Performance Analysis of Carrier-Phase DGPS Navigation for Shipboard Landing of Aircraft

Abstract

Shipboard-relative GPS (SRGPS) is a variant of the Joint Precision Approach and Landing System (JPALS) that is being developed to support automatic shipboard landings in zero-visibility conditions. At present, the navigation system requirements specify a vertical protection level of 1.1 m, an integrity risk of approximately 10⁻⁷, and a system availability of at least 99.7 percent. Because of the stringent nature of these specifications, differential carrier-phase solutions are being pursued. In this context, this paper gives a detailed analysis of the fault-free integrity and availability of SRGPS. The performance of single- and dual-frequency architectures is evaluated for both floating-ambiguity and fixed-integer carrier-phase differential GPS (DGPS) navigation. The sensitivity of SRGPS availability is quantified with respect to raw code and carrier measurement quality, spatial decorrelation of ionospheric and tropospheric errors, and broadcast service radius. Necessary conditions to achieve the desired navigation performance are defined.