| Introduction | | | | single estimate for position, time, and velocity. |
| Satellite navigation isn't rocket science once you | | | | Three and four satellites are the minimum needed |
| know how. Satellite Navigation was originally | | | | to determine positions on the surface of the |
| designed for military applications. The first satellite | | | | Earth and above it. This is done from a global |
| navigation system was Transit, a system | | | | network of reference stations on the ground, |
| deployed by the US military in the 1960s. For | | | | whose positions are known to within centimetres. |
| these reasons, a satellite navigation system is an | | | | The best known is called differential satellite |
| essential asset for any aspiring military power. | | | | navigation, which uses a fixed receiver in a known |
| However due to the growing use of satellite | | | | position as a reference. GPS receivers, which use |
| navigation e.g. marine use, engineering use and the | | | | differential GPS, can have an accuracy error of |
| ever growing in car sat use the growth of satellite | | | | less than 1 metre and even down to a few |
| navigation for everyday applications is set to | | | | centimetres. This type of receiver is now |
| continue. | | | | commonly used in many civil engineering works. |
| Accuracy | | | | How the public benefit from satellite navigation |
| In general, the more satellites used the greater | | | | (Sat nav) |
| the positioning accuracy. Numerous errors can | | | | The explosion of sat nav usage is due to the low |
| degrade the accuracy of a positioning. Therefore, | | | | sat nav costs and how practical they are, |
| the accuracy of the navigation solution depends | | | | especially if you are driving alone and you have no |
| on how the receiver compensates for the | | | | one to help map read. With more and more |
| different error sources. This is largely dependent | | | | motorists venturing abroad in their cars the sat |
| on how the manufacturers of satellite navigation | | | | nav is an indispensable device to help them |
| systems implement the relevant decoding on their | | | | navigate around foreign countries. The latest sat |
| receivers. Most publicly available receivers have an | | | | nav systems also incorporate Traffic Congestion |
| accuracy if about 5-10 metres. However in built up | | | | warnings and then work out an alternative route, |
| areas where the signals from the satellites can be | | | | with voice instructions, to help avoid a lengthy |
| corrupted the accuracy can be a little worse. | | | | delay in traffic. |
| Given the military put the system in place you | | | | Conclusion |
| can be their accuracy will be a lot better than that | | | | Satellite navigation is increasingly becoming a vital |
| seen by the public. | | | | component of aircraft, ships and cars and Europe |
| Position | | | | is concerned about relying entirely on the US |
| Satellite navigation receivers reduce errors by | | | | system. The clearest of these is the fact that |
| using combinations of signals from multiple | | | | satellite navigation will become a fully redundant |
| satellites and multiple correlators, and then using | | | | service for civil aviation users in the event of a |
| techniques such as Kalman filtering to combine the | | | | satellite or system failure. |
| noisy, partial, and constantly changing data into a | | | | |