Satellite-Based Augmentation Systems

Satellite-Based Augmentation Systems (SBASs) provide three main benefits to users of the augmented satnav system that includes integrity, accuracy, and availability. This chapter provides a brief history of SBAS, followed by an overview of SBAS and of some specific SBASs. SBAS coverage continues to expand, as existing systems add more satellites and ground reference stations, and additional systems are implemented. SBAS signals are designed primarily to provide data that communicates the integrity of augmented signals, as well as corrections that improve the accuracy of augmented signals; only some SBAS signals are currently approved for ranging. The high degree of interoperability between SBAS signals and corresponding GPS signals enables SBAS functionality to be added to a GPS receiver with minimal additional complexity. SBAS signals employ BPSK-R spreading modulations, no pilot components, and other design characteristics very similar to the GPS C/A code signal and L5 signal.