Thesis | Graduate and Postdoctoral Studies - McGill University

The motivation for GPL-GPS is the desire for advanced features in an inexpensive receiver

Essay On Gps Gps Term Paper Read a description of GPS

A land surveyor for instance may need sub-centimetre level measurements while a recreational boater would only need positions accurate two under 20 metres to find out the best possible route to a previous marked good fishing area. Although each user has various uses for GPS the receiver is the basic element of the user segment and they all work on similar principles. This chapter contains a basic run though about how a GPS works.

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Thesis Statement on GPS | Category: English

2.0 THE THREE SEGMENTS OF GPS
GPS is a system of Satellites surrounding the earth. It is used to obtain accurate three-dimensional positions on the earth’s surface. GPS can be divided into three separate segments; the user, space, and control segment. The user segment is made up of those who use GPS and the receivers they use. They consist of the military users, land surveyors, recreational users, and many more. The satellites orbiting around the earth make up the space segment. Thirdly, the control segment is the five monitor stations located around the world.
This chapter will then take a look at the three segments of GPS. The user, space, and control segments can be found in section 2.1, 2.2, and 2.3 respectively.

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2.3 The Control Segment
The stations located at various positions around the globe make up what is called the control segment. Their purpose is to monitor and maintain the space segment constantly. Since the United States created GPS for their use the DoD is what makes up the control segment.

GPS PSEUDOLITES: THEORY, DESIGN, AND APPLICATIONS


In a nutshell, GPS is based on satellite ranging - calculating the distances betweenthe receiver and the position of 3 or more satellites (4 or more if elevation is desired)and then applying some good old mathematics. Assuming the positions of the satellites areknown, the location of the receiver can be calculated by determining the distance fromeach of the satellites to the receiver. GPS takes these 3 or more known references andmeasured distances and "triangulates" an additional position. In order for the user segment to obtain an accurate GPS position the user segment must be able to determine the exact position of the satellite in space. Determining the location of a satellite that orbits around the earth at an average of 20,183 kilometres above the earth is another matter altogether [Logsdon, 1992]. The fact that the satellites are actually that high above the earth is a benefit. They are high enough that they are well clear of the earth’s atmosphere so their orbit is easily predicted with a large accuracy. To ensure near perfection the control segment constantly monitors the satellites to make sure that they are following their orbit. As the satellites orbit over one of the control stations, the control segment precisely measures their altitude, position, and speed for any variations called ‘ephemeris’ errors. The errors are usually minor and are caused by such things as pressure of solar radiation and gravitational pull from the sun and moon. As stated in section 2.3 the atomic clocks time tends to drift slightly. Instead of constantly correcting the atomic clocks of each satellite their time is constantly monitored by the control segment and their error is transmitted to the receiver on earth, this is known as the broadcast clock correction. Both the ephemeris and timing errors are then sent up to the satellite, which in turn broadcasts these minor corrections to the user segment.While affirming its commitment towards making attractive cash returns, GAP has recently announced a share repurchase plan, and it has also raised its quarterly dividend. I believe the company's strong strategic initiatives will continue to improve its cash flow base in order to help GPS sustain the stock's key attractiveness by making hefty cash returns in the years ahead.The analysis and discussion of Global Positioning System concepts has revealed that GPS technology is a force in the force. Perhaps the system designers had different intentions when developing and designing GPS technologies but these applications have added to the versatility of usage of GPS not only as a system for estimating the precise positioning of objects but also in the provision of accurate and reliable navigation information. Irrespective of time, location, and whether, Global Position System provides unparalleled range of services to commercial military and consumer applications. Majority of these services enables airborne, land, and sea users to know their exact velocity, location, and time whenever and wherever on Earth. Indeed, the GPS technology supports numerous positioning and navigation applications that satisfy a multitude of user needs. At this moment, the widespread usage of GPS applications in different sectors of the economy makes it exceedingly difficult to think of a life without Global Positioning Systems. It is evident that creating a complex system such as the GPS technology is not an easy task and this can be proven from the few competitors of GPS technology. GPS technologies and systems are used in different sectors of society. This includes road and rail transportation, marine navigation, agriculture, the airline industry, space science, recreation, military, and in the provision of public safety among others. Information and signals relayed by GPS systems are safe and reliable thereby making GPS technology the ideal navigation and positioning equipment.CHAPTER 3
SUMMARY
The Global Positioning system can be broken down into three separate categories. They comprise of the user, space, and control segment. The user segment is made up of all those who use GPS and the receivers they use. The kinds of receivers vary as much as the different kinds of users but all receivers work on basically the same principles.An effective way to reduce the effect of errors inherent to GPS is the relative positioning. The principle is to simultaneously collect observations to a receiver located at a reference station whose coordinates are known. The distance measurements are compared with theoretical distances calculated from the known coordinates of the station and satellites. These differences represent the distance measurement errors and are calculated for each satellite at each epoch. Subsequently, these differences become distance correction terms (also called differential corrections) that are applied to distance measurements collected by the rover. In this way, errors common observations of the reference station and rover are eliminated. Errors are more similar when the 2 receptors are more frequent.