L04_6P PDF - Geographic Coordinate System

. Geographic coordinate system • Created by drawing imaginary lines on the earth’s surface. • Used for specifying coordinates to aid navigation . Latitude lines • Latitude lines are imaginary horizontal lines on the earth’s surface. Each latitude line is a circle. There are 180 degrees of latitu...

. Geographic coordinate system • Created by drawing imaginary lines on the earth’s surface. • Used for specifying coordinates to aid navigation . Latitude lines • Latitude lines are imaginary horizontal lines on the earth’s surface. Each latitude line is a circle. There are 180 degrees of latitude and 0° line is also known as the Equator http://www.mrdowling.com/601-grid.html . Longitude Lines • Longitude lines are imaginary vertical lines on the earth’s surface. They are also known as meridians. • Each meridian is a semi circle. There are 360 degrees of longitude and 0° line of longitude is also known as the Prime Meridian. http://www.mrdowling.com/601-grid.html . Geographical Coordinates - Interpretation • E.g. 4512N 06023E or N4512 E06023 is read as: (Latitude) (Longitude) (Latitude) (Longitude) 45 degrees 12 minutes North, 60 degrees 23 minutes East 4512N 06023E . Geographical Coordinates - Antipodes • A location that lies diametrically opposite of any location on earth is called an antipode. • Determining the coordinates of an antipode. e.g. what is the antipode of 01°22’S, 103°48’ E? Antipode latitude number is the same, only the sign is inverted i.e. 01°22’S is inverted to 01°22’N Antipode longitude calculation: 103°48’E – 180° = 103°48’ – 179°60’ = –76°12’E which the same as 76°12’W. The antipode of 01°22’S, 103°48’ E is 01°22’N, 76°12’W . Map projections • A map is a two-dimensional representation of a threedimensional earth. The types of map projections are: Cylindrical Conic Planar E.g. Mercator Projection E.g. Lambert Conformal Projection E.g. Azimuthal Projection . Mercator projection • The most common type of cylindrical projection where the cylinder tangent is at the equator • Direction is preserved in all locations on the map. • Size distortion increases as we go further away from the Equator. • E.g. Greenland appears larger than Africa on a Mercator projection map, but Africa is 14 times larger than Greenland. . Great Circle • A great circle is the largest circle that can be drawn on the surface of a sphere. The centre of the circle coincides with the centre of the sphere. • The equator and all longitude lines lie on great circles. • A great circle track is the shortest distance between 2 points on earth and it lies on the shorter arc of a great circle. . Rhumb line • A rhumb line is a line that cuts all longitude lines at the same angle. Although it appears as a straight line on a Mercator projection map: D A B C • It is actually a curved path on the surface of the earth: . Rhumb line track • To follow a rhumb line track, pilots just need to fly the same magnetic heading throughout which is convenient. • However it is not the shortest path between 2 locations on earth.