User's Manual

GlobalTrak ™ GT Lite Operation and Maintenance Manual
Without contact with GPS system time reference, the RTC maintains accurate time to within 3
seconds per 1 year interval. Time base shall be Coordinated Universal Time (UTC), formerly
known as Greenwich Meridian Time (GMT).
Always On/Polling Mode
Always On mode allows the GSM receiver to remain on in an idle state. This allows for
incoming SMS messages to be received be the device at any time. When an SMS is received
the main processor wakes to process the message. Incoming messages can be used to poll,
reconfigure, or send other commands or data to the device. Message types are listed in
Section XXXXXXXXXX.
GPS Receiver
The GPS receiver within GT Lite has a very high sensitivity for use in outdoors and indoors.
GPS can achieve consistent hot and warm fixes from far less than ideal scenarios such as
within a pallet on a stuffed shipping container. The GPS receiver will use a combination of
highly sensitive receiver, internal correlators, and assistance data (A-GPS) to achieve this
performance.
Time to First Fix
The GPS receiver takes no longer than 45 seconds (95%) to get a position fix from a cold
start and no longer than 10 seconds (95%) from a hot start (i.e., less than two hours since
the last fix).
Position Accuracy
The selected GPS achieves Standard Positioning Service (SPS) accuracy: 95% of position
measurements within 10 meters of the true location.
Antenna Connection Status
The antenna status is sensed, either connected or open circuit, only during the attempt for
GPS fix. If the antenna status goes from connected to disconnected, an alert is sent to the
IMB.
Assisted GPS (A-GPS)
The GPS receiver is able to use assistance data received over the GSM network to aide in
acquiring a GPS fix. This data is received from Ublox, AssistNow service.
Modes of GPS operation
There are two modes of operation for the GPS receiver: Acquisition mode and tracking mode.
They are explained below.
Acquisition mode only powers the GPS module when a fix is needed. This is typically with
every wake cycle of the GT Lite, including periodic reports and aperiodic events.
Tracking mode constantly powers the GPS module to always have a fresh fix. This mode can
be used if real time tracking is required. Tracking mode starts in acquisition mode to get the
first fix. After the first fix is complete, the GPS receiver remains powered and tracking. If the
GT Lite loses the GPS fix while in tracking mode, it will enter acquisition mode to gain a new
fix.
Prepared: R. Straz Date: July 25, 2007 Page 23 of
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