Garmin GPS 90 - Manual (Page 78)

Why does my GPS 90 take so long to acquire a position?
There are several variables that can effect how long the GPS 90 takes to calcu-
late a position fix. These variables can be placed into 3 categories:
• Current view of the sky
• Incorrect operating mode
• Antenna connections/internal failure
The c u rrent view of the sky d e t e rmines what satellites are ‘visible’ to the
GPS antenna. Because GPS signals are relatively low power, they do not travel
t h rough buildings or other significant stru c t u res (usually not a concern when
using your unit for flying). That means you need to give your GPS a clear view of
the sky in all directions. This is especially true when the unit is calculating an
initial fix. If you’re using the suction cup antenna, make sure the antenna has the
best view of the sky as possible. For portable use, make sure the antenna is ori-
ented in the correct position, and there are no buildings or other significant
structures to block the satellite signals. Once the GPS has determined your posi-
tion, it can usually provide accurate updates in less than ideal conditions.
Selecting the wrong operating mode can make it impossible for your GPS
to calculate a position. When the GPS 90 is powered up, it begins searching for a
set of satellites based upon the receiver’s last known position, the time of day,
and satellite almanac data stored in memory. An incorrect operating mode, inac-
curate latitude and longitude or incorrect internal clock can cause your GPS to
look for satellites that may be on the other side of the earth. Generally speaking,
the GPS 90 should be used in normal or battery saver mode unless:
• The GPS 90 is being initialized for first time use
• You’ve moved several hundred miles from the re c e i v e r ’s last known
position with the unit off
• All satellite data has been lost due to battery failure
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Appendix D
Troubleshooting
gps 90 manual 8/6/98 10:01 AM Page 70