This blog article discusses the accuracy of GPS Location findings on the Apple iPhone 3G back in 2009 when Apple introduced their GPS tracking Maps.
This article is from a while ago, however, I think it proves a point to how fast technology can change, improve, and strengthen. This article shows that Apple devices did not do so well compared to actual GPS location products on the market at the time.
This picture shows the error created from iPhones using their GPS tracking services back in 2009. Their accuracy was far less than the standard GPS Products.
The cells location was based on their WiFi signal and the study included that the distance from cell towers and the fact that only one metropolitan area was tested could've changed results.
Also, the study states that the WiFi location accuracy was much better indoors compared to outdoors. I think this information is interesting to look at and study and wonder how trusted these WiFi locations were in 2009. Were GIS professionals worried this would lessen their field or create less demand for their work because our phones could perform the same tasks from us walking around, that is what I wondered reading this.
Zandbergen, P. A. (2009). Accuracy of iPhone locations: A comparison of assisted GPS, WiFi and cellular positioning. Transactions in GIS, 13(s1), 5-25.