GPS World, December 2014
EXPERT ADVICE Year GPS RMS URE GPS II IIA GPS IIR 2006 110 cm 16 12 1 0 29 15 3 0 44 2014 59 cm 5 12 7 7 31 25 16 TABLE 1 Differences in GPS service between 2006 and 2014 This has been done GPS went from one IIR M satellite in 2006 to the present seven IIR M satellites and seven IIFs They provide a new civil signal on L2C and the IIF provides a new civil safety of life signal on L5 Lets look at the differences in service between 2006 and 2014 as shown in TABLE 1 GPS RMS user range error URE has been cut in half and the number of usable GNSS satellites has gone up by 39 percent 44 to 61 Today GPS and GLONASS operate at full capacity GPS exceeds GPS IIRM GPS IIF GPS Tot GLONASS BeiDou Galileo GNSS BeiDou open interface speci cation not issued until 2011 test signals Sources GPS World Almanac 2006 2014 Update on GPS Program Stanford PNT Symposium its marks by providing 31 satellites broadcasting signal in space range errors in the half meter range even as Block IIF satellites add L2C and L5 signals GPS high precision users also employ space based augmentation systems services such as WAAS EGNOS and QZSS Internet connected GPS receivers including those in cellular phones use Assisted GPS to provide near instantaneous times to first fix One drawback to GNSS is its undependability when subjected to blockage interference or spoofing Avail 5 MEO 3 61 GNSS services should be made more resilient and PNT users must diversify their positioning sources We are now moving into a hybrid world in which PNT services go far beyond just GPS to multi GNSS services augmented by other PNT technologies including assisted GNSS inertial sensors and terrestrial positioning services Although diversifying PNT sources increases cost it may not be as much as some might think At a recent PNT symposium at Stanford University Greg Turetzky of Intel predicted VIC100 Series GPS Precision Timing Antennas Standard and Enhanced Filter Models Secure Performance by attenuating noise and interference near GPS L1 frequency through triple and enhanced quad fltering designs Durable and Reliable in severe environments RoHS Compliant http www panasonic com gps www gpsworld com December 2014 GPS World 43
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