CNAV on L2C and L5 Initiated

摘要

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 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-in-space 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.