From Minitrack to NAVSTAR: The early development of the global positioning system, 1955–1975
The paper outlines the early days of satellite navigation, focusing on the work of the Naval Research Laboratory (NRL) on systems that contributed to the later Global Positioning System (GPS). NRL's innovations included the Minitrack system for space surveillance, the development of high-precision timing systems for use in space, the Timation navigation satellite program, and the first two Navigation Technology Satellites (NTS-1 and NTS-2). NAVSTAR-GPS emerged as a joint Department of Defense (DoD) program in 1973, by which time much of the GPS concept had been developed and a number of GPS technologies had been tested.
Track Optimization Algorithm for Automotive Telematics System
GPS track accuracy forms the building block of automotivetelematics systems. To enhancetrack accuracy more track points are required constraining bandwidth and data storage. This paper presents a GPS track optimizationalgorithm improving GPS track accuracy while maintaining low track point’s count. The algorithm employs a three-step approach;wild-point reckoning, adaptive Kalman filter, and adaptive track-point reduction.Wild-point reckoning method truncates huge deviation in geo-points. Adaptive Kalman filter further reduceserror covariance within GPS data.Track-point reductionoptimize tracking points in GPS data, based on two variables distance and angle, between trackpoints. The algorithm is adaptive to vehicle speed and precision of the GPS receiver to making it universal applicable.The algorithm enhances the efficiency of tracking/telematics system and simultaneouslyreducingDB requirement.The algorithm is a part of the device firmware of Secure Automotive Telematics System (SATS).
The role of time/frequency in navy navigation satellites
This paper discusses the role of time and frequency in three areas: 2) the operational Navy Navigation Satellite System, NNSS; 2) an experimental low-altitude navigation concept termed TIMATION; 3) proposals for advanced navigation satellites. These operating, experimental, and proposed systems all use concepts which allow the user to remain passive. The operational NNSS system uses the Doppler technique to establish user positions to ~100 m. In this concept, the frequencies received from the satellite are compared to the frequencies generated in the user equipment. One can also compare the time a signal arrives from a satellite clock to a time generated in the user equipment clock for passive ranging. The paper shows that this passive ranging problem is easily transformed to the celestial navigation problem. Extension of these techniques allows one to use satellites as clock transporters and hence to compare clocks located throughout the globe to 0.5 µs. Experimental results are shown. It has been possible to determine the effects of radiation on quartz crystals and to determine that this effect is due principally to protons. System concepts are described which show this clock/time technique can determine user position, velocity, and time continuously, accurately, and globally.