Date Added: Apr 2010
All GPS satellites broadcast a User Range Accuracy (URA) parameter that may be used to statistically characterize the Instantaneous User Range Error (IURE) due to the satellite Signal In Space (SIS). As the performance of GPS has evolved and improved, the URA has taken on a very specific role for defining integrity guaranteed for the GPS SIS. The integrity performance guarantee may be stated as "The probability per hour per signal-in-space that the IURE exceeds the NTE Tolerance without a Timely Alert shall be ? P".