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A Selective Availability Anti-spoofing Module (SAASM) is used by military Global Positioning System receivers to allow decryption of precision GPS observations, while the accuracy of civilian GPS receivers may be reduced by the United States military through Selective Availability (SA) and anti-spoofing (AS). [1]
A choke ring antenna is a directional antenna designed for reception of GNSS signals from satellites. It consists of a number of concentric conductive cylinders around a central antenna. The first choke ring antennas were invented at JPL; [2] since 1989 they have been improved and extended by many companies. [citation needed]
DGPS Reference Station (choke ring antenna)A reference station calculates differential corrections for its own location and time. Users may be up to 200 nautical miles (370 km) from the station, however, and some of the compensated errors vary with space: specifically, satellite ephemeris errors and those introduced by ionospheric and tropospheric distortions.
Trimble Inc. is an American software, hardware, and services technology company. Trimble also does hardware development of global navigation satellite system (GNSS) receivers, scanners, total stations, laser rangefinders, unmanned aerial vehicles (UAVs), inertial navigation systems and software processing tools.
A GPS receiver processes the GPS signals received on its antenna to determine position, velocity and/or timing. The signal at antenna is amplified, down converted to baseband or intermediate frequency, filtered (to remove frequencies outside the intended frequency range for the digital signal that would alias into it) and digitalized; these ...
Controlled reception pattern antennas (CRPA) are active antennas that are designed to resist radio jamming and spoofing. They are used in navigation applications to resist GPS spoofing attacks. [ 1 ] [ 2 ]
This is because wavelength is inversely proportional to frequency (wavelength in metres = 299,792,458 / frequency in Hz), and transmitter efficiency is severely degraded if the length of the antenna is shorter than 1/4 wavelength. They used grounded or insulated guyed masts with umbrella antennas, or wire-spans across both valleys and fjords.
The AN/PSN-13 Defense Advanced GPS Receiver (DAGR; colloquially, "dagger") is a handheld GPS receiver used by the United States Department of Defense and select foreign military services. It is a military-grade, dual-frequency receiver, and has the security hardware necessary to decode the encrypted P(Y)-code GPS signals .