Magellan GPS PROMARK X, User Manual

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Getting Started
2-14
ProMARK X
it in its memory. This means that before you obtain a position fix, the unit
already knows which satellites are scheduled to be in view (given your last
position or initial position) and where in the sky to look for them.
NOTE
The ProMARK X is shipped with an almanac. You should
therefore have no difficulty getting your first position fix once
the unit has been properly initialized.
The unit acquires almanac information in two ways: Almanac Collect and
refresh. Almanac Collect is done by using the AUX 9 function, which causes
the unit to search the sky for satellites and collect almanac data from them.
In Almanac Collect, the unit acquires a full almanac and updates the
“almanac age” date that is displayed on several of the screens.
Almanac information is refreshed while the unit is tracking satellites (getting
position fixes). If the unit is tracking satellites for 12.5 minutes or more, it
should be able to refresh the entire almanac. If the unit is tracking satellites
for only a few minutes, however, it will refresh the almanac information for
only a few satellites. Since how much of the almanac is refreshed depends
on how long the unit is tracking satellites, you may occasionally have to
collect a new almanc to be sure that the unit has up-to-date information for
the entire satellite constellation. If the unit begins to consistently take a little
longer than it should to locate satellites, it is probably time to collect a new
almanac.
In general, an almanac that is about six months of age is so far out of date,
especially if the unit has had little use since the almanac was collected. If the
unit's almanac is more than six months of age, the unit may automatically
collect a new almanac before providing positioning and navigation informa-
tion.
The only way to be certain that your almanac is completely up-to-date is to
collect an almanac with AUX 9. You should also collect a new almanac if
you are planning a data collection session, or if the almanac contains dated
information (this is likely if the almanac is one month old or more). You must
collect an almanac when the unit’s memory has been lost or cleared.
NOTE
If signal reception is good, it takes about 12-1/2 minutes to collect
a complete almanac once a satellite signal has been located.
When signal reception is poor and the unit is unable to maintain
lock on a signal, almanac collection may require 20 to 30 minutes.