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Modem computerised navigation systems on board ships require an accurate log for optimal performance. Traditional electromechanica1logs on board merchant ships have generally been replaced by Doppler logs, which refer the velocity to the sea-bed. However, their operational depth is limited and in deep water the velocity is referred to the water-mass some depth below the hull, where it is influenced by ocean currents. The velocity accuracy ultimately depends on the estimated local sound velocity. The acoustic correlation log has acoustic beams similar to a conventional depth-sounder, with a vertically downward propagation direction and a broad beamwidth. Compared to the Doppler log it is affected less by ship pitch and roll due to its broad beamwidth, and the velocity is virtually independent of the velocity of sound and is referred to the sea-bed to a greater depth. Temporal correlation logs use a two-hydrophone array and the time delay between the two received signals is used to calculate the velocity. The full potential of these logs for world-wide ocean navigation has not been exploited. This thesis investigates the requirements and conditions for temporal correlation logs on board ships to navigate satisfactorily on and off the continental shelf. An experimental temporal correlation log working at high-frequencies with continuous wave propagation is described. It is used to measure the velocity of a tracked platform moving across a water tank and the results are compared to their theoretical values. When fully developed, the log would be suitable for shallow-water operation, and techniques learned can be applied to a low-frequency deep-water correlation log.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 78-80).

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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / There is an increasing demand for practical and powerful navigation system to lead people from one place to another quickly and rightly. The introduction of a new embedded operating system, Windows CE, allows us to design a compact, low-cost, efficient autonomous vehicle location and navigation system. This paper discusses the advantages of Windows CE, demonstrates the possibility of building an AVLNS based on it. Then a realization scheme of hardware platform and navigation software is presented.

The integrated GPS/INS system has become an indispensable tool for providing precise and continuous position, velocity, and attitude information for many positioning and navigation applications. Although the integrated GPS/INS system provides augmented solutions that make use of the complementary features of each component system, its performance is still limited by the quality of GPS measurements, and the geometric strength of the satellite constellation. To address such a problem this research has focussed on the integration of GPS, Pseudolite and INS technologies. The main research contributions are summarised below: (a)A cost effective GPS/INS integration approach has been developed and tested, consisting of a single-frequency L1 GPS receiver and a tactical-grade strapdown INS. Results of field experiments demonstrate that this approach is capable of delivering position accuracies of the order of a few centimetres under a benign operational environment and provides continuously positioning at sub-decimetre accuracy during GPS signal blockage lasting up to about five seconds. (b) A novel kinematic positioning and navigation system based on GPS/Pseudolite/INS integration has been proposed as an alternative to existing GPS/INS systems. With this integration approach, the continuity, integrity, and precision of the GPS/INS system can be significantly improved as the inclusion of pseudolite signals enhances the GPS signal availability and the geometry strength. (c)The impact of pseudolite location errors in such pseudolite-augmented systems has been investigated. Theoretical and numerical analyses reveal that the error effects on measurement models, and on final positioning solutions, can be minimised by selecting optimal pseudolite location(s). (d)A new ambiguity resolution procedure has been developed for use in the proposed GPS/Pseudolite/INS system. It is designed to rapidly and reliably resolve the single-frequency ambiguities due not only to the aiding by pseudolites and INS, but also by adopting a realistic stochastic model and a statistically rigorous ambiguity validation test. The proposed procedure can indeed improve the performance of the single-frequency ambiguity resolution algorithm in terms of both reliability and time-to-fix-ambiguity. (e)An effective cycle slip detection and identification algorithm has been developed, which is suitable for the integrated GPS/Pseudolite/INS system. Test results indicate that induced cycle slips can be reliably detected and instantaneously identified, even if the slips occur at successive epochs. (f)Flight trials have been conducted to evaluate the overall performance for aircraft approach and landing using the GPS/Pseudolite/INS system. Results from these trials show that an enhancement in the accuracy and reliability of the vehicle navigation solution can be achieved with the employment of one or more pseudolite.

Missile navigation systems rely on hybrid INS/GPS systems to employ lower grade inertial sensors for the sake of cost and availability. Current inertial navigation systems on missiles can perform accurately for a limited time without GPS aiding. However, GPS is the most likely system that is going to be jammed in a crisis or war by low cost jammers by any opposing force. Missiles do not have adequate equipment to maintain accuracy when GPS is jammed completely in the battle area. In this thesis, a new method is proposed to improve performance of INS systems onboard missiles and autonomous aerial vehicles with EO sensors in a GPS denied environment. Previously laid ground based beacons are used by the missile EO/IIR seeker for bearing-only measurements and position updates are performed by the use of modified artillery survey algorithms based on triangulation techniques which involve angle measurements. For mission planning, two main problems are identified as deployment problem and path planning problem and a tool for the optimal laying of beacons for a given desired trajectory and optimal path planning for a given network of beacons is developed by using evolutionary algorithms and results for test scenarios are discussed.

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