2 - NAV PAGES56 190-00356-00 Rev GSatellite Status Page• 3D Navigation —The GPS receiver is in 3D navigation mode andcomputes altitude using satellite data.• 3D Differential Navigation— The GPS receiver isin 3D navigation mode and differential correctionsare being used.The Satellite Status Page also indicates the accu-racy of the position fix, using Horizontal Figure ofMerit (HFOM), Vertical Figure of Merit (VFOM), andEstimated Position Uncertainty (EPU). HFOM andVFOM represent the 95% confidence levels in hori-zontal and vertical accuracy. The lowest numbers arethe best accuracy and the highest numbers are worse.EPU is the horizontal position error estimated by theFault Detection and Exclusion (FDE) algorithm, in feetor meters.NOTE Operating outside of an SBAS servicearea with SBAS enabled may cause elevated EPUvalues to be displayed on the satellite statuspage. Regardless of the EPU value displayed, theINTEG annunciation is the controlling indicationfor determining the integrity of the GPS naviga-tion solution.Vertical Navigation PageWARNING: VNAV is to be used for advisorypurposes only. VNAV messages or vertical speedrequired should not be used to maintain terrainor ATC clearances. Terrain and ATC clearances arethe sole responsibility of the pilot.The 400W-series vertical navigation page (the lastNAV page) allows you to create a three-dimensionalprofile which guides you from your present positionand altitude to a final (target) altitude at a specifiedlocation. This is helpful when you’d like to descendto a certain altitude near an airport. Once the profileis defined, message alerts and additional data on thedefault NAV and map pages will keep you informed ofyour progress.Altitude Reference(AGL or MSL)TargetAltitude TargetDistancePage location inNAV groupVertical SpeedDesiredTarget ReferenceVertical SpeedRequiredVNAV is inhibited in the following conditions:• Groundspeed is less than 35 knots• No active flight plan or direct-to destination• SUSP mode• Vectors-to-Final mode• VLOC mode• After the FAF on an approach
