Improved heading using dual speed sensors for angular rate and odometry in land navigation

Two radar ground speed sensors are used in a land navigation system to provide improved heading by dampening erratic headings and removing misalignments associated with magnetic compasses. Radar ground speed sensors provide vehicle speed without contacting the ground surface and are not subject to errors such as wheel slippage normally associated with wheel encoders or odometers. Differences between the speed sensors provide a measure of angular rate which is input, along with magnetic compass heading, into a heading pre-filter. This provides an intermediate heading improvement by dampening the erratic magnetic compass heading outputs. The average of the speed sensors provide a measure of distance traveled over a sample interval. Distance traveled and the heading pre-filter's output, are used to establish a dead-reckoning navigation solution. This navigation solution is used as a reference state trajectory in a navigation Kalman filter algorithm, processing differential GPS positions as observations, to estimate position, odometer scale factor, and heading misalignment errors. The heading misalignment estimate is added to the heading pre-filter's heading estimate to provide the final heading improvement for an operator or vehicle guidance algorithm.