Automatic Omega Station and LOP (Line of Position) Selection

摘要

Omega is a worldwide navigation system based on 8 VLF transmitting stations dispersed widely around the globe. The phase difference between the signals of any two Omega stations can provide a line of position (LOP) on the earth's surface. Two such LOPs intersect to provide a position fix. Generally several LOPs are selected to improve the accuracy and reliability of the fix either by using a least squares technique or as in MINS (Marine Integrated Navigation System) a more sophisticated Kalman filter technique. The resulting position accuracy and reliability depends on many factors such as geometry and signal strength. This report describes these factors and a set of algorithms used by MINS to automatically select a best choice of 5 Omega stations and 4 LOPs. This includes a modal interference predictor and a multi-LOP geometric dilution of precision calculation.