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What a rapid advancement in the technological world! We have the invention of a brilliant technology called the Global Positioning System. The usage of GPS has been made very easy, unlike the past.

GPS was first developed by the United States during the cold war, to find the location of soldiers during that war. Now, a lot of civilians have GPS technology at their disposal for different functions.Global Positioning System is a navigational system using satellite signals to fix the location of a radio receiver, on or above the earth’s surface.

GPS as a system calculate a position or coordinate on the Earth’s surface. It is of two types, which are Global satellite navigation system and Regional satellite navigation system.

Global Positioning System has quite a lot of functions in different spheres of human life, such as; agriculture, vehicle tracking, surveillance, aviation, marine, sports, military, science, telecommunications and so on.

Global Positioning System receivers are generally considered to be in three categories, they are; Low end or the recreational grade, often used for recreational purposes such as; hiking and the likes and it is less expensive and have accuracy of about 10-20 feet; Mid-Range or the mapping grade which is quite expensive for geographic information system and it has accuracy of 2-5m, sub-meter real-time, centimetre accuracy with post-processing; High end or the survey grade which is very expensive and designed for precise survey applications or sub-centimetre.

Angles are determined relative to the prime meridian and to the plain of the equator are longitude and latitude and they are measured in degrees which is shown as degrees, minutes, and seconds or expressed as decimal degrees.

If you have seen a GPS or used one before, you will see how these angles are show or expressed as decimal degree format. GPS is composed of three segments: space segment, control segment and the user segment.

Based on space segment, Global Positioning System is a constellation of at least 24 satellites. Each satellite follows one of six distinct orbits around the earth. Each circles the earth in 12 hours, that is, to ensure the satellites are visible anywhere at any time on the earth.

The Global Positioning System’s control segment consist of a global network of ground facilities that track the GPS satellite, monitor their transmissions  and send  commands and data to the constellation.

What majority are acquitted with is the user segment as it represents the application of Global Positioning System technology to everyday use. Such as; agriculture, vehicle tracking, surveillance, aviation, marine, sports and so on.

It is a clear and vivid technology and has become part of a daily technological inclined individual as such; they become Global Positioning System receivers not Global Positioning System.

Basically, Global Positioning System as a ranging system is developed with three sides, through which necessary transmission and signals must have pass through.

A Global Positioning System, specifically the user segment discovers signals from several satellites, of which the time for signal transmission is labelled with the satellite position.

In order to get satellite range, the time of transmission is compared, that is, that of arrival and when it was actually transmitted to get the difference which is multiplied with the speed of light.

Global Positioning System receivers determine the distance to satellite as a function of the amount time it takes for the satellite signals to reach the ground.

The velocity of the radio signals, like others forms of other electromagnetic radiation is known to be the speed of light. To the terminal time between transmission and reception, the receiver must be able to tell precisely between when it was transmitted and when it was received.

GPS satellite area is saddled with extremely atomic clocks, so the timing of the transmission is always known.

Looking at the idea of how a Global Positioning System locates positions on the earth surface, a GPS receiver must find the distance to three satellites of established or known positions. For instance, if the GPS receiver finds that it is 1000 miles from one satellite, the GPS receiver knows that it must be somewhere on an imaginary sphere, with the satellite as the centre and a radius of 1000 miles.

If the receiver can form these spheres for two satellites, it knows it can only be located where the surfaces of the two spheres intersect. The two spheres overlap in a ring of possible receiver positions. By generating a sphere for a third satellite, the receiver narrows its possible positions down to two points. The GPS receiver dismisses the point located in space, leaving only possible position.

Problem that mostly confronts GPS users is the inaccuracies in GPS signals. Such inaccuracies could be accounted for on the basis of orbit error, electronic “noise”, clock error, receiver error, atmospheric delay, multipath error, geometric effects and operator error.

The two methods for improving accuracy are differential Global Positioning System and Wide Area Augmentation System (WAAS). The differential Global Positioning System is the concept of making use of a determined location with a known coordinate, to make comparison with a wandering Global Positioning System receiver.

This occurs by setting up a base station on a specific determined location and the base station receiver calculate the difference between it real position and the position calculated from the satellite signals, which is then directed to the Global Positioning System receiver data. Mobile Global Positioning System stands are directed according to this differential information.

The ideas behind differential Global Positioning System, is that immediately two GPS receivers of the same location are receiving the same inaccuracies due to atmospheric delay, multipath error and so on.

Thus, the Global Positioning System base station is set up on well-known specific location that can see the amount of error being acquired by estimated correction by comparing the actual well-known position with the calculated position.

The base station can then send amendments to the mobile receiver so that the mobile receiver is recording the correct location. Wide Area Augmentation System (WAAS) does not require a receiver per se, as it is the provision of mixture of satellites in ground stations that provide GPS signal corrections. Data is collated by these stations and satellites make available corrected signals from the satellite making the location of the GPS to be accurate.

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