Navigation

The book intends to provide an encyclopedic view of navigation. It is designed for students, for users interested in the background of navigation, for those who try to enter the complex world of navigation, and also for geodesists going to extend their knowledge towards the real-time applications dominant in navigation. The book does not attempt to discuss all application fields in detail, it is not applicable as a guide for developing navigation systems or tools, and it is not a handbook for practitioners in operating navigational equipment.

Even if the Latin roots of the word “navigation” appear restricted to seafaring, today it implies to move on land, at sea, in the air, or in space. The importance of navigation becomes immediately obvious when reflecting on its need: everybody is concerned. Not only mankind, even animals navigate to reach remote points and to return back to their homes — be it a house, a cavern, or a nest.

In three-dimensional space a triple of coordinates is needed to define the position of a point. Coordinate or reference systems are used for a consistent representation of all spatial points. If points are subject to motion relative to the reference system, then the coordinates are time-dependent. In this case, three-dimensional space is complemented by one-dimensional time.

Electromagnetic waves are formed when an electric field (E-field) couples with a magnetic field (H-field). Field vectors of the electric and the magnetic field of an electromagnetic wave are perpendicular to each other and to the direction of the wave (Fig. 4.1). The plane containing the field vectors of the E-field defines the polarization of the wave (linear, circular, or elliptical).

Since maps are planar representations of parts or all of the earth’s surface, they serve as navigational tools. Navigation consists of positioning and guidance and the use of maps seems to be the missing link Based on a position visualized in the map, guidance depends on map information about the closer or wider surrounding of the position.

Terrestrial navigation cannot be defined in a rigorous manner. The heterogeneous techniques and methods make it difficult to define a unique classification. Throughout this book, the notation terrestrial navigation is applied to all techniques that are based on terrestrial sightings and/or measurements; however, radio navigation systems are not included. Terrestrial navigation comprises dead reckoning, visual navigation, and some other generic position fixing techniques. These methods are applied in land, maritime, and aeronautic applications.

In the early days of marine navigation, stellar constellations have extensively been explored. Examples are found even in mythology like in the epos about the hero Odysseus written by the Greek poet Homer. A description for celestial navigation (or astronomical navigation, also briefly astronavigation) on land is the biblical story of the three Magi following the star of Bethlehem (no matter that the “star” actually was a conjunction of Saturn and Jupiter) to find out the place of birth of Jesus Christ. In addition, it is well known that the North Star (Polaris) has been used over centuries as reference for heading north.

The main objective of terrestrial radio navigation is position fixing. Referring to a transmitter with known position and a rover to be determined, specific navigation systems give information on directions, angles, distances, pseudoranges, and combinations of these types of information. Considering these quantities as measurements, the term line of position (LOP) as explained in Sect. 3.2.2 becomes fundamental. Depending on the LOPs involved, various kinds of position fixing exist, see Figs. 3.7, 3.8, and 3.9 in Sect. 3.2.2.

A short remark on the terminology is given to avoid misinterpretation. “Satellite-based navigation” means navigation based on satellites, i.e., using signals transmitted by satellites. Quite often, this full nomenclature is shortened to the expression “satellite navigation”. This could be misleading because the navigation of satellites could be associated. Primarily, this book implies satellite-based navigation and the authors tried to use the correct denotation. Frequently, the term global navigation satellite system (GNSS) is used to refer to the current global systems.

First development steps towards GNSS augmentation systems are associated with differential GPS (DGPS) positioning. A short introductory review on this process is given.

The origins of inertial navigation date back to the 1920s. During World War II, first operational inertial guidance systems for ballistic missiles were developed in Germany. The first inertial navigation systems (INS) for aircraft use were constructed by Charles S. Draper at the Massachusetts Institute of Technology (MIT) in 1950. The development of specialized systems for inertial surveying started in the 1970s.

Image-based navigation aims at navigating objects by processing series of image data. These image data may be recorded with passive sensors like digital cameras or active instruments like laser scanners. Image-based navigation allows to extend the definition of navigation beyond the so far primarily geometric task. Due to the interaction of the sensor with its surrounding, sophisticated techniques may be developed permitting autonomous vehicles to find their way even within unknown surroundings. Image-based navigation has the potential of complementing traditional tasks of navigation with intelligent problem solutions. Thus, current fields of application often refer to robot technology, covering the operation and control of industrial robot arms up to the guidance of mobile robots. In many of today’s realizations, image-based navigation serves as one component of a multisensor navigation system and is responsible for specialized tasks like collision avoidance.

If a navigation system uses more than one sensor simultaneously, the method is denoted as integrated navigation, and the determination of the state vector (position, velocity, and attitude) of the vehicle has to follow principles of sensor fusion.

According to the basic definition, navigation consists of two fundamental components: positioning and guidance. Thus, many applications within intelligent transportation systems (ITS) are not only based on position determination but are also essentially dealing with problems of vehicle and traffic guidance. This applies to land-based systems and maritime and aeronautic applications as well. Guidance in its turn is very often based on routing problems as the optimal path, the traveling salesman problem (TSP), etc.

The tools of navigation serve a broad spectrum of applications. One of the main topics refers to the wide range of vehicle and traffic management, which is characterized by a high degree of interdisciplinarity. The navigational components are correlated with tools of transportation and traffic sciences, telematics, geoinformatics, and of many other disciplines. Navigation is inherent in any kind of traffic and transportation. For example, questions like “where am I?” and “how to go?” are associated with the main tasks of navigation, namely, positioning and guidance of individual vehicles or a collective of vehicles. In addition, vehicle and traffic management requires an adequate infrastructure for processing and transmitting traffic-related data and information. In this respect, (traffic) telematics contributes essentially to the success of a traffic management system. Covering topics of telecommunications as well as informatics, telematics strongly cooperates with geoinformatics, which mainly focuses on the collection, administration, evaluation, and visualization of geographic data. In connection with traffic telematics, geographical information systems (GIS) handle data and information about vehicles and objects of the traffic infrastructure associated with a position or location on land, at sea, or in the air. Meanwhile, a good deal of the GIS applications cover topics of traffic and transportation.

Land navigation is a task of everyday life of most people, either in terms of finding a way as a pedestrian or when steering a car or other vehicle. This section deals with land vehicles; pedestrian navigation is treated in Sect. 16.2.1. In contrast to marine and aeronautic navigation, characteristic phases of navigation cannot be applied to land transport due to the greater flexibility afforded by land users when assessing their position. Land navigation requirements differ depending on what the user intends to do, the type of transport system used, and the user location (2001 FRS: p. 2-1).

The Latin saying “citius, altius, fortius” meaning “swifter, higher, stronger” is especially applicable in sports. A success of today may be a defeat of tomorrow. The scientific development usually takes a similar course. As seen from the history in Chap. 2, the evolution of navigation from the technological point of view is fully coherent with this Latin phrase, whereas the basic objectives to be fulfilled remained the same over the centuries.