SBASsystemer

SBASsystemer, shorthand for Satellite-Based Augmentation Systems, are networks designed to enhance the performance of global navigation satellite systems (GNSS) by providing corrections, integrity information, and wide-area coverage. The main goal is to improve positioning accuracy, reliability, and availability for civilian users, including aviation, maritime, and surveying.

A typical SBAS consists of a network of ground reference stations that monitor GNSS satellite signals, a master control center that computes corrections and integrity data, uplink stations, and geostationary satellites that broadcast the augmentation messages to users. The corrections include satellite orbit and clock errors, ionospheric delay estimates, and integrity information about satellite health and signal availability. The information is encoded in SBAS messages and transmitted in dedicated channels on the GEO satellites, allowing users with compatible receivers to apply corrections in real time.

Regional systems include WAAS in North America, EGNOS in Europe, GAGAN in India, and MSAS in Japan. These systems are designed primarily to augment GPS, but many modern receivers can also incorporate other GNSS signals. The orientation is to support improved navigation accuracy and to enable APV (Approach with Vertical Guidance) operations in aviation within the SBAS service areas.

Limitations include dependency on the GEO satellite coverage, regional extent of the SBAS, and the requirement for compatible user equipment. SBAS does not provide global corrections everywhere, and performance can vary with satellite geometry and ionospheric conditions.

Overall, SBASsystemer play a central role in modern GNSS infrastructure by delivering regional accuracy and integrity enhancements that support safety-critical and precision applications.