AUXILIARY AVIATION TRAINING MANUAL(65)

 
G.3.  Long-Range Aid to Navigation
 LORAN receiver uses a network of land-based radio transmitters.  Before it can provide accurate navigational information, it must acquire signals from three or more stations.  Most LORAN computers will display the aircraft’s position in latitude/longitude coordinates that the flight crew must be able to understand.  Many LORAN units have the capability to store a number of positions as waypoints and may display range and bearing, ground speed, cross-track error, and other information relative to these waypoints and to the aircraft’s position.  LORAN does not depend on line of sight signals.  Special aviation LORAN units may contain databases that permit recall of information about airports and other navigation waypoints.
 
G.4.  Global Positioning System
 GPS depends on information received from satellites.  The GPS computer displays the aircraft’s position in latitude/longitude, and may also provide altitude information.  The information available to the pilot is much the same as that given by LORAN, including ground speed, cross-track error, and relative positioning to various waypoints.  The GPS units may also contain databases providing information about airports and navigational aids, and permitting flights to be planned and flown directly between data points.  Some of the GPS units are equipped with “moving maps” which constantly update and show the position of the aircraft.  (see paragraph G.5.b of this chapter for proper GPS display)
 
G.5.  Use of Navigation Equipment for SAR
 The following information applies when using the VOR system or LORAN/GPS navigation equipment for SAR missions:
 
G.5.a.  VOR System
 The VOR system is basically line of sight which increases the aircraft’s effective range with altitude.  The effective range for the VOR portion (azimuth) is greater than that for the DME (range).  Either lines of position (radials) from two VOR stations or one line of position and distance from a VORTAC or VOR/DME station may determine a position fix.  This information is then plotted on an aeronautical chart and converted to latitude/longitude, if required.
 
G.5.b.  LORAN/GPS
 A position determined by a LORAN or GPS navigation computer is normally displayed in latitude and longitude and may be passed directly to a vessel or shore station with no correction, adjustment, or other processing necessary.  It is necessary to ensure that the characteristics of the unit and display properties are properly set or understood, so that it is clear whether the unit is displaying nautical or statute miles, and whether the bearings are magnetic or true.  When flying over a significant target, the position may be entered as a waypoint.  Recalling this waypoint will display the position and the LORAN or GPS will provide navigation directions relative to that position.  Returning to the position, vectoring a surface craft to the position, or orienting a search about the position becomes an exercise in reading and interpreting the display.
　
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