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Geocaching NSW: How GPS works

History of GPS

GPS consists of a series of satellites, called NAVSTAR (navigation satellite timing and ranging) and a ground based GPS receiver. The NAVSTAR satellites orbit the Earth at a distance of approximately 19 000 kilometres and take 12 hours to complete an orbit of the Earth. The GPS receiver determines its location on the Earth's surface by collecting signals from the orbiting GPS satellites.

Read more: History of GPS

Degree and minutes

Many years ago, cartographers (map makers) knew that the world was a sphere. To help people figure out where they were located on this sphere, they devised a grid system called longitude and latitude.

The Earth rotates once every 24 hours around its axis. The points where this axis meets the surface are called the North and South Poles. Half way between the North and South Pole is an imaginary line that runs around the Earth called the equator.

Read more: Degree and minutes

GPS in research

The GPS is used quite extensively in the commercial sector by trucking and freight corporations to monitor shipments of goods and plan routes to deliver shipments faster and more efficiently.

Some cars have GPS on-board navigation to assist drivers in finding their way through a busy city or to locate their car if it has been stolen. Similarly, the GPS units in Queensland trains provide passengers with information about where the trains are and when they will arrive.

Read more: GPS in research

Finding your location

Even though a grid system had been developed, it was still difficult to determine the exact latitude or longitude of your location. Some people used the position of stars, while others matched the position of the Sun with accurate timepieces.

Today, the satellite-based GPS allows anyone with a receiver to find their longitude and latitude quickly and easily.

The receiver uses signals from the US NAVSTAR satellites to triangulate its location.

Read more: Finding your location