Positioning is a process to obtain the spatial position of a target. There are various methods to do so, which differ from each other in a number of parameters such as quality, overhead, and so on. In general, positioning is determined by the following elements:

• one or several parameters observed by measurement methods,
• a positioning method for position calculation,
• a descriptive or spatial reference system,
• an infrastructure, and
• protocols for coordinating the positioning process.

The core function of any positioning is the measurement of one or several observables, for example, angles, ranges, range differences, or velocity. Such an observable usually reflects the spatial relation of a target relative to a single or a number of fixed points in the surrounding environment, where a fixed point denotes a point of well-known coordinates. They are often measured by utilizing the physical fundamentals of radio, infrared or ultrasound signals, such as their velocity or attenuation. These signals when used for positioning measurements are also referred to as pilot signals or simply pilots. Furthermore, measurements are sometimes classified into radiolocation and non radiolocation methods. In the former category, observables are directly or indirectly measured by radio signals, while the latter category falls back on other physical quantities, for example, of optical or acoustic nature.

After the required observables have been determined, the target’s position must be derived after taking into consideration the measurement results and the coordinates of the fixed points. This determination is usually based on a certain method that strongly depends on the types of observables used. Examples are circular and hyperbolic lateration or angulation. Table 6.1 shows an overview of the basic positioning methods derived from (Hightower and Borriello 2001) and the associated observables and measurement methods.

Contents

• Classification of Positioning Infrastructures
  • Integrated and Stand-alone Infrastructures
  • Network and Terminal-based Positioning
  • Satellites, Cellular, and Indoor Infrastructures
• Basic Positioning Methods
  • Proximity Sensing
  • Lateration
  • Angualtion
  • Dead Reckoning
  • Pattern Matching
  • Hybrid Approaches
• Range Measurements
  • Time Measurements
  • Received Signal Strength
• Accuracy and Precision
• Error Sources
• Conclusion