The Global Positioning System: A Shared National Asset (1995)
Chapter: Oceanography
Table 2-8 GPS Earth Science Requirementsa
Challenges to Full GPS Utilization
Meteorology
A third GPS radio frequency would be very helpful in atmospheric studies. Also, the presence of A-S greatly increases costs and limits the performance of many techniques due to loss of low-elevation angle data and signal-to-noise ratio, even when using dual-frequency codeless receivers.
Oceanography
In general, spacecraft orbits determined from GPS data with A-S off are superior to those determined by other means, with A-S on this is not the case. A successor mission to Topex/Poseidon could be designed with receivers that would work well in the presence of A-S and, essentially, overcome this obstacle. However, it has been estimated that the additional cost of adding a space-qualified PPS receiver to a satellite would be about $500,000.38 Much of this cost stems from the security measures that are required for the proper handling of classified equipment.
For other types of oceanographic research, SA is the central challenge to the usefulness of GPS. The 10-meter to 30-meter accuracies required to navigate research vessels, position buoys, and locate objects on the ocean floor cannot be achieved using GPS
