290 Personal Content Experience: Managing Digital Life in the Mobile Age applications and services can be designed and deployed, including tagging, information services, and games. In this section, we will look at location-based applications from the personal content point of view. This approach provides us with two options: either the location information is considered personal content as such – that is, all GEMS actions can be potentially applied to loca- tion information directly – or, alternatively, location information is considered a part of the context (that is, metadata), be it the user context or the fi le context, and is primarily used to enhance other types of personal content. Nevertheless, location information is in many cases a major building block of mobile personal content experience. Put simply, a location-based application knows its current location, and can adapt to it. A location-based application can also be referred to as a location-aware application. The most common positioning service to date is the satellite-based Global Positioning System (GPS) (Getting 1993). The position can be acquired with a GPS receiver. The accuracy of a GPS service is usually within a few metres, but with differential correction it can be brought down to a few dozen centimetres. GPS is governed by the US military; Russia also has their equivalent system in place, GLONASS, while the EU is planning to launch a similar satellite-based positioning system, called Galileo. In addition to GPS, there are other positioning services available. As an example, the current cellular network is capable of determining the location of a connected mobile phone. There are various tech- niques to obtain the location coordinates but, regardless of the tech- nique used, the positioning accuracy is much lower than with GPS. The accuracy depends on the technique used, as well as on the cell size, and is typically hundreds of metres. Similarly, wireless local area networks (WLANs) can be used to triangulate the user’s current loca- 6 tion; if the location of the WLAN access points is known, the location of the device can also be determined. 7.2.1 Point of Interest A central concept and an explicit content type related to location- aware applications is a Point of Interest (POI). A POI is defi ned as an “important, distinctive environmental feature”. The term landmark is often used interchangeably. However, in the context of personal content, the defi nition of a POI can be broader – a POI can be a loca- 6 Which is rare at the moment. Building a WLAN-based navigation system requires initial measurement of the location.