Shipborne high-accuracy heading determination method using INS- and GPS-based heading determination system

The heading accuracy of an existing shipborne inertial navigation system (INS) is affected by the oscillatory heading error caused by the misalignment angles between the gyro case and gyro axes. The accuracy of the heading determination system (HDS), which consists of two quadruple GPS antenna arrays, an INS, a total station surveying apparatus (TSSA), and two vessels, is affected by jump errors because of the degradation of tracking performance of the TSSA servo system in high dynamic conditions. Given that only pitch and roll of the INS are utilized in the HDS, we propose a high-accuracy heading determination system that combines the heading rate of the INS and linear fit of the heading difference between INS and HDS, to compensate for jump errors of HDS and oscillatory heading error of the INS. With the designed equipment, both jump errors and the oscillatory heading error can be suppressed effectively. The standard deviations of the heading errors are reduced from ±6 to ±2 and from ±8 to ±5 arcsec in mooring and sea tests, respectively, and a high accuracy of shipborne heading determination can be achieved since the oscillatory heading error is reduced to the 1 arcsec level.