This study presents an evaluation of the accuracy of locations obtained using Assisted GPS (A-GPS), WiFi positioning, and cellular network positioning modes on the 3G iPhone. 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 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 with the 3G iPhone measures as the least predictable and least accurate positioning method. It can sometimes be off be several miles. The above pictures shows from a GIS perspective the positioning and accuracy of each type of GPS tracking. It clearly shows that GPS positioning is the most accurate, however, even still it can be hard to pinpoint the exact location. However, as time goes on, these GPS systems, including cellular positioning, will continue to become more advanced and more accurate.
Zandbergen, P. A. (2009). Accuracy of iPhone locations: A comparison of assisted GPS, WiFi and cellular positioning. Transactions in GIS, 13(s1), 5-25.
I have acted with honesty and integrity in producing this work and am unaware of anyone who has not. - Daniel Buffington