Expert panelists, one from a company working with the GPS Wing to explore solutions to the SVN49 problem, discussed technical details of the signal anomaly and various solution options, in a live webinar sponsored by GPS World on November 17.  The audio portion of the webinar and all Powerpoint slides by both speakers and the moderator are available free for download.

The SVN 49 problem consists of larger than normal pseudorange errors broadcast by the newest GPS satellite. The error still lies within GPS system specifications, but is larger than that of other satellites; the pseudorange error is greater when the satellite is at higher elevation.

Peter Boulton of Spirent Communications discusses how his company, in conjunction with Spirent Federal, is working with the GPS Wing to simulate the anomaly so that receiver manufacturers can test possible simulated solutions on their equipment. His subtopics include: Simulating the Variation with Elevation Angle; UCD file structure –Varying the power level; UCD file structure –Phase Inversion; Removing the Anomaly from Simulation; Partial Fix ? Simulating the Phase Centre Offset; and Simulating the Undeclared Clock Bias

Greg Turetzky of SiRF/CSR then gives the perspective of a manufacturer supplying the consumer market with L1-only chipsets, where the signal anomaly is less noticeable. He posits that a partial signal fix may do more harm than good, because consumer units cannot support treating PRN1 differently from other signals.

The speakers then answer questions from the live webinar audience.