Increase of a global navigation satellite system (GNSS) is a method of Improving the navigation system’s attributes, Such As accuracy, reliability, and availability, through the integration of external information into the calculation process. GNSS sensor receives the external information. Some of these systems provide additional information about sources of error (such as clock drift , ephemeris , or ionospheric delay ), others provide direct measurements of how much the signal was off in the past, Calculation process.
Satellite-based augmentation system
A satellite-based augmentation system (SBAS) is a system that supports wide-area or regional increases through the use of additional satellite-broadcast messages. Such systems are commonly composed of multiple ground stations, located at accurately-surveyed points. The GNSS satellites , the satellite signals, or other environmental factors which may impact the signal received by the users. Using these measurements, information messages are created and sent to one or more satellites for broadcast to the end users. SBAS is sometimes synonymous with WADGPS, wide-area DGPS . 
For details on how various SBAS are implemented, please see the following articles:
- The Wide Area Augmentation System (WAAS), operated by the United States Federal Aviation Administration (FAA).
- The European Geostationary Navigation Overlay Service (EGNOS), operated by the ESSP (on behalf of EU ‘s GSA ).
- The Multi-functional Satellite Augmentation System (MSAS) system, operated by Japan ‘s Ministry of Land, Infrastructure and Transport Japan Civil Aviation Bureau (JCAB).
- The Quasi-Zenith Satellite System (QZSS), proposed by Japan.
- The GPS Aided Geo Augmented Navigation (GAGAN) system being operated by India .  
- The GLONASS System for Differential Correction and Monitoring (SDCM), proposed by Russia .
- The Satellite Navigation Augmentation System (SNAS), proposed by China .
- The Wide Area GPS Enhancement (WAGE), operated by the United States Department of Defense for use by military and authorized receivers.
- The commercial StarFire navigation system , operated by John Deere and C-Nav Positioning Solutions ( Oceaneering ).
- The commercial Starfix DGPS System and OmniSTAR system, operated by Fugro
- The GPS · C , short for GPS Correction, was a Differential GPS data source for most of Canada ‘s Active Control System, part of Natural Resources Canada – now decommissioned.
Ground-based augmentation system
Each of the ground-based augmentation system (GBAS) and ground-based regional augmentation system (GRAS) describes a system that supports increases through the use of terrestrial radio messages. As with the satellite-based augmentation system , the ground-based augmentation systems are commonly referred to as “GNSS”, and one or more radio transmitters, which transmits information directly to the end user GEO Satellites at high altitudes.
Generally, GBAS is localized, supporting receivers within 23 nautical miles, and transmitting in very high frequency ( VHF ) band.
The shorter the distance between the ground station that calculates the differential corrections to the inbound plane, the higher the accuracy is likely to be. There is a need for a high-quality, high-performance, low-cost, high-performance, II / III conditions) for which SBAS is not intended or suitable. 
Various ground-based augmentation systems
- International Civil Aviation Organization Ground-Based Augmentation System (GBAS) Originally this system was called the Local Area Augmentation System (LAAS)
- The US Nationwide Differential GPS System (NDGPS), an increase system for users on US land and waterways. 
- See also, the Differential GPS (DGPS) Wikipedia page
Aircraft-Based Augmentation System (ABAS)
The increase may also take the form of additional information from navigation sensors being blended into the position calculation, or internal algorithms that improve the navigation performance. Many times the additional avionicsoperate via GNSS and are not necessarily subject to the same sources of error or interference. A system such as this is referred to as an aircraft-based augmentation system (ABAS) by the ICAO. The most widely used form of ABAS is Receiver Autonomous Integrity Monitoring (RAIM) , which uses redundant GPS signals to ensure the integrity of the position solution, and to detect faulty signals. 
Additional sensors may include:
- ELORAN receivers
- Automated Celestial navigation systems
- Inertial Navigation Systems
- Simple Dead reckoning systems (composed of a gyro compass and a distance measurement)
- Assisted GPS (A-GPS)
- GNSS enhancement
- Jump up^ Kee, C. Parkinson, BW, and Axelrad, P. (1991), “wide area differential GPS” navigation, Journal of the Institute of Navigation, 38, 2 (Summer 1991), <http: / /ion.org/search/view_abstract.cfm?jp=j&idno=207>
- Jump up^ http://isro.gov.in/pressrelease/scripts/pressreleasein.aspx?Jan03_2014
- Jump up^ http://www.thehindu.com/news/national/kerala/gagan-system-ready-for-operations/article5565700.ece
- Jump up^ http://www.gps.gov/multimedia/presentations/2011/09/ICG/lawrence.pdf
- Jump up^ US Government page on GPS augmentation systems
- Jump up^ ICAO (2005). Global Navigation Satellite System (GNSS) Manual (PDF) (First ed.).