A Study on the DGPS Protection Level for Navigation in Harbour Entrances and Approaches

Abstract

International Maritime Organization recommends the GNSS integrity requirements for maritime safety. This paper focuses on calculation method of protection level which necessary to DGPS integrity monitoring for safe navigation in harbor entrances and approaches. Based on previous studies, the UDRE from DGPS reference station is used for calculate the DGPS protection level. But the UDRE is designed to be bigger than own true value always and consequently calculated protection level is higher than own true value also. Higher protection level is more often over the threshold. If the protection level exceeds the threshold, the measured position cannot be used. This reduces the availability of the DGPS System. Therefore, in order to avoid decrease of availability, this paper proposes a method to calculate the protection level more precisely by estimates error of the pseudorange correction instead of using the UDRE. In conclusion, use of the proposed method can lead to increase of the DGPS availability performance.