To maintain the specified accuracy, most of the satellites require daily updates of their data, but some of them can receive and store corrections for several days. If no corrections are uploaded for 14 days, the positioning error on the surface will increase to 425m. After 180 days the error will be 10km. If a satellite operates without current correction data, it is called to be in extended operation . The noise code is specific for each satellite, modulating the base carrier to produce a spread-spectrum signal.
Transmission starts at the beginning of a new millisecond.
This allows to set the receiver's clock modulo 1ms. The pseudo code can be used to lock the receiver within up to 10ns, depending on the noise of the signal. When using the carrier phase, the phase in the receiver could be correlated as close as 1ps. For example, one bit stream is combined with a pseudo random number sequence that spans seven days. Fortunately most of the secrets are explained today.