Pairs of level sensing devices are used in a method that aligns plane surfaces to one another. One of the pairs of level sensing devices is located on each of the plane surfaces. The level sensing devices of each pair are aligned and positioned parallel to two orthogonal axes of the plane. The output...http://www.google.es/patents/US5031330?utm_source=gb-gplus-sharePatente US5031330 - Electronic boresight
