Efficient Hemisphere Unambiguous Magnetic Positioning for Helmet Mounted Sights

Helmet Mounted Sights (HMSs) become the important facilities to the cockpits of modern fighter aircraft. The HMSs based on the electromagnetic (EM) positioning have obviously advantages in no Line of Sight (LOS) occlusion, no Infrared Ray (IR) or thermal limitation, and no measure drifting. However, the application of EM HMSs is severely restricted by an inherent hemisphere ambiguity. A method to solve the inherent hemisphere ambiguity of electromagnetic positioning with single 3-axis magnetic source and single 3-axis magnetic sensor is proposed in this paper. The ambiguity is discriminated effectively to enlarge the positioning range of electromagnetic HMSs based on minimum Euclidean distance. Compared with traditional methods, it has significant advantages in positioning accuracy, real-time tracking and handling large-angle errors.