Augmentation of GPS for hydrographic applications under signal masking

In critical coastal water areas where signal masking due to high topographi c features is severe, GPS is known to be deficient in either one or both of two characteristics, namely availability and reliability, the latter being associated with the notion of quality assurance. Augmentation of GPS with either GLONASS and/or geostationary satellites, in addition to the use of h eight and clock constraints is becoming a viable alternative, the more so a s cost effective GPS/GLONASS receivers become available. The question as to what degree this combined approach can resolve the above limitations is an alyzed herein by first conducting a series of simulations and, second, by v alidating these simulations with actual marine tests. The simulations use w orst-case anisotropic mask angles encountered for specific locations along Canada's Pacific Coast. Availability is evaluated through dilution of preci sion (DOP), figures of merit, and reliability by infernal and external reli ability measures. The GPS/GLONASS/geostationary satellites analysis include s simulations with height and clock constraints to determine the impact of these constraints on availability and reliability. Each set of results are compared to GPS to assess the incremental benefits of each type of augmenta tion. The simulations are validated with actual DGPS/DGLONASS measurements collected on a survey launch off Sidney, B.C., Canada.