Indoor localization method comparison: Fingerprinting and Trilateration algorithm

Enhanced Positioning Systems (EPS) are able to supplement Global Positioning Systems (GPS) in indoor environments where GPS cannot work because of disrupted or weak signals. Most EPS are Wifi-based because Wifi is a common technology available in many indoor environments and is deployed in cost effective manner. Fingerprinting and Trilateration are the two general methods used for calculating position with Wifi-based EPS. This paper will briefly introduce these two methods, summarize their common ground and differences, and compare the strengths and weaknesses of each. Background and Relevance As GPS becomes a routine tool for navigation and wayfinding more and more mobile handled devices (smartphones and PDAs) are integrating GPS. However, an important and well-known limitation of GPS is that it cannot work inside buildings because of the weak signal’s inability to penetrate building material. EPS is an important supplement for GPS in indoor environments where GPS cannot work. Most EPS are Wifi-based because Wifi is a common and accessible technology that provides the basic information necessary for indoor positioning without requiring additional hardware. In the case of Wifi-based indoor localization, the fingerprinting method based on Wifi singnal strength observations is often employed (Mok & Retscher, 2007). An alternate method is the trilateration algorithm which is also implemented in GPS; trilateration uses distance to surrounding Access Points which, in the case of Wifi routers, is derived from signal strength values.