The Global Positioning System, used by pedestrians, motorists and truckers the world over is a free application developed and maintained by the US government. The Air Force “develops, maintains, and operates the space and control segments.” As the system of 24 satelites orbits the globe, they transmit signals containing the time and current position. GPS internal standards seek to provide three dimensional location accuracy within a range of 7.8 meters 95% of the time. In practice, users often have positions accurate to within a meter of their actual location.
The accuracy of GPS can be improved by using systems to augment the basic signal provided by the GPS satellites. The Japan Aerospace Exploration Agency (JAXA) has a is developing a project for $1.2 billion called the Quazi-Zenith Satellite System, which will involve 7 satellites orbiting in an asymmetrical figure-8 pattern that narrows over japan and swings down as far as Australia in the Southern Hemisphere. In addition, the system includes 1200 reference stations whose position has been surveyed to great accuracy. Together the satellites and reference stations will be able to correct inaccuracies in the GPS system caused by Japan’s Mountainous terrain and atmospheric interference. The augmented system will provide locations on the centimeter scale which will lead to improved services and new applications of the technology.
The system is constantly improving with a multi-billion dollar budged funded by the Department of Transportation and the Department of Defense. GPS was formerly operated with a Selective Availability (SA) feature engaged which degraded the civilian GPS signal significantly. President Clinton oversaw the Department of Defense turning off this feature at the end of his second term which led to a tenfold increase in civilian accuracy with the GPS system.
As the accuracy of GPS continues to improve, other applications of the technology can develop including autonomous farming, planes that fly on their own and perhaps even vehicles that can drive themselves accurately within current lane widths.