Global Positioning System Reference
In-Depth Information
Chapter 7
Sensing Position Without Radio
7.1 Alternatives to Radio Positioning
This chapter discusses all the nonradio methods to find position. Chapter 6
considered radio positioning, which has been the historical method and has many
advantages, especially the ability of radio signals to pass through many materials.
But radio also has some serious disadvantages, which is why it is important to
consider alternative strategies. Sensing is a common thread in this chapter, and it
is important to note that sensors and sensing are a rapidly growing area of both
science and technology. Humans and animals have evolved a keen sense of
position but radio is (as far as we know) never used. All natural positioning is
based on sensing, by which we mean the collection of information from sensors
that convert physical phenomena into information that can be processed.
The main artificial methods align well with nature and include optical
sensing, sound sensing, movement and pressure sensing, and magnetic and
electrical sensing. Nature also uses techniques that technology has yet to master,
for example, using chemical sensing and olfactory sensing and the area of bio-
mimetics (i.e., copying nature) is proving a rich resource for commercial
exploitation.
The great strengths of radio also are associated with its problems, in
particular, the problem of interference. Strict radio regulations limit emissions
(and reception is limited in some instances but mostly from a political
perspective), but these restrictions do not generally apply to the other methods of
positioning. There are health and safety issues but there are no communication
licenses required for the use of, for example, infrared or ultrasonic systems.
Mechanical systems such as odometers, pedometers, accelerometers, and
gyroscopes are obviously not licensed. Many of these technologies have versions
115
 
Search WWH ::




Custom Search