intersection of two straight paths, with the transition from  one path to another being made by the aircraft using a  precisely calculated turn that flies by but does not vertically  cross the waypoint. [Figure 2-53]  Pilots typically create user-defined waypoints for use in  their own random RNAV direct navigation. They are newly  established, unpublished airspace fixes that are designated  geographic locations/positions that help provide positive  course guidance for navigation and a means of checking  progress on a flight. They may or may not be actually  plotted by the pilot on en route charts, but would normally  be communicated to ATC in terms of bearing and distance  or latitude/longitude. An example of user-defined  waypoints typically includes those generated by various  means including keyboard input, and even electronic map  mode functions used to establish waypoints with a cursor  on the display.  Another example is an offset phantom waypoint, which is  a point-in-space formed by a bearing and distance from  NAVAIDs, such as VORTACs and tactical air navigation  (TACAN) stations, using a variety of navigation systems.  When specifying unpublished waypoints in a flight plan,  they can be communicated using the frequency/bearing/  distance format or latitude and longitude, and they  automatically become compulsory reporting points unless  otherwise advised by ATC. All aircraft with latitude and  longitude navigation systems flying above FL 390 must use  latitude and longitude to define turning points.  Floating waypoints, or reporting points, represent  airspace fixes at a point in space not directly associated  with a conventional airway. In many cases, they may be  established for such purposes as ATC metering fixes,  holding points, RNAV-direct routing, gateway waypoints,  STAR origination points leaving the en route structure,  and SID terminating points joining the en route structure.  In the top example of Figure 2-54, a low altitude en route  chart depicts three floating waypoints that have been  highlighted: SCORR, FILUP, and CHOOT. Notice that  waypoints are named with five-letter identifiers that are  unique and pronounceable. Pilots must be careful of  similar waypoint names. Notice on the high altitude en  route chart excerpt in the bottom example, the similar  sounding and spelled floating waypoint named SCOOR,  rather than SCORR. This emphasizes the importance  of correctly entering waypoints into database-driven  navigation systems. One waypoint character incorrectly  entered into your navigation system could adversely affect  your flight. The SCOOR floating reporting point also is  Waypoints are predetermined geographical locations that  are defined in terms of latitude/longitude coordinates or  fixes, used to define an RNAV route or the flight path of  an aircraft employing RNAV. Waypoints may be a simple  named point in space or may be associated with existing  NAVAIDs, intersections, or fixes. A waypoint is most often  used to indicate a change in direction, speed, or altitude  along the desired path. Aviation RNAV procedures make  use of both fly-over and fly-by waypoints. A fly-over  waypoint is a waypoint that must be crossed vertically by  an aircraft. A fly-by waypoint is a waypoint that marks the  Note: While in flight, continue to verify system accuracy  by displaying bearing/range to a VOR/DME on the RNAV  system and compare it to the actual RMI reading of that  particular NAVAID.  Below is a list of generic checks that should be used when  checking the accuracy of the system prior to flight.  1. System initialization—pilots should confirm that  the navigation database is current and verify that the  aircrafts present position has been entered correctly.  2. Active flight plan check—the active flight plan  should be checked by comparing the aeronautical  charts, departure and arrival procedures, and other  applicable documents with the map display.  3. Prior to takeoff—ensure that the RNAV system is  available. If possible, check to see that the system  is updating when aircraft position is changing.  Figure 2-53. Fly-by and fly-over waypoints.  Floating Waypoints  Waypoints  User-Defined Waypoints  2-32  Fly-by waypoint  Fly-over waypoint  Alpha  Bravo  Bravo  Alpha 