@techreport{newman2003ubitrack,
        TITLE =  {Fundamentals of Ubiquitous Tracking for Augmented Reality},
        AUTHOR = {Joseph Newman and Martin Wagner and Thomas Pintaric and Asa MacWilliams and Martin Bauer and Gudrun Klinker and Dieter Schmalstieg},
        YEAR =   2003,
        month =   dec,
        NUMBER = {TR-188-2-2003-34},
        url =     {http://www.ims.tuwien.ac.at/publication_detail.php?ims_id=TR-188-2-2003-34},
        pdf =      {http://www.ims.tuwien.ac.at/media/documents/publications/ubitrack.pdf},
        INSTITUTION = {Vienna University of Technology},
        ABSTRACTURL = {http://www.ims.tuwien.ac.at/publication_detail.php?ims_id=TR-188-2-2003-34},
        ABSTRACT = {To enable rich and meaningful Augmented Reality (AR)
                  experiences within a Ubiquitous Computing
                  environment, a detailed, coherent and up-to-date
                  spatial model of the world is essential. However,
                  current tracking technologies are limited in their
                  range and operating environments. This has, so far,
                  restricted the development of wide-area AR
                  applications. To extend the range of AR
                  applications, it will be necessary to combine widely
                  different tracking technologies dynamically,
                  aggregating their data and balancing their
                  trade-offs. In this paper, we propose a formal
                  framework, called Ubiquitous Tracking, which uses a
                  graph-based model of spatial relationships to build
                  dynamically extendible networks of trackers suitable
                  for the high-precision, low-latency requirements of
                  Augmented Reality. The framework is powerful,
                  allowing us to model existing complex tracking
                  setups; extensible, accommodating new trackers,
                  filtering schemes and optimisation criteria; and
                  efficient, allowing an effective implementation
                  within existing AR systems.}
}