Wifi Positioning
Wifi Positioning was pioneered by a U.S.based firm named Skyhook Wireless in 2007. The system builds a database by passively collecting and integrating uniquely identified wireless hotspots with high-precision location information. This is typically within a dense area such as a city. Skyhook Wireless then leverages this database to provide a coarse-grained location information without requiring dedicated Global Positioning System (GPS) hardware. The system was intended for use by early generation smartphone devices and was a key feature in the deployment of the the first version of the Apple iPhone as a means to preserve battery life while requesting its geographical location. Other terms used to describe this technology are Assisted-GPS or Augmented-GPS (A-GPS). Due to the proliferation of smartphones across the world, many companies including Skyhook, Unwired Labs, and Combain Technologies maintain updated databases of geocoded wifi hotspots across the world at low costs. \cite{wikipedia}
Finally, A significant advantage to using Wifi positioning over GPS is avoiding the Urban Canyon effect that causes GPS systems to malfunction in urban areas with a presence of densely packed skyscrapers.