Quality Assessment of Norrinteger-hour Data Blocks in GPS Broadcast Ephemeris

GPS broadcast ephemeris provides orbit and clock error for realtime positioning applications，thus any abnormal effect in the broadcast ephemeris could cause significant influence on the positioning solution.Due to firmware anomalies in the GPS satellite and the ground control segments，redundant navigation messages occur at times，i.e.another data block is unexpectedly generated 16*N(N=1，2，…，15)seconds prior to the GPST integer hour. These norrinteger-hour blocks however have not received much attention in terms of quality assessment. This paper first describes the three types of norrinteger-hour data blocks in UPS broadcast ephemeris. An assessment strategy is proposed so as to conduct a comparison between the norrinteger-hour and integer-hour data blocks with respect to the IUS final products. The results indicate that norrinteger-hour data blocks are not blunders.Such norrinteger-hour blocks can even provide better accuracies than corresponding integer-hour data blocks based on one-week UPS broadcast ephemerides. Finally，recommendations about how to utilize the UPS norrinteger-block data blocks are provided.