Garmin GTN 650 Pilot's Guide - Page 324

Note 1: Foreword Getting Started Xpdr Ctrl Com/Nav FPL Direct-To Proc Wpt Info Map Traffic Terrain Weather Nearest Music Utilities System Messages Symbols Appendix Index 16-18 There are several reference datums that waypoints can be surveyed against. TSO-C146 normally requires that all waypoints be referenced to the WGS84 datum, but allows for navigation to waypoints that are not referenced to the WGS84 datum so long as the pilot is notified. Certain waypoints in the navigation database are not referenced to the WGS84 datum, or their reference datum is unknown. If this is the case, this message is displayed. Garmin cannot determine exactly how close the non-WGS84 referenced waypoint will be to the WGS84 datum that the GTN uses. Typically, the distance is within two nautical miles. The majority of non-WGS84 waypoints are located outside of the United States. Garmin GTN 625/635/650 Pilot's Guide 190-01004-03 Rev. B