Location-based Services Fundamentals and Operation

Chapter 11. Architectures and Protocols for Location Services

A very important subservice needed for building an LBS is the so-called location service (LCS). While an LBS takes location data in order to compile, filter, or select any information or provide any other added value to the user depending on location data, an LCS is primarily concerned with the mere delivery of location data. Compared to position fixes, which only contain a position and perhaps the target's identity or the positioning method used, location data contains additional high-level information that is more appropriate for processing by an LBS application. Usually, location data is composed by a location provider if a location request arrives from a consumer, for example, an LBS provider. This request specifies at least the target location for which the data is needed, the desired format of representation, and the desired quality. In terms of the supply chain introduced in the last chapter, an LCS is based on reference point (b) for controlling positioning and generating location data, as well as on reference points (c) and (d) for making it available to other actors.

The elements of location data can be derived from Table 11.1. Most of them have already been covered in previous chapters. The type of location refers to the up-to-dateness of location data. "Current location" means that the target has been located on request and the delivered location is the most recent one. "Initial location" indicates that the ...