Directly or indirectly everyone is connected with GPS technology. They are found in your mobile phone, automobiles, almost everywhere. You cannot hide from this tiny device.
Decades of engineering went on to improve its accuracy. The use and work of GPS technology are truly amazing.
During the course of this work, we have revealed the mystery about GPS accuracy. Here you have some of the useful facts that we have discovered.
What do you understand by the term GPS?
GPS or Global Positioning Service is a space-based satellite navigation system that provides users with tracking, timing, and navigation service in all sort of weather, from anywhere on earth or near to it.
This positioning service is made up of a network of 24 satellites which is placed into orbit by U.S. Department of Defense. It was initially projected for military purpose, but in the year 1983, United States government made this technology available for civilian use. It works 24 hours a day and in any weather condition from anywhere in the world. It is completely free no subscription or set up fee is required to use it.
History of the most popular technology tool – GPS
The Global Positioning System (GPS) network that we all use today is called Navstar and is operated by US Department of Defence (DoD). Currently, this Global Navigation Satellite System (GNSS) is the only fully operational system however, China has COMPASS, Russia has GLONASS, and the EU has GALILEO, each is at its development or testing stage.
On February 22, 1978, Navstar was originally designed and reserved for sole military use, but the civilian was allowed to use it in later 1983. For civilian use, the GPS tracker accuracy was purposely degraded to +/- 100m using Selective Availability (SA) system but in May 2000 it was eliminated.
Know how Global Positioning System Works?
There is no easy way to explain how GPS works – it’s network satellites that orbit the earth at an altitude of 20,000 km. No matter where you are in the world, at least 4 GPS satellite is visible all the time and each transmits the data about its position. The three vital parts of GPS are satellite, control station and receiver.
- GPS receiver (your device) gets signal from the satellite.
- After that, the signals are sent to the wireless network via GPS receiver.
- The wireless network then sends these signals to the wireless server.
- Finally, the user can access their location via internet.
How much can you rely on the accuracy of GPS?
The accuracy of GPS depends on the type of receiver. Most of the user has the accuracy of about +/-10m. While other uses a method called Differential GPS (DGPS) to receive higher accuracy. To use DGPS you need an additional receiver fixed at the nearby location.
Sometimes you may not receive accurate positioning this happens due to signal blockage, radio jamming, solar storms, satellite maintenance etc.
Government’s contribution on ongoing GPS modernization program
To improve the accuracy level of the GPS, the government is undertaking many GPS modernization programs.
But the accuracy commitment doesn’t apply to the GPS devices, but it is rather for the signal broadcast in space. For instance, the government commits to transmit GPS signal in space with global average URE (user range error) of ≤7.8 m (25.6 ft.), with 95% possibility. The actual performance exceeded the requirement. On May 11, 2016, the global average URE was ≤0.715 m (2.3 ft.), 95% probability.
User Range Error is not user accuracy. User accuracy totally depends on the combination of satellite geometry, user range error and some of the local factors like the signal blockage, solar storm, and receiver design.
Is there any difference between military GPS and civilians in terms of accuracy?
During 1990, U.S. government used Selective Availability system to degrade the GPS accuracy for civilian use.
But in May 2000, the U.S. government at the direction of President Bill Clinton eliminated the use of Selective Availability to make GPS tracker technology more open for civil and commercial users.
After that, the user range error (URE) of the GPS signals is same for civilian and military. However, the civilian device uses only 1 GPS frequency, whereas the military receiver uses 2 GPS frequencies. Two GPS frequencies improve the accuracy by improving the signal distortions which is caused by Earth’s atmosphere. The dual-frequency GPS service is commercially available for the civilian, but the cost and size is limited to the professional applications.