Garmin G1000 Pilot's Manual page 23

The GPS Status Page provides the following information:
• Satellite constellation diagram
Satellites currently in view are shown at their respective positions on a sky view diagram. The sky view is
always in a north-up orientation, with the outer circle representing the horizon, the inner circle representing
45° above the horizon, and the center point showing the position directly overhead.
Each satellite is represented by an oval containing the Pseudo-random noise (PRN) number (i.e., satellite
identification number). Satellites whose signals are currently being used are represented by solid ovals.
• Satellite signal information status
The accuracy of the aircraft' s GPS fix is calculated using Estimated Position Uncertainty (EPU), Dilution
of Precision (DOP), and horizontal and vertical figures of merit (HFOM and VFOM). EPU is the radius of a
circle centered on an estimated horizontal position in which actual position has 95% probability of laying.
EPU is a statistical error indication and not an actual error measurement.
DOP measures satellite geometry quality (i.e., number of satellites received and where they are relative to
each other) on a range from 0.0 to 9.9, with lower numbers denoting better accuracy. HFOM and VFOM,
measures of horizontal and vertical position uncertainty, are the current 95% confidence horizontal and
vertical accuracy values reported by the GPS receiver.
The current calculated GPS position, time, altitude, ground speed, and track for the aircraft are displayed
below the satellite signal accuracy measurements.
• GPS receiver status
The GPS solution type (ACQUIRING, 2D NAV, 2D DIFF NAV, 3D NAV, 3D DIFF NAV) for the active GPS
receiver (GPS1 or GPS2) is shown in the upper right of the GPS Status Page. When the receiver is in the
process of acquiring enough satellite signals for navigation, the receiver uses satellite orbital data (collected
continuously from the satellites) and last known position to determine the satellites that should be in view.
When the receiver is in the process of acquiring a 3D navigational GPS solution, 2D NAV is indicated as the
solution since GPS altitude cannot be computed using the acquired satellite signal data. When differential
GPS (DGPS) signals are available, the solution status is indicated as 2D DIFF NAV or 3D DIFF NAV.
• RAIM Prediction
Receiver Autonomous Integrity Monitoring (RAIM) is a GPS receiver function that performs a consistency
check on all tracked satellites. RAIM ensures that the available satellite geometry allows the receiver to
calculate a position within a specified RAIM protection limit (2.0 nautical miles for oceanic and enroute, 1.0
nm for terminal, and 0.3 nm for non-precision approaches). During oceanic, enroute, and terminal phases of
flight, RAIM is available nearly 100% of the time.
The RAIM prediction function also indicates whether RAIM is available at a specified date and time. RAIM
computations predict satellite coverage within ±15 min of the specified arrival date and time.
Because of the tighter protection limit on approaches, there may be times when RAIM is not available. The
G1000 automatically monitors RAIM and warns with an alert message when it is not available. If RAIM is not
predicted to be available for the final approach course, the approach does not become active, as indicated by
the messages "Approach is not active" and "RAIM not available from FAF to MAP". If RAIM is not available
when crossing the FAF, the missed approach procedure must be flown.
190-00592-02 Rev. A Garmin G1000 Pilot's Guide for the Diamond DA40/40F
SYSTEM OVERVIEW
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