Satellite‐Based Augmentation Systems (SBASs)

The concept of Satellite‐Based Augmentation System (SBAS) has its roots in the 1980s. An SBAS is a system designed to improve global navigation satellite system (GNSS) service such that the augmented service meets the strict requirements of air navigation. This chapter uses the existing Wide Area Augmentation System L1 design to describe the different SBAS monitors. The SBAS protection level equations are based upon the observation that the error sources are approximately Gaussian and that an inflated Gaussian model can be used to conservatively describe the positioning errors. The SBAS integrity parameters sent to the users are the user differential range errors to bound the ranging errors to a specific satellite and the grid ionospheric vertical errors to bound the estimated errors in the SBAS ionospheric delay model. The chapter is intended to provide an overview to assist the reader in understanding how the different message types connect together to form a differential GPS correction.