Useful Information
Parallels: Circles parallel to the equator, ranging from 0° to 90° N or S. Only the equator is a great circle.
Meridians: half-Circles conversing at the poles, ranging from 0° to 180° E or W. Each pair of meridians forms a great circle.
Prime Meridian: 0° or the Greenwich meridian which divides the Western and Eastern hemispheres.
Great Circle: The intersection of a sphere and a plane through its center.
Small Circle: The intersection of a sphere that does not pass though its center.
Time Zones: By convention 24 zones, each 15° longitude wide. Hence, noon at greenwich gives midnight at 180° E.
GMT: Greenwich Mean Time or UTC or Zulu, and is the time in Greenwich. Antonym: Local time. Berlin's local time = GMT + 1.
Date Line: The meridian which extents from the prime meridian. Here, not only the hour changes, but also the date.
Latitude: Position property defined by the number of degrees North or South of the equator, varies from 0° to 90°.
Longitude: Position property defined by the number of degrees East or West of the prime meridian, varies from 0° to 180°.
Position: Latitudes first and Longitudes second. For example: Nijmegen (NED) = 51° 50',1 N , 05° 52',0 E.
Nautical Mile: One nm is one minute (') on the chart. 1' equals 1.852 meters.
Knots: Nautical miles per hour.