The National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT) has released an updated civil GPS Standard Positioning Service Performance Standard, committing the United States Department of Defense (DoD) to an improved level of GPS accuracy for civilian signals.
It is the fourth revision of the standard positioning service (SPS) performance standards document, and the first update since October 2001. In addition to specifying GPS minimum performance commitments, the SPS performance standard serves as a technical document designed to complement the GPS Signal in Space (SIS) Interface Specification.
The most significant change in the updated SPS standards is a 33 percent improvement in the minimum level of SIS range accuracy, from 6 meters root mean square (rms) accuracy to 4 meters rms (7.8 meters, 95 percent), according to the document, which is drafted by the DoD and released through the PNT committee.
While the stated dedication to improvement is notable, it has a built-in conservative margin for minimum performance; as the documents authors note in the executive summary: "with current (2007) SIS accuracy, well designed GPS receivers have been achieving horizontal accuracy of 3 meters or better and vertical accuracy of 5 meters or better, 95 percent of the time."
The full SPS document can be found on the National Executive Committee for Space-Based Positioning, Navigation, and Timing website.
