Over 10 years ago, a paper was published at the ION-GPS ‘99 conference that detailed the design of the navigation system implemented on the Global Hawk UAS program then being run under the auspices of DARPA. Since that time, many changes have occurred in the program including transition from DARPA to USAF management, the development of the larger Block 20/30 unmanned aircraft (UA) and the awarding of the Broad Area Maritime Surveillance (BAMS) program to Northrop Grumman which is based on the Global Hawk Block 20/30 aircraft. In addition, many changes have been made to the aircraft navigation system as well as many lessons learned on the kind of navigation system required to support a long endurance UA. The result has been a much more robust set of navigation sensors that allows this aircraft to successfully support the efforts to counter terrorism in the world today.1