Garmin 500W Series, Pilot'S Manual & Reference

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2 - NAV PAGES
56 190-00357-00 Rev G
Each satellite has a 30-second data transmission
that must be collected (hollow signal strength bar)
before the satellite may be used for navigation (solid
signal strength bar). Once the GPS receiver has deter-
mined your position, the 500W-series unit indicates
your position, altitude, track and ground speed. The
GPS receiver status field also displays the following
messages under the appropriate conditions:
• Searching Sky —
The GPS receiver is searching the sky for ANY vis-
ible satellites. You are also informed of this status
with a “Searching the Sky” message.
• Acquiring Sat —
The GPS receiver is acquiring satellites for naviga-
tion. In this mode, the receiver uses satellite orbital
data (collected continuously from the satellites) and
last known position to determine the satellites that
should be in view.
• 3D Navigation —
The GPS receiver is in 3D navigation mode and
computes altitude using satellite data.
• 3D Differential Navigation— The GPS receiver is
in 3D navigation mode and differential corrections
are being used.
The Satellite Status Page also indicates the accu-
racy of the position fix, using Horizontal Figure of
Merit (HFOM), Vertical Figure of Merit (VFOM), and
Estimated Position Uncertainty (EPU). HFOM and
VFOM represent the 95% confidence levels in hori-
zontal and vertical accuracy. The lowest numbers are
the best accuracy and the highest numbers are worse.
EPU is the horizontal position error estimated by the
Fault Detection and Exclusion (FDE) algorithm, in feet
or meters.
NOTE Operating outside of an SBAS service area
with SBAS enabled may cause elevated EPU values to
be displayed on the satellite status page. Regardless of
the EPU value displayed, the INTEG annunciation is the
controlling indication for determining the integrity of
the GPS navigation solution.
Dead Reckoning