GPS satellites transmit two types of radio signals: C/A-code and P-code.
Briefly, here are the uses and differences of these two types of signals.
Coarse Acquisition (C/A-code)
Coarse Acquisition (C/A-code) is the type of signal that consumer GPS units receive. C/A-code is sent on the L1 band at a frequency of 1575.42 MHz. C/A broadcasts are known as the Standard Positioning Service (SPS). C/A-code is less accurate than P-code (see the following section) and is easier for U.S. military forces to jam and spoof (broadcast false signals to make a receiver think it’s somewhere else when it’s really not). The advantage of C/A-code is that it’s quicker to use for acquiring satellites and getting an initial position fix. Some military P-code receivers first track on the C/A-code and then switch over to P-code.
Precision (P-code)
P-code provides highly precise location information. P-code is difficult to jam and spoof. The U.S. military is the primary user of P-code transmissions, and it uses an encrypted form of the data (Y-code) so only special receivers can access the information. The P-code signal is broadcast on the L2 band at 1227.6 MHz.
P-code broadcasts are known as the Precise Positioning Service (PPS).
Briefly, here are the uses and differences of these two types of signals.
Coarse Acquisition (C/A-code)
Coarse Acquisition (C/A-code) is the type of signal that consumer GPS units receive. C/A-code is sent on the L1 band at a frequency of 1575.42 MHz. C/A broadcasts are known as the Standard Positioning Service (SPS). C/A-code is less accurate than P-code (see the following section) and is easier for U.S. military forces to jam and spoof (broadcast false signals to make a receiver think it’s somewhere else when it’s really not). The advantage of C/A-code is that it’s quicker to use for acquiring satellites and getting an initial position fix. Some military P-code receivers first track on the C/A-code and then switch over to P-code.
Precision (P-code)
P-code provides highly precise location information. P-code is difficult to jam and spoof. The U.S. military is the primary user of P-code transmissions, and it uses an encrypted form of the data (Y-code) so only special receivers can access the information. The P-code signal is broadcast on the L2 band at 1227.6 MHz.
P-code broadcasts are known as the Precise Positioning Service (PPS).
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