GPS World, February 2014

THE SYSTEM U S Transport DepSec Takes Potshot at CNAV The departing Deputy Secretary of Transportation John Porcari wrote a letter in the closing days of 2013 opposing the U S Air Forces announced plans www gpsworld com afcnav to begin broadcasting Civil Navigation CNAV message populated L2C and L5 signals as early as April 2014 Military personnel are incensed over what they see as Porcaris impugning when not ignoring the Air Force 35 year track record of broadcasting the gold standard of global navigation satellite signals something in which Transportation has zero experience Porcari alludes in his December 27 letter to non standard engineering tools and non standard operations that he believes would come into play for early CNAV broadcast These have the potential to inject human error which may result in unacceptable GPS constellation operation What Porcari means by nonstandard he does not specify although he confesses to unease as the ability to monitor these signals without which the system will not know if the L2C and LS signals are within specification Given these risks DOT is concerned that the CNAV messages could provide hazardously misleading information impacting GPS safety of life protection of property and economic security applications The full text of the Porcari letter is available at www gpsworld dotcnav OCX Delay the Cause Because the current GPS ground control system cannot generate CNAV and the next generation OCX which can will not be ready by April another computer will apparently develop the civil signal navigation data However neither the data or message is intended for actual use nor will the FAA or any transport agency employ it The advance project is designed to aid receiver manufacturers and developers in adopting to the new signal In addition to questioning Air Force 2 SOPS ability to broadcast an accurate compliant signal containing CNAV the letter appears to ignore or be ignorant of the 17 official U S government military monitoring sites for GPS distributed around the world not to mention thousands of other monitoring sites run by government agencies such as the Jet Propulsion Laboratory the National Aeronautics and Space Administration and the National Geospatial Intelligence Agency and by many universities such as Stanford Ohio State Cal Tech and many other international institutions around the world Many of these sites collaborate under the rubric of the International GNSS Service Finally John Deere and Trimble Navigation both operate automated GPS signal monitoring systems that that report any anomaly in the navigation message for all GPS signals with an average two second notification time This letter is so much BS fumed one source who wished to remain anonymous coming from an agency that is in arrears in its GPS payments to the tune of more than 70 million and has no clue how to represent the global GPS user GPS is a ubiquitous system not just a tool for the DOT and the Federal Aviation Administration GPS needs to implement these signals for all users and as a modernization program that was promised to be in place years ago Porcari left for the private sector www gpsworld com February 2014 GPS World 11