having read that some are uncertain about how Latitude & Longitude work {something that I was taught in Primary School}, I present this simple explanation: the Earth rotates about its axis, the Axis of Rotation, or Longitude, is also known as the Meridian; the Plane of Rotation, or Latitude, is parallel with the Equator, which is the Null point of N or S, the Poles being at 90 degrees thence. E & W are, by International Agreement, measured from the Greenwich Meridian, formerly Teneriffe, Hamburg, Paris, Beijing, or elsewhere. Grid Reference is only of use if one have a map; Navigational Astronomy gives its results in terms of Degrees, Minutes, & Seconds, Knots are the measure of Seconds of Arc traveled one hour. eg: the square root of height in Feet equals Distance seen in Knots, or Minutes of Arc. A protractor will assist one to visualise what is intended.