Dear Dennis...
EN-Genius Network's Dennis Feucht answers your design
queries in his new Circuit Design Clinic!
March, 2010
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EN-Genius Network presents a new, interactive
analog design service to readers! Send us your design questions (with
relevant data; schematics in JPEG or GIF, please) for some free
engineering advice from EN-Genius Network's circuit
consultant, Dennis Feucht, on how you might solve a design problem or
improve circuit performance. Submissions may be edited for clarity or
brevity, and submitters and their email addresses will remain anonymous
(unless otherwise indicated). Please send your questions to Dennis here.
Position Location Techniques and Applications
by Dennis L Feucht
by David Muñoz, et al, Published by Academic Press
ISBN 13: 978-0-12-374353-4, hardback, 275 pp, $119.95, 2009
Upon first seeing the title of this book, the question that came to mind was: isn’t “Position Location” redundant? To locate is to identify where something is and for this book, what is being located is position. If you surmise that this book is about the application of GPS, you’re right, but it is more. It is solidly in the category of communications electronics. Position references began as adopted landmarks in ancient times: ziggurats in Sumeria, the lighthouses of Alexandria, Egypt, and the latitude-longitude system worked out by Eratosthenes. The Greenwich meridian, equatorial circle and mean sea level are contemporary landmarks for specifying unique locations on earth. Particular systems use beacons: signal sources of known location. Add to this the accurate measurement of time and several location techniques emerge that use ranging based on time of arrival of a signal, or its difference between signals, or angle of signal arrival, or relative signal strength. This book is constrained to radio-supported localization. GPS reception is an example of a system that does not rely on remote processing to determine location but can determine it own location from signals received from multiple satellites.
Some of the engineering factors in building such a system are the error in locating the landmarks and electronic measurement errors. GPS is limited to satellite line-of-sight locations which exclude indoors and in urban areas with large buildings or natural signal obstructions. Signal processing techniques are applied to increase position resolution. In addition to satellite-based position location, cell phones can also be located through various means and then tracked.
Chapter two dives into the engineering of angle-of-arrival measurement using linear arrays. This kind of theory could be useful for medical instrument developers or in mobile robotics, with coverage of various estimation and cross-correlation algorithms. Chapter three addresses multilateration: the generalization of n observations. For three, it is triangulation. Various methods involving both angle and time measurements are presented, including statistics. Then the more complicated multi-hop case is addressed. Finally, dead reckoning is included, where segments of distance are added.
Chapter four moves into heuristic methods of position location beginning with cell phones. Much attention is given to multi-hop scenarios. The subsequent chapter extends to reconfigurable networks. The book winds down with a discussion of applications. Chapter seven gets back to satellite positioning, with just enough celestial mechanics to attract the attention of the astrionically-inclined.
Overall, this book has a wider potential audience than communications engineers. Anyone involved in scanners, such as medical ultrasound instruments or robotic world-map builders for autonomous mobile vehicles, will have a possible interest in this book because the authors present their material in tutorial form, making it possible to benefit from the basic principles without being a communications specialist. It is also a potentially useful book for social dissidents who are interested in defeating or neutralizing Big Brother technology in a police state, including engineers who seek privacy from government or commercial snooping. Some familiarity with stochastic processes in electronics aids in comprehending book content, though one need not be an expert in signal estimation to benefit from the concepts presented in this book.
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