Use of Military GPS in a Civil Environment

D.A. Happel

Abstract:	The United States Department of Defense (DOD) has a significant investment in the development of GPS technology. The commercial world has expanded both the scope and role of GPS technology and, using Standard Positioning Service (SPS) or Coarse Acquisition (C/A) receivers, has developed certification standards for use as navigation sensors by aircraft flying in commercial airspace. Through the use of Precise Positioning Service (PPS) capability, or P(Y) code receivers, DOD GPS receivers can maintain high levels of accuracy and integrity even in the presence of jamming. Use of PPS GPS, blended with inertial or terrain following sensors, provides extraordinary navigation capability. Certification agencies have rigid certification standards that must be met order to fly in commercial airspace. These standards are a function of the navigation sensor being used in the aircraft. With details associated with the implementation of PPS equipped GPS units being classified, getting certification of aircraft that plan to use PPS GPS receivers in commercial airspace can be difficult. As a result of the congressional mandate to install GPS on all military aircraft by the year 2000, a large number of military aircraft have highly accurate multi-sensor navigation systems that use PPS GPS receivers. The military sensors and integration techniques are often complex and tailored for specific military missions, such as low level flight, terrain following, weapon delivery, etc. As a result, the military users have a large investment in their existing integrated navigation function that must be retained to meet their mission requirements. This paper describes a patented means by which a navigation system can utilize the precise positioning information from a military navigation function utilizing sensors, such as a PPS GPS compliant receiver, in commercial airspace and meet all civil certification requirements. This is accomplished by using an approved civil navigation sensor as a monitor while enabling use of a PPS GPS military solution as the primary navigation source. This paper specifically addresses using a blended INS/GPS solution, typically from an Embedded GPS/INS (EGI) sensor, as the primary navigation source and using a TSO certified DO-229A compliant GPS receiver as a monitor in a configuration that meets Required Navigation Performance (RNP) requirements as defined by RTCA/DO-236, Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation. However, this concept can be extended to other sensor configurations to increase the integrity and continuity of the overall navigation system that will be needed by systems that must meet RTCA/DO-236 RNP requirements.
Published in:	Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003) June 23 - 25, 2003 Hyatt Regency Hotel Albuquerque, NM
Pages:	57 - 64
Cite this article:	Happel, D.A., "Use of Military GPS in a Civil Environment," Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003), Albuquerque, NM, June 2003, pp. 57-64.
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