Principles and Simulation of JTIDS Relative Navigation

The time-synchronous operation and high accuracy time-of arrival (TOA) measurement capability of Joint Tactical Information Distribution System (JTIDS) terminals makes possible a high performance relative nagivaton (RELNAV) function through addition of only software in the terminal's computer program. The principles of operation, the basic observation equations, and the system architecture for both absolute (geographic) and relative navigation are described. Sequential passive ranging by means of the TOA measurements, in conjunction with appropriate source selection logic and a recursive (e. g., Kalman) filter mechanization are employed to determine the user's position, velocity, and time bias. The filter algorithms and error sources, the software functional flow, and some simulation results are presented.     

New Developments in Radar and Radio Sensors for Aircraft Navigation

Recent developments in airborne Doppler and ground mapping navigation radars and ground and satellite based radio systems are described. Simultaneous lobing and slope tracking techniques can remove the well-known Doppler sea bias error in fast and slowly moving vehicles. Doppler velocity information can be extracted from coherent forward-looking mapping radars, and high position fixing accuracy can be achieved by synthetic aperture radars. In radio navigation systems, such as Loran, Omega, and satellite systems, direct-ranging and differential techniques greatly reduce the geometric dilution and propagation effects which have plagued conventional radio navigation systems. The advantages gained by mixing of the data from these and other navigation sensors in a digital multisensor system are discussed and approaches for processing these data are suggested.