Gyroscopes; Seismographs; Azimuth instruments; Compasses for measuring; Directional compasses; Electric coils; Electric navigational instruments; Electric sensors; Electrical transducers; Electro-optic transducers; Electronic coils; Global positioning system (GPS); Magnetic and electromagnetic coils; Marine depth finders; Measuring apparatus, namely, angle finders; Navigational instruments for vehicles; Optical sensors; Photoelectric sensors; Satellite-aided navigation systems; Tachometers; P...