The invention provides a fast, computationally inexpensive, and highly accurate method and apparatus for edge detection in a digital image, even for edges that are not substantially parallel to the axes of the pixel grid, by exploiting computationally inexpensive estimates of gradient magnitude and direction. A server interface configuration file is used which describes a server interface configuration comprises declarative definitions of data attributes, format information, and a data pool. The axial thrust is controlled, whilst the head and rotor are tilting, hydraulically by counter-pressure, ensuring they do not surpass the power collected and the moments on the structure, shoe and ground. The housing protecting the sensing mechanism from downhole conditions. In a case where the shoe wears down, only the shoe is replaced. A time measurement circuit determines a time interval between the arrival of a trigger signal and a subsequent cycle of the DDS clock, which time interval is used to either adjust an initial phase accumulator value or delay the DDS clock so that a constant time is maintained between the arrival of the trigger signal and the desired output signal.