7 Booting the GNSS receiver
If both the antenna and the power supply have been connected, the system is ready to operate. About 2 minutes
after power-up the receiver’s oscillator has warmed up and operates with the required accuracy. If the receiver
finds valid almanac and ephemeris data in its battery buffered memory and the receiver’s position has not
changed significantly since its last operation, the receiver can determine which satellites are presently in view.
Only a single satellite must be received to synchronize and generate output pulses, so synchronization can be
achieved within one minute after power-up.
If the receiver position has changed by more than one hundred kilometers since last operation, the satel-
lites’ real elevation and Doppler might not match those values expected by the receiver, and this will force the
receiver to start scanning for satellites. This mode is called
Warm Boot
because the receiver can obtain ID
numbers of existing satellites from the valid almanac. When the receiver has found four satellites in view it can
update its new position and switch to
Normal Operation
. If the almanac has been lost (because the battery
has been disconnected) the receiver has to scan for a satellite and read in the current almanac. This mode is
called
Cold Boot
. It takes 12 minutes until the new almanac is complete and the system switches to Warm Boot
mode, scanning for other satellites.
28
Date: 2nd July 2020
IMS - LANTIME M1000
