low-cost gps network positioning in urban ?o adicionarem erros à posição do recetor, uma vez que

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  • Low-cost GPS Network Positioning in

    Urban Environment

    David Gabriel Ramos e Castro

    Thesis to obtain the Master of Science Degree in

    Engenharia Electrotcnica e de Computadores

    Supervisors: Prof. Jos Eduardo Charters Ribeiro da Cunha Sanguino

    Prof. Antnio Jos Castelo Branco Rodrigues

    Examination Committee

    Chairperson: Prof. Adolfo da Visitao Tregeira Cartaxo

    Supervisor: Prof. Jos Eduardo Charters Ribeiro da Cunha Sanguino

    Member of the Committee: Prof. Fernando Duarte Nunes

    November 2014

    http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=JO3vuLBqN9NN7M&tbnid=j0w7esXxrErcjM:&ved=0CAUQjRw&url=http://agendatecnica.org/evento/concerto-piano-american-corner/&ei=9JITUrO4B-Kv0QX6i4DYBA&bvm=bv.50952593,d.ZG4&psig=AFQjCNEMsxH6CVsJcH0a6048nOJ7y6zcnQ&ust=1377100906208761
  • iii

    ACKNOWLEDGEMENTS

    This thesis is more than the final research for the conclusion of my degree; it is one of the most

    important milestones of my life.

    I did not get through this road alone, and there were some people that were very important for

    the successful completion of this project.

    Firstly, my acknowledgements are for my family, who has given me sustenance and values

    throughout my entire life; in special, for my father, who has already left this world. I have learned

    a lot from him, and to him I dedicate all my work.

    I would also like to thank my colleagues, who I have met at university and, in particular, to Ins

    Sampaio, Beatriz Fria, Tiago Simo, Leonor Gouveia, Joo Fernandes, Catarina Lus and,

    with special emphasis, to Joo Ribas, whose help and support have made my journey much

    easier.

    To Professor Jos Sanguino, an example of dedication and happiness at work, who has helped

    me not only with this thesis but also with some modules in which he was present.

    To Catarina Rodrigues, who had the patience to stay with me and gave me the support to finish

    my thesis.

    Finally, to Edisoft S. A., a Thales Group Company, that has opened me the door to the

    enterprise world, investing in me and in my education. This is proof that IST is preparing its

    students at the highest level.

    Thank you all

  • iv

    ABSTRACT

    The GPS (Global Positioning System) allows the estimation of the absolute position of a

    receiver, via signals transmitted by satellites. However, this estimation is affected by errors,

    especially those resulting from the atmospheric effects.

    With the goal of minimizing the impact of these errors, it is, therefore, presented an innovative

    solution for the determination of the position of a rover receiver, through its relative positioning

    to a network of three fixed receivers, using double differences algorithms that eliminate major

    errors.

    All the receivers that were used are referred to as low-cost, acquire signals from one single

    frequency, L1, and have the ability to acquire and to lock the phase signal data. The use of

    these receivers was related to the fact that they are the most common in the civil community.

    Therefore, this network can actually be a contribution to the improvement of the receivers'

    position in urban scenario.

    For a better estimation of the rover receiver, it is important that the fixed receivers are known

    with high precision, since the estimation of its position is given by the relative positioning of the

    fixed receivers.

    The tests performed to evaluate the developed and implemented algorithms for this dissertation

    showed that the designed network significantly decreased the existing GPS errors. In this way,

    using only code signal data, the accuracy of the rover receiver's position was increased, in

    comparison with the positions calculated by the stand-alone algorithm.

    The GPS data needed to validate the proposed algorithm in this thesis was obtained using real

    data and tested in MatLab.

    Keywords: Baseline, Code Smooth, Double Differences, Least Square Method, Network

    Algorithm

  • v

    RESUMO

    O sistema de GPS (Global Positioning System) permite a estimao da posio absoluta de um

    recetor, atravs dos sinais emitidos por satlites. Contudo, esta estimao afetada por erros,

    principalmente aqueles que resultam dos efeitos atmosfricos.

    Com o principal objetivo de minimizar o impacto destes erros, apresentada uma soluo

    inovadora para a determinao da posio de um recetor mvel, atravs da sua posio

    relativa a uma rede de trs recetores fixos utilizando algoritmos de diferenas duplas que

    eliminam os principais erros.

    Todos os recetores utilizados so denominados low-cost, adquirem sinais de uma nica

    frequncia, L1, e tm fraca capacidade de aquisio de dados de fase do GPS. A utilizao

    destes recetores prendeu-se com o facto de serem os mais comuns na comunidade civil,

    podendo esta rede ser uma contribuio para a melhoria da estimao da posio de um

    recetor mvel em cenrio urbano.

    Para uma melhor estimao do recetor mvel importante que a rede seja precisa, ou seja,

    que os recetores fixos que a constituem tenham a sua posio muito bem determinada para

    no adicionarem erros posio do recetor, uma vez que se trata de posio relativa.

    Os testes realizados aos algoritmos desenvolvidos e implementados no mbito desta

    dissertao, demonstraram que a rede concebida diminui drasticamente os erros existentes no

    sistema de GPS. Desta forma, aumentou-se a preciso da posio do recetor mvel em

    comparao com as posies estimadas pelo algoritmo stand-alone, utilizando apenas os

    dados do cdigo de GPS.

    Os dados de GPS necessrios para a realizao e verificao dos algoritmos propostos para

    esta tese foram obtidos com recurso a dados reais e testados em MatLab.

    Palavras-chave: Duplas diferenas, Filtragem do cdigo, Vetor distncia, Mtodo dos mnimos

    quadrados, Rede de GPS

  • vi

    ACRONYMS

    bps ......................................................................................................................... Bits Per Second

    C/A ..................................................................................................................... Coarse/Acquisition

    DGPS .................................................................................. Differential Global Positioning System

    DoD .................................................................................................... U.S. Department of Defense

    ECEF ................................................................................................... Earth-Centered Earth-Fixed

    GNSS ....................................................................................... Global Navigation Satellite System

    GPS ....................................................................................................... Global Positioning System

    KF ............................................................................................................................... Kalman Filter

    LoS .............................................................................................................................. Line-of-Sight

    LS ............................................................................................................................. Least Squares

    MCS ............................................................................................................ Master Control Station

    MR ......................................................................................................................... Master Receiver

    NRTK ............................................................................................... Network Real-Time Kinematic

    ppp ............................................................................................................ precise point positioning

    PR ............................................................................................................................. Pseudo-range

    PRN ............................................................................................................... Pseudorandom noise

    RR .......................................................................................................................... Rover Receiver

    RTK ................................................................................................................ Real Time Kinematic

    SA ................................................................................................................................ Stand-Alone

    SV ............................................................................................................................. Space Vehicle

    UERE ................................................................................................. User Equivalent Range Error

    UTM ................................................................................................ Universal Transverse Mercator

    WLS ..........................................................................................................Weighted Least Squares

    SYMBOLS

    c Speed of light

    e Direction cosine

    Error parameter

    Carrier wavelength

    Geometric distance

    Single difference

    Double differences

  • vii

    INDEX

    1 INTRODUCTION .............................................................................