Читать книгу Position, Navigation, and Timing Technologies in the 21st Century - Группа авторов - Страница 14

John F. Raquet

Integrated Solutions for Systems, United States

There is little doubt that global navigation satellite systems (GNSS) have changed the way that we think about and use navigation systems. Prior to GPS and other GNSSs, the use of systems which could automatically (without human intervention) determine their own position was generally limited to large, expensive platforms such as aircraft or ships, and even these types of vehicles often required human navigators to assist in the task of navigation. This has all changed with the advent of GNSS, however.

Thanks to GNSS, most people have now become accustomed to their smartphone or vehicle knowing exactly where it is as a part of their everyday lives, and this capability has been built into our expectations. Just as we expect the lights to come on when we turn on a light switch, we also expect a GNSS position fix whenever we turn on a smartphone or other navigation device. This reliance on GNSS goes well beyond obvious navigation devices – we very much depend on many systems which heavily use GNSS for timing purposes, such as banking, communications, and our power grid.

Some have said that navigation is addictive – no matter how much accuracy or availability you have, you always want more. The extreme success of GNSS has, ironically, led to a desire to complement GNSS with other types of sensors for situations in which GNSS is not available, in order to guarantee (as much as is possible) the ability to determine time or position.

Volume 2 focuses in on many of these complementary navigation systems and methods and how they are integrated together to obtain the desired performance. Before diving into the details, it can be helpful to step back and look at the big picture of what is really happening within navigation systems, in order to better understand how the various approaches relate to each other. To do this, it is helpful to develop a “navigation framework.”