A probe sensing pad used to detect a position of a probe needle includes a probe area, at least two sensing regions contacting peripheral portions of the probe area, sensing elements of different electrical characteristics connected to corresponding sensing regions, and at least one isolation region for electrically insulting the sensing regions. The reamer includes a carrier frame rotatably coupled to a reaming body, a carrier frame housing slidably coupled to the carrier frame, and an hydraulic cylinder for tilting the carrier frame relative to the carrier frame housing. In one embodiment of the invention, a schema is generated which is utilized to reorder and partition the data into low entropy and high entropy portions which are separately compressed by conventional compression methods.