Selective availability (accuracy in GPS positioning)
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L-2 SIGNAL
The second L-band signal of the GPS satellite, transmitted at 1227.60 MHz, modulated with the P-code and navigation message.
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L-1 SIGNAL
The primary L-band signal transmitted by each GPS satellite at 1572.42 MHz. It is modulate
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ANCHOR WATCH
The crewmen assigned to take care of the ship while anchored or moored, charged with such duties as making sure that the anchor is holding and the vessel is not drifting. Most marine GPS units have an Anchor Watch alarm capability.
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GPS
Global Positioning System (see GNSS)
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GPS
Global (satellite) positioning system
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P-CODE
The precise code of the GPS signal, used by military receivers.
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PSEUDO-RANGE
Measure of distance from GPS satellite to receiver, uncorrected for synchronization errors between satellite and receiver clocks.
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PSEUDO-RANDOM NOISE
An apparently random but reproducible sequence of binary code used in the GPS signal.
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SELECTIVE AVAILABILITY
A Department of Defense program which degrades the accuracy of the pseudorange measurement of the GPS signal by dithering the clock time and ephemerides data, providing a less accurate fix for civilian users. It can be turned on or off at will by DoD.
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C/A
Coarse Acquisition - the radio signal on the L band frequency of 1575.42 MHz that civilian GPS receivers use. As opposed to the P code used by the US military.
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