Ramon Lopez/WASHINGTON DC
A STUDY ORDERED by US Congress says, that the Pentagon should retain control of the global positioning system (GPS), but that it should not be able to degrade the accuracy of GPS signals to civil users.
The report, issued jointly by the National Academy of Public Administration and the National Research Council, says that, "an important factor that undercuts GPS satellite improvements and inhibits foreign willingness, to rely on the system is selective availability, which the Pentagon uses to degrade the accuracy of the civil GPS signal".
The report adds, "Selective availability sustains foreign doubts about the US commitment to offer GPS as a global utility for the indefinite future. Some foreign governments and international organisations are understandably reluctant to make a full commitment to the system, while the DoD [Department of Defense] reserves the right to dither with the accuracy of the signal."
The Pentagon should develop the capability to counter adverse use of GPS, continues the report, using methods other than those used to corrupt the GPS signals. The DoD should instead depend on a strategy of denying radio-navigation signals to the enemy.
The panel also recommends that the USA add a second civilian signal to GPS space craft, which allows for correction of errors introduced by the ionosphere.
The accuracy level for civil users is 100m. In contrast to the standard-positioning service (SPS), the US military is offered precise-positioning service accuracy of 21m. The full accuracy capability of GPS is denied to SPS users through selective availability. Differential GPS is an available method used to improve the basic GPS signal, however.
Source: Flight International