GPS World, June 2014

THE SYSTEM New Loran at 5 Meters Dutch consultants Reelektronika showed results from a prototype enhanced differential Loran eDLoran system extensively tested in the Europort Rotterdam area at the European Navigation Conference held in April The tests achieved accuracies of 5 meters A full technical article describing the equipment methodology and test results will appear in the July issue of GPS World Harbor pilots require accuracies of 5 meters and some form of robustness or back up for GNSS systems in case of jamming unintentional interference system failure or other disruption The current eLoran system cannot get better than 10 meter accuracy The new eDLoran opens up new possibilities for multiple applications Installing eDLoran reference stations is fast simple and cost effective As there is no data channel bandwidth limitation multiple reference stations can be installed which offers increased reliability the red trACk is based on raw eLoran data without any corrections The transparent blue line is made by GPS RTK and is widened to 10 meters giving the required 5 meter limits of eDLoran The white line is output from the eDLoran receiver which stays within the borders of the 10 meter wide transparent blue line A single or multiple eDLoran servers CNAV on L2C and L5 Initiated On April 28 U S Air Force Space Command began broadcasting civil navigation CNAV messages on all operational GPS satellites capable of transmitting the L2C and L5 signals L2C is designed for commercial needs and L5 meets safety of life transportation requirements These new CNAV messages will enable manufacturers to develop and test advanced civil receivers and make for a more robust position navigation and timing PNT solution available to the civilian public said Maj Gen Robert E Wheeler We do not anticipate any GPS satellite outages or legacy degradations as a result of the pre operational deployment of these frequencies and those currently using the GPS Standard Positioning Service should not be impacted Initial CNAV broadcast occurs at a and makes the system more robust against terrorism and lightning damage can be installed in a protected area There is hardly a practical limit in the number of differential reference stations to serve reduced data accuracy and update frequency compared to GPS signals in use today In December 2014 CNAV data updates will increase to a daily rate bringing L2C and L5 signal inspace accuracy on par with legacy signals However derived position accuracy cannot be guaranteed during the pre operational deployment These signals are primarily used to test various equipment and should be employed at the users own risk not used for safety of life or other critical purposes The Air Force will broadcast L2C messages with the health bit set healthy as was the case during a June 2013 test L5 messages will be set unhealthy but as experience grows with L5 broadcast and implementation of signal monitoring is achieved this status may change upon review Reshaping the limits of positioning T e AsteRx3 is a key enabler for our superior performance in urban canyons Xavier Montazel head of iXBlue Inertial Products division You need precise positioning in challenging environments You want Septentrio Versatile OEM Receivers for Demanding Applications GPS World June 2014 www gpsworld com 8