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There are four GPS signal specifications designed for civilian use. In order of date of introduction, these are: L1 C/A, L2C, L5 and L1C. [1] L1 C/A is also called the legacy signal and is broadcast by all currently operational satellites. L2C, L5 and L1C are modernized signals and are only broadcast by newer satellites (or not yet at all).
Initially, the highest-quality signal was reserved for military use, and the signal available for civilian use was intentionally degraded, in a policy known as Selective Availability. This changed on May 1, 2000, with U.S. President Bill Clinton signing a policy directive to turn off Selective Availability to provide the same accuracy to ...
L1C is a civilian-use signal, to be broadcast on the same L1 frequency (1575.42 MHz) that contains the C/A signal used by all current GPS users. L1C broadcasting started when GPS III Control Segment (OCX) Block 1 becomes operational, scheduled for 2022.
A GPS receiver in civilian automobile use. Air navigation systems usually have a moving map display and are often connected to the autopilot for en-route navigation. Cockpit-mounted GNSS receivers and glass cockpits are appearing in general aviation aircraft of all sizes, using technologies such as SBAS or DGPS to increase accuracy.
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]
Regional Military Protection (RMP) is an anti-jamming technology for military GPS consumers. RMP involves directing a massively-amplified spot beam which only includes military GPS signals over a small geographic area. US/allied military GPS receivers located within the RMP spot beam's signal footprint are significantly more difficult for ...
Israel under fire for 'GPS spoofing' affecting airplane navigation systems in Lebanon, Syria, Jordan, Egypt, Turkey and Cyprus.
During the 1990–91 Gulf War, the shortage of military GPS units caused many troops and their families to buy readily available civilian units. Selective Availability significantly impeded the U.S. military's own battlefield use of these GPS, so the military made the decision to turn it off for the duration of the war.