Lowrance electronic 4900M GPS Receiver User Manual


 
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4. When your adjustments are finished, return to the last page dis-
played by repeatedly pressing
EXIT.
IMPORTANT ALARM NOTES:
Anchor Alarm — The anchor alarm may be triggered even when
you're sitting still. This typically happens when using small (less
than 0.05 mile) anchor alarm ranges.
Arrival Alarm — If you set the arrival alarm's distance to a small
number and run a route (see the Navigate Routes segment), this
unit may not show navigation data to the next waypoint once you
arrive at the first waypoint. You may not be able to come close
enough to the first waypoint to trip the arrival alarm.
Auto Satellite Search
To lock onto the satellites, the GPS receiver needs to know its current
position, UTC time and date. It needs this data so it can calculate
which satellites should be in view. It then searches for only those satel-
lites. Elevation (altitude) is also used in the equation, but it's rarely
required to determine a position.
When your GPS receiver is turned on for the first time, it doesn't know
your position or elevation (altitude). It does know the current UTC time
and date since these were programmed into it at the factory and an in-
ternal clock keeps the time while the unit is turned off. (If the time
and/or date are incorrect, you can set it using the "Set Local Time" fea-
ture in the System Setup menu.)
The unit begins searching for satellites using the data it acquired the
last time it was turned on, which was probably at the factory. Since it's
almost certain that you're not at our factory, it's likely could be looking
for the wrong satellites.
If it doesn't find the satellites it's looking for after approximately one
minute, it switches to Auto Search. That's when the receiver looks for
any satellite in the sky. Due to advanced technology, the auto search
time has shrunk significantly from the early days of GPS.
Once the unit locks onto the satellites, it should take less than a minute to
find your position the next time it's turned on, provided you haven't moved
more than 100 miles from the last location it was used.