Know where you are with GPS

 

GPS Satellite in outer space

What is GPS?

The Global Positioning System (GPS) is a satellite-based navigation and surveying system for determination of precise position and time, using radio signals from the satellites, in real-time or in post-processing mode. GPS is being used all over the world for numerous navigational and positioning applications, including navigation on land, in air and on the sea.

GPS consists of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS is a highly accurate navigation system using signals from satellites to determine a location on the Earth’s surface, irrespective of weather conditions. It is dependent on GPS satellites high above the Earth which transmits signals containing the time and location of the satellite. Any ground-based receiver which receives signals from four or more GPS satellites can use navigation equations to calculate its location on the Earth’s surface. Constant signalling can then update speed and direction information for moving receivers. GPS was originally developed for military use but since the 1990s has been open for civilian use and is now used in such common applications as mobile phones, car navigation systems, and of course surveying and mapping.

 

Other satellite systems

Other satellite navigation systems in use or various states of development include:

GLONASS – Russia's global navigation system. Fully operational worldwide.

·       Galileo – a global system being developed by the European Union and other partner countries, planned to be operational by 2014(and fully deployed by 2019)

·       BeiDou – People's Republic of China's regional system, currently limited to Asia and the West Pacific

·       COMPASS – People's Republic of China's global system, planned to be operational by 2020

·       IRNSS – India's regional navigation system, planned to be operational by 2015, covering India and Northern Indian Ocean

·       OQZSS – Japanese regional system covering Asia and Oceania

 

 

Working principle of GPS

By computing the time difference between the signal being sent and received, the 24 satellites in space determine the location of the target. GPS satellites are equipped with high precision atomic clocks. The time information is placed in the codes broadcast by the satellite so that a receiver can continuously determine the time the signal was broadcast. With information about the ranges to three satellites and the location of the satellite when the signal was sent, the receiver can compute its three-dimensional position.

 

Source:GPS Satellites in Orbit

 

Segments of GPS

The GPS consists of three segments:

1)The space segment: the GPS satellites

2) The control system, operated by the U.S. military,

 3) The user segment, which includes both military and civilian users and their GPS equipment.

 

1)The space segment

·       comprises of 29 satellites circling the earth every 12 hours at 12,000 miles in altitude.

·       is formed by a satellite constellation with enough satellites to ensure that the users will have, at least, 4 simultaneous satellites in view from any point at the Earth’s surface at any time.

 

2) The control system

·       comprises of a master control station and five monitor stations outfitted with atomic clocks that are spread around the globe.

·       also referred to as a monitor station.

 

 3) The user segment

·       comprises of the GPS receiver, which receives the signals from the GPS satellites and determines how far away it is from each satellite.

 

Using GPS for maps

Uses of GPS

GPS is very useful in:

• Marine navigation

• Airborne aviation

• Surveying of land.

• Sports such as yachting, hiking.

• The sophistication of GPS has improved so much that drivers of automobiles can get directions to their destinations easily on the screen.