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CNAV PERFORMANCE

A quarterly meeting of the U.S. GPS Program's interagency Civil Navigation Signals (CNAV) Tiger Team occurred 5 March 2015 to discuss 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) & eight GPS IIF satellites (L2C & L5). A Modernized Navigation (MODNAV) Tool integrated with the GPS ground control software (Architecture Evolution Plan or AEP) is generating the CNAV data messages. Daily CNAV uploads began 31 December 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.

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.

The image below illustrates the above explanation; it is recommended that you click on the image to view a larger, more clear version in a new browser window.

CNAV and LNAV Performance Chart