The Global Positioning System (GPS) satellite network provides precise positioning and timing information, free, to all users worldwide. The difference between devices that simply provide GPS positioning data, known as receivers, and full-blown navigation systems that allow you to navigate effectively through the trips you make every day, comes down to the layers of functionality added in navigation systems, allowing you to make more and varied use of the original GPS data.
GPS is a network of satellites in Earth orbit sending out signals, and a ground-based infrastructure to ensure the signals are accurate. Originally designed for the exclusive use of the U.S. military, it has, since May 1, 2000, been freely available for use by everyone, worldwide.
To make use of the GPS signals coming from any of the satellites–30 are in orbit, with at least 24 usually active at any time–you need a GPS receiver. This receiver is a very small, increasingly cheap computer chip, usually surrounded by hardware. All a dedicated GPS receiver actually does is receive the signals–usually from at least four satellites to get a precise location-fix–and relay that information, in the form of coordinates, to a screen.
This is relatively raw data, and it has traditionally needed to be compared with other things, such as a map showing positions in the same coordinate frame. Nevertheless, the comparative precision of location you can get from a GPS receiver, compared to, for instance, dead reckoning, has spurred the growth of GPS as a commercial success.
The Key Difference
GPS receivers are also, in their simple, dedicated form, used a great deal behind the scenes, not for their ability to give precise positioning, but for their ability to give precise timing information. A surprising amount of civilian infrastructure now relies on GPS timing signals, from power grids to mobile and landline phone networks, to the stock exchange.
The key difference though between GPS receivers and a navigation system you can easily and effectively use to get you from one place to another can be expressed in one word: functionality. Knowing your precise coordinates at any point is useful only to a handful of people.
By adding a mapping layer and plotting the GPS data, you have a navigation system that tells you where you are in a way you can use effectively. A database of locations within your area creates a navigation tool to plot and track travel through a typical day. In terms of using GPS in different environments, such as at sea or in the air, adding a layer of information that, for instance, allows you to pre-plot your route turns your raw GPS co-ordinates into a tool for collision avoidance, and in some cases, for compliance with the law (where there is restricted airspace for instance). Adding the facility to make use of an augmentation system (in the US, the universally available Wide Area Augmentation System, or WAAS) makes your navigation system very much more accurate, allowing for other uses, such as lane-specific highway navigation, or sidewalk-specific pedestrian navigation.
Developers are continually striving to add new layers of functionality, developing new navigation systems from what is essentially, at the core, the same GPS data, and a GPS receiver. Augmented reality, for instance, will give you a real-world-real-time view of where you are, but with extra data labels, showing, for example, the nearest fast food restaurant or the nearest movie theater.
Dedicated GPS receivers will also be updated and expanded, as other countries complete their own versions of GPS–Russia's GLONASS constellation of satellites will be delivering worldwide coverage by the end of 2010, Europe's Galileo system is now scheduled to go worldwide in 2014, and China's Beidou-Compass system will follow suit by 2020, and with each system that is completed, GPS receivers–which will then be GPS-GLONASS receivers–and the navigation systems that are built around them, will be able to offer more and more ubiquitous navigation solutions.