Application of the digital nautical chart (DNC) database to help identify areas of vertical deflection in the ring laser gyro inertial navigator (AN/WSN-7)

Vertical deflection (VDEF) is a change in the local gravity vector that is sensed by the inertial navigation system (INS) accelerometers. Areas of VDEF are interpreted as erroneous ship acceleration, which result in the propagation of system velocity and position errors. Several manual techniques are identified to assist in minimizing these errors. The primary focus of these techniques centers on changing the ring laser gyro (AN/WSN-7) damping mode at the appropriate time as solely determined by the system operator. By utilizing the vector digital nautical chart (DNC) database, the AN/WSN-7 control display unit (CDU) can provide operator indications when areas of possible deflection are approaching. By automating aspects of determining areas of VDEF, a useful tool is provided to assist the operator in making more informed decisions about changing the damping mode of the AN/WSN-7. The heuristic techniques employed in the AN/WSN-7 navigation operating procedures (NOP) for VDEF operation were encapsulated into an object-oriented paradigm. The VDEF objects and methods are utilized with the geospatial information contained within the DNC database to provide enhanced situational awareness for the AN/WSN-7 operator. The methods of indicating VDEF regions in a semi-automated fashion utilizing the DNC are explained.