GPS6000-LITE - GPS Time Receiver - User Manual - Version 1.2
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3 - System operation
Operation of the GPS6000-LITE is fully automatic. The following
theory of operation is supplied as a reference, to allow the user to gain
a basic understanding of the technology used in the GPS6000-LITE.
3.1 - Theory of operation
When first powered-up, the GPS6000-LITE initiates a cold start
search acquisition process. GPS Satellites are tracked and an initial
location/timing solution is computed. Typically, the search acquisition
process will complete within one minute.
After the search process has been successfully completed, the
GPS6000-LITE begins downloading GPS almanac data
(containing
orbit and status reference information for each satellite vehicle, along
with UTC offset data)
. The GPS6000-LITE must continuously track
the GPS satellites for around 15 minutes to download a complete
almanac.
Once the almanac download is complete, the GPS6000-LITE begins
transmitting time data and enters self-survey mode. In self-survey
mode, the GPS6000-LITE computes a highly accurate reference
location by averaging multiple position fixes.
After a successful self-survey has completed
(approximately 35
minutes of uninterrupted GPS tracking)
, the computed reference
location is stored and the GPS6000-LITE moves to high-accuracy
timing mode. In this mode, the GPS6000-LITE is able to provide time
data accurate to within 30 nsec of UTC.
Note that if your GPS6000-LITE has previously performed a full
self-survey and the location has not changed, a new self-survey will
not be performed. The GPS6000-LITE will move directly from almanac
download to high-accuracy timing mode. If the GPS6000-LITE has
previously performed a full self-survey and the location has changed,
a new self-survey will be performed.
3.2 - Operation in non-static applications
The GPS6000-LITE is optimised for use in static installations. In
normal operation, the GPS6000-LITE performs a self-survey then
switches to high-accuracy timing mode
(where the system corrects
only for clock errors)
. In this mode, the GPS6000-LITE assumes the
location does not change.
It is possible to use the GPS6000-LITE in non-static applications.
However, the system will not operate in high-accuracy timing mode
and timing accuracy will be degraded.
