GPS provides two LEVELS of service -- a Standard Positioning Service (SPS) for general public use and an encoded Precise Positioning Service (PPS) primarily intended for use by the Department of Defense. SPS signal accuracy is intentionally degraded to protect U.S. national security interests. This process, called Selective Availability (SA), controls the availability of the system's full capabilities. The SPS accuracy specifications, given below, INCLUDE the effects of SA.

SPS provides accuracies of (for position, the accuracy with respect to geographic, or geodetic coordinates of the Earth) within:

100 meters (2 drms) horizontal 156 meters (2 SIGMA) vertical 300 meters (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)

SPS Coverage is continuous and worldwide, with a position dilution of precision (PDOP) of 6 or less.

GPS provides two levels of service -- a Standard Positioning Service (SPS) for general public use and an encoded Precise Positioning Service (PPS) primarily intended for use by the Department of Defense. SPS signal accuracy is intentionally degraded to protect U.S. national security interests. This process, called Selective Availability (SA), controls the availability of the system's full capabilities. The SPS accuracy specifications, given below, include the effects of SA.

SPS provides accuracies of (for position, the accuracy with respect to geographic, or geodetic coordinates of the Earth) within:

100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)

SPS Coverage is continuous and worldwide, with a position dilution of precision (PDOP) of 6 or less.