2 - NAV PAGES56Satellite 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.Vertical Navigation PageThe 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)TargetAltitudeTargetDistancePage location inNAV groupVertical SpeedDesiredTarget ReferenceVertical SpeedRequiredNOTE:To use the vertical navigation features, yourground speed must be greater than 35 knots andyou must be navigating to a direct-to destinationor using a flight plan. To create a vertical naviga-tion profile:VERTICAL NAVIGATION PROFILEVERTICAL SPEED REQUIREDDISTANCE TO TARGETTIME AND DISTANCETO PROFILETARGET ALTITUDEAND POSITIONAIRPORTCURRENT ALTITUDEAND POSITION
