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L1C is a civilian-use signal, broadcast on the L1 frequency (1575.42 MHz), which contains the C/A signal used by all current GPS users. The L1C signals broadcast from GPS III and later satellites, the first of which was launched in December 2018. [1]
The Global Positioning System carriers are in the L band, centered at 1176.45 MHz (L5), 1227.60 MHz (L2), 1381.05 MHz (L3), and 1575.42 MHz (L1) frequencies. L band waves are used for GPS units because they are able to penetrate clouds, fog, rain, storms, and vegetation.
Demodulating and Decoding GPS Satellite Signals using the Coarse/Acquisition Gold code. Because all of the satellite signals are modulated onto the same L1 carrier frequency, the signals must be separated after demodulation. This is done by assigning each satellite a unique binary sequence known as a Gold code. The signals are decoded after ...
GPS signals can also be affected by multipath issues, where the radio signals reflect off surrounding terrain; buildings, canyon walls, hard ground, etc. These delayed signals cause measurement errors that are different for each type of GPS signal due to its dependency on the wavelength. [4]
One of the first announcements was the addition of a new civilian-use signal to be transmitted on a frequency other than the L1 frequency used for the existing GPS Coarse Acquisition (C/A) signal. Ultimately, this became known as the L2C signal because it is broadcast on the L2 frequency (1227.6 MHz).
A GPS disciplined oscillator unit with a GPS antenna input, 10 MHz and 1 pulse-per-second (PPS) outputs, and an RS-232 interface.. A GPS clock, or GPS disciplined oscillator (GPSDO), is a combination of a GPS receiver and a high-quality, stable oscillator such as a quartz or rubidium oscillator whose output is controlled to agree with the signals broadcast by GPS or other GNSS satellites.
The GPS alternatives rely on signals that can be measured locally (for instance, motion or magnetic fields as used in a compass), so a vessel can navigate even when GPS is unavailable or untrusted.
These units use the signal from both the L1 and L2 GPS frequencies. Even though the L2 code data are encrypted , the signal's carrier wave enables correction of some ionospheric errors . These dual-frequency GPS receivers typically cost US$10,000 or more, but can have positioning errors on the order of one centimetre or less when used in ...