Location-based Services Fundamentals and Operation

Chapter 2. What is Location?

When dealing with LBSs it is first important to be clear about the meaning of the term "location". Although most people would claim that they are very familiar with the concept of location, as it, besides time, is one of the major quantities determining our everyday life, it is useful to have a closer look at it and to distinguish between different categories of location information. This chapter provides an overview of these categories. The main focus is on the concept of spatial locations that appear to the developers and users of LBSs in the form of coordinates. This chapter introduces the different ways to express a spatial location in a coordinate system and explains the idea behind datums, which are used for modeling the surface of the Earth. Furthermore, an introduction to the fundamentals of map projections is given, which are needed for projecting the bended surface of the Earth on a planar map.

Location Categories

Basically, the term "location" is associated with a certain place in the real world. When people make appointments, they usually agree to meet at a certain place, such as the airport, a bar, or the office. In other cases, they must inform the place of their residence, for example, in order to receive written correspondence or official directives. What these examples have in common is that location denotes a place of an object of the real world, and hence these kinds of locations belong to the class of physical locations.

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