The Wide Area Multilateration (WAM) system - as surveillance and identification element in Air Traffic Management - exploits the reception of SSR transponder signals for the determination of the target position and identity. The measurements can be used both in closed form and by iterative algorithms to obtain the estimate of the unknown target position. The location accuracy is affected by errors related to a) the accuracy of time of arrivals measurements and b) the geometric distribution of the ground stations (assuming perfect time synchronization among the receivers and no multipath phenomena). Outside the boundary of the constellation the position error increases rapidly as the range of the target can be very large as compared to the system 'baseline'. A possible approach to prevent this effect is to surround the coverage area (or better, the coverage volume) with ground stations. The principal limitation of this solution is cornplexity: the installation costs, the maintenance efficiency, the management viability, the security aspects. Where terrain characteristics are compatible whit this kind of layout the 3D position performance can be satisfactory. This work aims to propose a solution for mitigating the large vertical errors in the position estimate, The traditional hyperbolic technique (TOA measurements can be upgraded using the measured elevation angle of the target. The elevation angle can be measured by one of the stations equipped with an array processing antenna and related processing means. The elevation angle is a significant information in WAM as in many cases (e.g. flat regions) the receiving stations are at nearly constant height, thereby creating a very limited sensitivity of the system to the variations of the target altitude, i.e. an ill conditioning in the reconstruction ofthe coordinates, In this paper the angle measurement is used in the iterative location algorithm and the results are compared to the iterative case without angle measurements. The purpose is the reduction of the ill-conditioning of the connection matrix due the poor vertical distribution of the sensors. The knowledge of the pair of elevation angles in which the target must lie improves the accuracy of the solution. The performance is compared in terms of the position accuracy, the probability of convergence and the average number of iterations.


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    Title :

    Target location in wide area multilateration using the elevation angle


    Contributors:
    Galati, G. (author) / Magaro, P. (author) / Paciucci, V. (author)


    Publication date :

    2007


    Size :

    12 Seiten, 13 Bilder, 10 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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