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  • Files available:
    • GPS-satellite orbit + clock files (IGS .sp3 format)
    • Earth-orientation files (IGS .erp format)
  • Each file provides 48 hours of solutions:
    • 24 hours of post-processed solutions
    • 24 hours of predictions
    • These files are also available via anonymous ftp at
  • File name indicates center date/time of 48-hr span
    • before date = post-processed
    • after date = predict
  • Frequency/latency: produced every six hours, available three hours after center epoch.
  • File names (by example):
    • usu15002_18.sp3: 48-hr orbit/clock file with center date GPS week 1500, day 2 (Tuesday), hour 18 (GPST)
      • general format: usuwwwwd_hh.sp3
    • Similarly, usu15002_18.erp
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