Tuesday, August 14, 2012

Reconciling Maps With The Real World

  We are conditioned to orientate ourselves relative to the objects in our environment and have a mental map of where things are relative to each other. We follow paths, trails and roads which take us from one place to another. But our primary sense of direction is that in which we are facing, that of forward. There are also left and right and up and down. All are determined visually. Then here are the directions north, south, east and west which are determined by the motion of the Sun and are less subject to change as we move about over larger distance scales. This is the basis for our primative sense of navigation. It is that of the naive impressionist observer and the pilot who are both focused on the real world. When specifying a course for a pilot it is best to maintain this perspective and specify the course in terms of waypoints and headings since geographic coordinates are somewhat abstracted from the real world. Survey maps are drawn to scale but treating the coordinates as plane vectors will only work correctly if by accident the scale of both directions are the same. One of the jobs of the navigator is to maintain the correspondence between a reference coordinate system and the pilot's 3D picture of his world (supported by instruments) through the points of contact that form the connection.

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