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Accuracy of iPhone Locations: A Comparison of Assisted GPS, WiFi, and Cellular Positioning

July 15, 2009

122467470By Paul A Zandbergen
Transactions in GIS, Volume 13 Issue s1, Pages 5 - 25

Abstract: The 3G iPhone was the first consumer device to provide a seamless integration of three positioning technologies: Assisted GPS (A-GPS), WiFi positioning and cellular network positioning. This study presents an evaluation of the accuracy of locations obtained using these three positioning modes on the 3G iPhone. A-GPS locations were validated using surveyed benchmarks and compared to a traditional low-cost GPS receiver running simultaneously. WiFi and cellular positions for indoor locations were validated using high resolution orthophotography. Results indicate that A-GPS locations obtained using the 3G iPhone are much less accurate than those from regular autonomous GPS units (average median error of 8 m for ten 20-minute field tests) but appear sufficient for most Location Based Services (LBS). WiFi locations using the 3G iPhone are much less accurate (median error of 74 m for 58 observations) and fail to meet the published accuracy specifications. Positional errors in WiFi also reveal erratic spatial patterns resulting from the design of the calibration effort underlying the WiFi positioning system. Cellular positioning using the 3G iPhone is the least accurate positioning method (median error of 600 m for 64 observations), consistent with previous studies. Pros and cons of the three positioning technologies are presented in terms of coverage, accuracy and reliability, followed by a discussion of the implications for LBS using the 3G iPhone and similar mobile devices.

9 Comments
  1. John Davies permalink
    July 28, 2010 4:52 am

    Hi, I would be interested in receiving this study in full please.

    Regards

    John

  2. Mark Shkolnikov permalink
    August 17, 2011 10:59 am

    I second Mr. John Davies.

  3. Matt Artz permalink*
    August 17, 2011 11:09 am

    The full paper can be accessed here:

    http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9671.2009.01152.x/full

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