was sensed and only then could a correction in drilling direction be made using known measure while drilling techniques to change the inclination of the.