Design, development and evaluation of an Ada coded INS/GPS open loop Kalman filter

An open-loop Kalman filter capable of processing external measurements that provides an alternate means of upgrading existing INS (inertial navigation system) designs with GPS (global positioning system) equipment has been developed. The open look Kalman filter design is described, with details on mode transition, covariance matching, propagation techniques, and compensation of unmodeled system errors. The filter is able to take over an INS ground alignment, transition to inflight alignment (IFA) mode, process GPS measurements, and compute corrected navigation data. A great advantage of this filter design is its versatility. The filter is not sensor- or system-dependent, and is easily integrated into a mission or central computer. There is added flexibility of easily incorporating other external sensors (e.g., Doppler radar and terrain referenced navigation). Laboratory testing has confirmed proper filter operation and performance on the ground. The inflight alignment modes of operation were evaluated against an INS/GPS simulation developed specifically for the Ada-coded open-loop Kalman filter