• Version
• 347 Downloads
• 9.36 MB File Size
• 1 File Count
• April 28, 2016 Create Date
• April 28, 2016 Last Updated

Differential Global Positioning System (DGPS) for Flight Testing

Historically, test ranges have provided accurate time and space position information (TSPI) by using laser
tracking systems, kinetheodolite systems, tracking radars, and ground—based radio positioning systems.
These systems have a variety of limitations. In general, they provide a TSPI solution based on
measurements relative to large and costly fixed ground stations. Weather has an adverse effect on many of
these systems, and all of them are limited to minimum altitudes or confined geographic regions.
The Global Positioning System (GPS) provides a cost-effective capability that overcomes nearly all the
limitations of existing TSPI sources. GPS is a passive system using satellites, which provides universal
and accurate source of real—time position, and timing data to correlate mission events. The coverage area is
unbounded and the number of users is unlimited. The use of land-based differential GPS (DGPS)
reference stations improves accuracy to about one meter for relatively stationary platforms, and to a few
meters for high performance tactical aircraft. Further accuracy enhancement can be obtained by using GPS
carrier phase measurements, either in post-processing or in real—time. Accuracy does not degrade at low
altitudes above the earth’s surface, and loss of navigation solution does not occur as long as the antenna
has an open view of the sky. Therefore, it was important to undertake a study in order to investigate the
range of possible applications of DGPS in the flight test environment, taking also into account possible
integration (in real-time and in post-processing) with other systems.
In this AGARDograph, the potential of DGPS as a positioning datum for flight test applications is deeply
discussed. Current technology status and future trends are investigated in order to identify optimal system
architectures for both the on—board and ground station components, and to define optimal strategies for
DGPS data gathering during various flight testing tasks. Limitations of DGPS techniques are deeply
analyzed, and various possible integration schemes with other sensors are considered. Finally, the
architecture of an integrated position reference system suitable for flight test applications is identified.
The purpose of this AGARDograph is to provide comprehensive guidance on assessing the need for and
determining the characteristics of DGPS based position reference systems for flight test activities.
The specific goals are to make available to the NATO flight test community the best practices and advice
for DGPS based systems architecture definition and equipment selection. A variety of flight test
applications are examined and both real-time and post-mission DGPS data requirements are outlined.
Particularly, DGPS accuracy, continuity and integrity issues are considered, and possible improvements
achievable by means of signal augmentation strategies are identified.