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The current project aims at the development of a cost-effective and efficient laboratory facility for thoroughly evaluating the capability of GPS-based integrated navigation systems, including aero delivery systems. The ability to test navigation system components, GPS receivers, IMU sensors, and software constitutes a critical part of the research and development process. As the demand for GNSS products has increased, more receiver manufacturers and application developers have entered the market, GPS and GNSS simulators have increased became a bellwether for the GNSS industry, both mass market and professional. The term GPS simulator is widely used, encompassing something as simple as a piece of software outputting an NMEA position and velocity string. However, for professional OEM the term more usually refers to a device which provides signals to the RF section of a GPS receiver, that is, as if the signals were coming from an antenna. In turn a GNSS simulator provides signal characteristics for both existing systems, such as GPS or GLONASS, and systems in deployment, such as Galileo and QZSS. There are two techniques in common usage. The first records and replays real-world RF signals from navigation satellites. The second uses software simulators combined with signal generators to replicate navigation satellite RF signals.

This ongoing project is based upon, is a GPS constellation simulator which generates up to 32 GPS SVs of C/A, P code, and M-noise on L1 and L2. Vehicle dynamics, multipath, and atmospheric conditions are user-configured and generated as part of the simulation. The system under test (its GPS receiver) will experience the same RF inputs that would exist in an operational scenario, but in a controlled and repeatable laboratory environment. This capability will allow analyzing dynamic performance and operational capability of any GPS-based navigation system at a detailed level that is not possible with actual flight tests. In addition to this a lot of the tests could be replaced with just computer simulations, especially for the initial stage of the development / testing of new systems. The system under test could be placed in any “virtual” location (war zones), and any constellation of up to 32 satellites (including the U.S. NAVSTAR GPS, Russian GLONASS, European Galileo and Chinese Beiduo) with associated environmental and orbit parameter errors can be simulated. The satellites can be made to appear and disappear at will, in order to test the acquisition and re-acquisition capability of the GPS receiver. In addition, interference, spoofing (for SA/AS equipped systems), multipath and clear environments can be modeled through computer controls. The development environment will also allow to investigate the use of auxiliary measurements (e.g., barometric and radar altimeter, Doppler radar and attitude heading reference system). For the aero delivery systems it will also incorporate YPG winds database to show the effect of changing winds as well. The vehicle models will include a complete six degree of freedom models of a generic aircraft, UAV, parafoil-based delivery system, helicopter, armed vehicle, etc. We also intend to allow this development environment to be used in conjunction with another system that would allow receiving, visualizing and analyzing the real test (drop) data in real-time. In such a case along with a real (single) set of the test data, we would have multiple “virtual” realizations of this test showing what would happen if… GPS signal is jammed, spoofed, or some other elements of GPS-based integrated navigation system fail.

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