Magellan GPS PROMARK X, User Manual

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Auxiliary Functions ProMARK X
4-12
ALMANAC COLLECT
AGE = 11/05/95
PRESS ENTER
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AUX 9 — Almanac Collect. In Almanac Collect, the unit collects a new
almanac from any satellite, replacing the almanac that is currently in
memory. This feature is initiated manually with AUX 9 when the unit's
almanac is at least 6 months old, or whenever you need to be sure that the
almanac is completely up to date. Almanac Collect is initiated automatically
when POS or NAV is pressed and the unit has no almanac and/or no initial
position.
Although the receiver collects updated almanac information from the
satellites it tracks, (when it is getting position fixes), the receiver must be on
and tracking satellites for at least 12.5 minutes to update the entire almanac.
Otherwise, you may not have a current almanac. If the unit's almanac is very
out of date, the receiver may not be able to locate satellites as quickly as
possible.
Generally, the Almanac Collect procedure takes about 15 minutes from start
to finish. The unit will not turn itself off during Sky Search, Almanac Collect,
or Almanac Verify, even if the Battery Saver is on.
NOTE
An almanac can be uploaded from a PC using AUX 5 and the
Post-Processing Software.
Access AUX 9. If the unit already has
an almanac, the "age" is displayed.
Age is the date that is assigned to almanac information that is broadcast from
a specific satellite on a specific day by GPS operators. Generally, age is within
six days of the actual date of collection. If the unit has no almanac, the second
line is blank.
NOTE
Since all satellites may not be operating on exactly the same
almanac cycle, almanacs collected on the same day from differ-
ent satellites may have different dates. This does not affect
almanac accuracy. When collecting data for differential process-
ing, it is sufficient if the almanacs in the units being used are
within several weeks of each other.