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5
SECTION 2
OPERATIONAL CHARACTERISTICS
This section describes the basic operational characteristics of the GPS 35LP. Additional information
regarding input and output specifications are contained in Section 4.
2.1 SELF TEST
After input power has been applied to the GPS 35LP and periodically thereafter, the unit will perform
critical self test functions and report the results over the output channel(s). The following tests will be
performed:
1) RAM check
2) FLASH memory test
3) Receiver test
4) Real-time clock test
5) Oscillator check
In addition to the results of the above tests, the GPS 35LP will report software version information.
2.2 INITIALIZATION
After the initial self test is complete, the GPS 35LP will begin the process of satellite acquisition and
tracking. The acquisition process is fully automatic and, under normal circumstances, will take
approximately 45 seconds to achieve a position fix (15 seconds if ephemeris data is known). After a
position fix has been calculated, valid position, velocity and time information will be transmitted over the
output channel(s).
Like all GPS receivers, the GPS 35LP utilizes initial data such as last stored position, date and time as
well as satellite orbital data to achieve maximum acquisition performance. If significant inaccuracy exists
in the initial data, or if the orbital data is obsolete, it may take 5.0 minutes to achieve a navigation
solution. The GPS 35LP AutolocateTM feature is capable of automatically determining a navigation
solution without intervention from the host system. However, acquisition performance can be improved if
the host system initializes the GPS 35LP following the occurrence of one or more of the following events:
1) Transportation over distances further than 1500 kilometers
2) Failure of the internal memory battery without system standby power
3) Stored date/time off by more than 30 minutes
See Section 4 for more information on initializing the GPS 35LP.
2.3 NAVIGATION
After the acquisition process is complete, the GPS 35LP will begin sending valid navigation information
over its output channels. These data include: