Evaluation of commercial carrier phase-based WADGPS services for marine applications

A number of GPS augmentation systems have recently been developed for different applications in various regions. The manufacturers of these commercial services claim decimeter or near-decimeter level (1σ) horizontal positioning precision. These systems provide different types of correction and integrity signals to users via satellite links. Three services were studied: the NavCom Technology, Inc. Starfire / C&C Technologies, Inc. CNav; the Fugro Chance Inc. Starfix-HP; and the Thales GeoSolutions Group Ltd. SkyFix XP. The University of Southern Mississippi Hydrographic Science Research Center’s (USM HSRC) primary goal was to evaluate how each system performed, with respect to criteria including: positioning solution availability, precision, accuracy, and integrity. No attempt was made to compare or contrast these products. The evaluation was performed within the context stringent marine application requirements provided by the International Hydrographic Organization (IHO) specifications for nearshore vertical positioning in hydrographic surveys. However, the results presented are of use to all GPS users, as these WADGPS services maintain significant landbased coverage. The evaluation results indicate that for the data collected the services can provide decimeter or near-decimeter vertical positioning precision at the 1σ level after tens of minutes of operation in both static and kinematic environments. GPS satellite viewing geometry and small biases mean that the services do not meet the highest IHO vertical positioning specifications. More data collection and analysis are needed to better characterize the performance of each system.