A ground based augmentation service for gate-to-gate operations

The rationale for augmentation services in general is to improve GNSS integrity and to overcome guaranteed service availability in GNSS (GPS and Glonass). For certain operations where high accuracy is needed, augmentation is also required. The ground based regional augmentation system (GRAS) is receiving growing interest as a complement, and in some areas of the world alternative, to spaced based augmentation system (SBAS). The service GRAS delivers to the users can either be used as is for navigation only but can also be used by non-navigation functions, e.g. automatic dependent surveillance broadcast (ADS-B). It is important that the total communication, surveillance and navigation (CNS) architecture is developed with this in mind, that maximum synergy is achieved, achieving seamless gate-to-gate operations etc., still maintaining sufficient partitioning not to compromise safety. This paper discusses GRAS from two viewpoints-navigation-as complement to the European SBAS (EGNOS) and-surveillance-ADS-B. The paper also discusses new development assumptions, such as SA and Galileo, to take into account when designing GRAS.