This chapter adds an in-depth description of location context, because location is the most prominent context property and the associated tracking technology is increasingly deployed in industry. First, we motivate a number of application areas for this technology in industry, healthcare, tourism, and more. We first describe the different physical properties location sensors can measure and then the principles and algorithms to calculate the locations of mobile entities based on this sensor data. Several commercial location systems and research prototypes are described as implementation examples. Finally, with the help of location models, the raw location information is processed to derive higher-level information meaningful to application services.