Geographic Coordination Systems

Geographic coordinate systems identify every location on the Earth by a set of numbers, letters, or both.

Geographic Coordination Systems

Introduction to Geographic Coordination Systems

  • Geographic coordinate systems identify every location on the Earth by a set of numbers, letters, or both
    • Most popular is the latitude and longitude system
  • They are necessary references for fixes or other locations used in navigation
  • Different formats may be required for different flight management systems
Geographic Coordination Systems

Geographic Coordination Systems Key Highlights

  • Geographic coordinate systems provide standardized methods for identifying precise locations on the Earth’s surface.
  • Latitude and longitude are the primary coordinate references used in aviation navigation and charting.
  • Latitude measures angular distance north or south of the equator while longitude measures angular distance east or west of the prime meridian.
  • Coordinate systems support navigation, flight planning, chart creation, GPS operations, and airspace management.
  • Pilots use geographic coordinates to identify waypoints, airports, navigation fixes, and emergency locations accurately.
  • Modern GPS and RNAV systems rely heavily on geographic coordinate data for precise aircraft positioning.
  • Coordinate formats may include degrees, minutes, seconds, or decimal representations depending on navigation systems and procedures.
  • Incorrect coordinate entry or interpretation can result in navigation errors and operational hazards.
  • Understanding geographic coordinate systems improves navigation accuracy, situational awareness, and operational planning.
  • Knowledge of geographic coordination systems supports safe and efficient flight operations throughout the National Airspace System.
Geographic Coordination Systems

Latitude and Longitude

  • Lines of latitude and longitude are expressed as either degrees (°) minus (') and seconds ("), also referred to as DMS, and even further truncated to provide decimals of minutes or decimals of degrees, for example:
    • Airnav includes three lat/long formats for an airport such as KDXR:
      1. 41-22-17.5240 N 073-28-55.8820 W
      2. 41-22.292067 N 073-28.931367 W
      3. 41.3715344 N,-73.4821894 W
    • If we take the latitude reading of number 3 above (41.3715344) and multiply the decimal by 60 we get (.3715344*60) 41° 22.29206'N, which is how we get number 2 above
      • This is now the airport's lat/long expressed in degrees and decimal minutes
      • The same for longitude would be 28.931367W
    • If we take the decimals of minutes (.29206) and multiply that by 60, we get (.29206*60) 17.5236, which when rounded is how we get number 1 above
      • This is now the airport's lat/long expressed in degrees, minutes, and seconds
      • The same for longitude would be 55.8820

  • Latitude:

    • The "latitude" of a point on the Earth's surface is the angle between the equatorial plane and the straight line that passes through that point and is normal to the surface of a reference ellipsoid which approximates the shape of the Earth
    • This line passes a few kilometers away from the center of the Earth except at the poles and the equator where it passes through Earth's center
    • Lines joining points of the same latitude trace circles on the surface of the Earth called parallels, as they are parallel to the equator and to each other
    • The north pole is 90°N; the south pole is 90°S
    • The 0° parallel of latitude is designated the equator, the fundamental plane of all geographic coordinate systems
    • The equator divides the globe into Northern and Southern Hemispheres
    • One nautical mile corresponds to one minute of latitude
      • Thus, degrees of latitude are approximately 60 Nautical Miles apart

  • Longitude:

    • The "longitude" of a point on the Earth's surface is the angle east or west from a reference meridian to another meridian that passes through that point
    • All meridians are halves of great ellipses (often improperly called great circles), which converge at the north and south poles
    • A line, which was intended to pass through the Royal Observatory, Greenwich (a suburb of London, UK), was chosen as the international zero-longitude reference line, the Prime Meridian
    • Places to the east are in the eastern hemisphere, and places to the west are in the western hemisphere
    • The antipodal meridian of Greenwich is both 180°W and 180°E
    • The zero/zero point is located in the Gulf of Guinea about 625 km south of Tema, Ghana
    • In contrast to lines of latitude, lines of longitude are not a consistant distance apart, as they converge at the poles
      • Still, at the equator they are 'roughly' 60 Nautical Miles apart
  • The combination of these two components specifies the position of any location on the planet, but does not consider altitude nor depth
Geographic Coordination Systems

Geographic Coordination Systems Conclusion

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Geographic Coordination Systems

Geographic Coordination Systems References