Recovering UTC (USNO,MC) with Increased Accuracy Using a Fixed, L1-CA Code, GPS Receiver; Conference paper

摘要

The accuracy with which a L1, single-frequency, GPS receiver can recover the time-scale UTC (USNO,MC) is well known to depend on many factors, including the accuracy of the signal in space, propagation path effects, the qualify of the GPS/UTC (USNO,MC) correction, and the behavior of the receiver itself. Overall performance is now affected by a number of short- and medium- term noise sources that have hitherto been obscured by the intentional clock dither known as Selective Availability (SA). We report the development of a technique for periodically estimating the local ionospheric delay from observations of the code and carrier-phase GPS observables made with a multi- channel, L1, receiver module. An algorithm has been developed that uses information from several satellites to model the delay in real time. It is then possible to correct the raw time estimate from each satellite, improving the overall accuracy of the receiver's real-time estimate of GPS time or UTC(USNO, MC). With this technique it should be possible to approach the time accuracy obtained using a Precise Positioning Service (PPS) receiver. We have used a cesium standard ensemble related to UTC (USNO,MC) by common-view to measure the noise level obtained by applying the estimated corrections, and to compare this with the accuracy of the built-in single-frequency model.