A system and method for determining an orientation of the survey tool within a borehole utilizes a survey tool including a plurality of rotation sensors each having a sensing axis and a direction of least acceleration sensitivity. The plurality of rotation sensors are mounted in a housing with their...http://www.google.de/patents/US7225550?utm_source=gb-gplus-sharePatent US7225550 - System and method for using microgyros to measure the orientation of a survey tool within a borehole
