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Advancements in Ubiquitous Location Systems for Precise Contextual Information

Explore the intricacies of location systems for ubiquitous computing, from physical to symbolic, absolute to relative positions, and the integration of diverse location-sensing techniques to enhance accuracy and precision. Learn about current challenges, future prospects, and the concept of ad hoc location sensing to achieve higher levels of location accuracy.

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Advancements in Ubiquitous Location Systems for Precise Contextual Information

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Presentation Transcript

  1. Location System for Ubiquitous Computing Jeffrey Hightower Gaetano Borriello University of Washington

  2. Location • Location is a useful contextual information • Physical versus Symbolic • Absolute versus relative

  3. Location (cont.) • Physical versus Symbolic • Physical : (45。N, 145。W) • Symbolic : in the kitchen, next to a mailbox • Application can determine symbolic location resolution according to the physical location (resolution is important!!)

  4. Location (cont.) • Absolute versus relative • Absolute : shared reference, e.g. latitude • Relative : each object have its own reference or frame • Transfer relative to absolute location • Use triangulation with multiple relative position • Inverse • trivial…

  5. Location System • To locate people, equipment and other tangibles by one or more location-sensing techniques • location-sensing techniques • Triangulation : lateration, angulation • Proximity • Scene analysis

  6. Issue about location system • Accuracy and precision • Accuracy : the grain size of the location system can provide (distance) • Precision : the probability that we can get that accuracy (percentage) • Error distribution along with the density of sensor

  7. Issue about location system • Scale • Evaluate by the coverage area and number of object can locate per unit infrastructure per time interval • Time is a important consideration • Bandwidth • Accuracy

  8. Issue about location system • Limitation • GPS doesn’t work well inside the building • Some tagging systems can read tags properly only when a single tag is present. • Privacy • Cost • Time cost • Space cost • price

  9. A survey of location system • Active badge • Active Bat • Cricket • RADAR • MotionStar magnetic tracker • Easy living • Smart floor • E911 • …

  10. Future work • Lower cost, less amount of infrastructure, better power consumption, etc… • Sensor fusion • Ad hoc location sensing

  11. Sensor fusion • The use of multiple technologies or location systems simultaneously to form hierarchical and overlapping levels of sensing. • Increase accuracy and precision beyond individual system

  12. Ad hoc location sensing • This approach borrows the idea from the ad hoc networking research • Cooperate with other nearby objects by sharing sensor data to factor out overall measurement error.

  13. Ad hoc location sensing • The SpotON system implements ad hoc location sensing • Using low cost tag • Radio signal attenuation to estimate intertag distance • Exploit the density of tags

  14. Q&A

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