CNAV Performance ‘Matches or Slightly Outperforms’ Legacy Signals

March 19, 2015  - By

CNAV_Performance Chart_10_Mar_2015_public

A quarterly meeting of the U.S. GPS Program’s interagency Civil Navigation Signals (CNAV) Tiger Team on March 5 focused on the new L2C and L5 GPS civil signals. “CNAV Message Types 10, 11, 30 and 33 are currently transmitted on seven GPS IIR-M (L2C) and eight GPS IIF satellites (L2C and L5),” wrote Rick Hamilton, CGSIC Executive Secretariat, USCG Navigation Center, in a status email to the Civil Global Positioning System Service Interface Committee (CGSIC).

“A Modernized Navigation (MODNAV) Tool integrated with the GPS ground control software (Architecture Evolution Plan or AEP) is generating the CNAV data messages,” Hamilton wrote. “Daily CNAV uploads began December 31, 2014, and the U.S. Air Force reports that signal performance of CNAV matches or slightly outperforms Legacy performance: average user range error (RMS URE) from 25 February – 3 March 2015 was 0.50 m for Legacy and 0.57 m for Modernized; best week for Modernized signals since the broadcast initiated April 2014 was 0.42 m for 6 – 13 January 2015.

The graph above, from the Coast Guard Navigation Center website, illustrates the CNAV performance.

Users are reminded that these CNAV signals are ‘pre-operational’ and should be used with discretion until they become fully operational; the L5 message is currently set unhealthy,” Hamilton concluded.

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