Evaluation of Signal in Space Error Bounds to Support Aviation Integrity

The modernization of GPS and the addition of new GNSS constellations bring forth a multitude of new signals with new capabilities. One of the intended purposes of some of these new signals is the provision of high integrity positioning sufficient for use in aviation. However, one must be extremely cautious, as the integrity requirements for aviation, particularly precision approach, are very strict. There must be less than a one in ten million chance of providing misleading information to the pilot. Further, each individual nation is responsible for approving equipment and procedures in their sovereign airspace. In order to make use of signals over which they have no control, aviation authorities must have a clear understanding of the commitments and capabilities of these new signals. These authorities will also likely want to monitor the signals to ensure that they are conforming to their intended design. This paper proposes equations to combine information from the satellites together with other error bounds to form appropriate upper bounds on the users' position estimates. The position domain bounds, called protection levels, are matched to proposed data monitoring criteria that ensure consistency between what has been observed and what is assumed by the bounding equations. The protection level equations, their matching monitoring criteria, and their mathematical link are the main topics of this paper.