How Satellite Navigation Works

Orienteering and satellite Navigation

Finding your way using a traditional 2D map involves determining your position by triangulation. You try and find a known landmark such as nearby mountain! And measure its angle relative to compass north. You then know by inspecting your map that you are located on that particular sight line. By finding a second landmark and again plotting its position relative to north it's possible to pinpoint your position at the intersection of the 2 sight lines. You have effectively created a triangle on a 2 dimensional map.

Global Positioning and your place at the point of a 10,000 mile tetrahedron

how satellite navigation works

GPS, (Global Positioning System), works using a similar triangulation navigation method.
In reality, the Earth is curved forming a 3-dimensional terrain so in order to 'fix' your position in space you need to make 3 readings so that your position can be located at the apex of a tetrahedron or triangular based pyramid Each edge of the pyramid wil be about 10,000 to 15,000 miles and connect you to a different satellite of known spatial position.

Navigation at the Speed of Light

GPS Navigation interprets radio signals from 3 satellites to fix your position on a pre-programmed terrain map. The receiver calculates the distance from each satellite and locates your position at the apex of a tetrahedron. A fourth satellite can be used to confirm your position and check for GPS positional errors.

Satellite Navigation Software - Complex 3-dimensional Trigonometry and a little bit of Physics

To fully triangulate your position, a GPS (Global Positioning System), receiver measures the distance from each satellite by determining the time taken to reach the GPS receiver at the speed of light (time x speed = distance) Satellite Navigation Software then factors in possible time delays caused when the radio signal slows down and gets refracted (bent) as it passes through the ionosphere and atmosphere. Effectively it's like looking at the cocktail stick in your favourite tipple. The stick appears bent at an angle yet we both know it should be straight.

International GPS

Sat Nav, or Sat-Nav, Satellite Navigation, GPS-Nav uses an internationally recognised location system.

Digitised Reference Maps of the Earth Surface

GPS, (Global Positioning System) makes use of highly complex location software and digital reference maps to help your Sat Nav Unit, (Satellite Navigation Device), to know exactly where you are, your direction of travel, speed and time to any pre-programmed destination.

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