Garmin GPS 400 Pilot's Manual & Reference page 50

SECTION 2
NAV PAGES
Each satellite has a 30-second data transmission that
must be collected (hollow signal strength bar, see Figure
2-48) before the satellite may be used for navigation
(solid signal strength bar, see Figure 2-47). Once the GPS
receiver has determined the current position, the GPS 400
indicates position, track, and ground speed on the other
navigation pages. The GPS receiver status field (Figure
2-46) also displays the messages listed in Table 2-5 under
the appropriate conditions.
Message
Searching Sky
Acquiring Sat
2D Navigation
3D Navigation
Poor Coverg
Rcvr Not Usbl
AutoLocate
2-24
of the position fix, using Estimated Position Error (EPE),
Dilution of Precision (DOP), and Horizontal Uncertainty
Level (HUL) figures. DOP measures satellite geometry
quality (i.e., number of satellites received and where they
are relative to each other) on a scale from one to ten. The
lowest numbers are the best accuracy and the highest
numbers are the worst. EPE uses DOP and other factors
to calculate a horizontal position error, in feet or meters.
HUL is explained in Section 11.
Description
The GPS receiver is searching the sky for ANY visible satellites. The
pilot is informed of this status with a 'Searching the Sky' message.
The GPS receiver is acquiring satellites for navigation. In this mode,
the receiver uses satellite orbital data (collected continuously from
the satellites) and last known position to determine which satellites
should be in view.
The GPS receiver is in 2D navigation mode. Altitude data is provided
by an altitude serializer.
The GPS receiver is in 3D navigation mode and computes altitude
using satellite data.
The GPS receiver cannot acquire sufficient satellites for navigation.
The GPS receiver is unusable due to incorrect initialization or
abnormal satellite conditions. Turn the unit off and on again.
The GPS receiver is looking for any available satellite. This process
can take up to five minutes to determine a position.
Table 2-5 GPS Receiver Status Messages
GPS 400 Pilot's Guide and Reference
The Satellite Status Page also indicates the accuracy
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