Future multi-constellation Global Navigation Satellite Systems (GNSS) will offer the possibility to fulfill stringent navigation integrity requirements using Receiver Autonomous Integrity Monitoring (RAIM). This paper presents a detailed comparison of residual-based (RB) and solution separation (SS) RAIM. A complete step-by-step derivation of the two methods, which is currently missing in the literature, is given for the detection of single and multi-measurement faults, starting from common definitions of the integrity and continuity risks. In addition, a parity-space representation of SS RAIM is developed. It is shown that the integrity monitoring performance of SS RAIM can be superior to RB RAIM because SS test statistics are tailored to the fault hypotheses, and to the state of interest. However, for practical reasons of computational efficiency in conventional SS implementations, which are fully detailed in the paper, RB RAIM ultimately provides tighter bounds on integrity risk.

No 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.

The purpose of this study was to validate the appropriateness of the Comprehensive Vocational Evaluation System (CVES) for evaluating the work potential and independent living levels of visually impaired and blind individuals. The CVES was administered to 237 clients of the Texas Commission for the Blind (TCB), and the results were used to predict the vocational placement and independent living levels of these clients as determined by the TCB staff. The results indicated that the CVES is significantly related to work and independent living outcomes for visually impaired and blind people.

No abstract