Description Global Positioning System GPS Computer Science

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Description- Global Positioning System (GPS) is a satellite navigation system which allows the user geographically to obtain latitude, longitude, and altitude of their position. It was created and is still controlled by the US Department of Defence in the 1970's and is supported by the Military and its satellite named 'Navstars'. Ever since the date of invention, additional satellites were launched into space which provided the GPS advanced information and navigation. The design of satellites had been the same but the operation system had been changed and had become more advanced like the controls of the system and accurate information [SNAP Australia, 1999]. The US Government allowed all societies and civilians to use the GPS in 1996. Societies have been affected ever since the decision of the Government by the Global Positioning System since it provides safer and reliable ways for travel especially in the Ship and Aircraft society, aids in the development of societies as it provides faster, inexpensive and precise construction particularly in the Construction society, provides people with driving directions to destinations mainly for all civilians, and as well, GPS affects individual soldiers in the Defence department since it provides increased chances of hitting the choice of target while in battlefields. [Knol Beta 2008]

Properties- The Global Positioning System consists of three physical principles which make the system work. One of the physical principles is the the GPS satellites which consists of 24 satellites, it is a man-made device that orbits the earth twice a day; it sends position information to earth, each carrying accurate 'atomic clocks'. Another physical principle is the GPS ground station which is located on the earth's surface, they are used in the operation to update geographical information and control the satellites. Another physical principle is the GPS receiver which is an electronic device used on earth that receives the position information from the satellites to find its location in a form of latitude, longitude, and altitude. All these physical principles interact together to make the operation of the GPS work. As GPS satellites orbit the earth twice a day they send radio signals (frequencies between 390- 1575.42MHz) to the GPS receivers. The GPS receiver compares the time of the signals that was sent from the satellites and the time the signals was received from the satellites using its 'atomic clock'. This then calculates the distance of the satellite to the GPS receiver. Using the distance measurements, the GPS receiver's position is then found and is shown on the electronic map. When the GPS receiver is linked to the GPS satellites, the 'triangulation' process is formed to get the GPS receivers position. In the 'triangulation' process the satellite transmits the signals into three spherical waves to receive a 2D position and the track movement in the form of longitude and latitude. The spherical wave then spreads out to reach the earth's surface and then forms the point of intersection from the three waves. The point of intersection then determines position of the receiving device. Using four satellites in the 'triangulation' process gives the 3D position. As there are radio waves used in the signals, there are different types of signal types of different frequencies and different uses. Civilians GPS users have a receiver using "L1 signals" with the frequency of 1575.42MHz and Military GPS users have a receiver using "L2 signals" with the frequency of 1227.6 MHz [Rare Niche Web Sites, 2011].

= Radio Signal path

Research- There is some current research being done in connection with the Global Positioning System for the future. Some research being done currently to improve the reception and more advanced information include new satellites and ground stations with more powerful and effective radio signals used in the operation of the GPS. New devices like handheld GPS will have advanced features and applications like improved maps and directions. As there is inaccurate signals from the GPS satellites, research have been done to improve the signals accuracy [SNAP Australia, 1999].

2. Television

Description- Television is a telecommunicating type of media that transmits and receives moving images in the form of grey- scale or color and is supported with sound. It was available since the late 1920's in homes, and business etc. and it is categorized as a type of entertainment and receiving information like news. Radio waves are involved in the transfer of energy to television. This type of electromagnetic wave is used to broadcast television programs. Radio waves that are used for television have a long wavelength of 1 mile or more, therefore the signals carries a lot of information [Michael Anissimov, 2011].

Properties- The main properties that make television work is the antennae which is used for the reception of broadcasting channels with transmitted frequencies up to 250 MHz in VHF type (very high frequency) and in the UHF type (Ultra-high frequencies) transmitting frequencies up to 960 MHz which is only used for broadcasted channels from other countries. The TV antennae receive the signal in the form of radio waves and are broadcasted onto the television screen. Another property that makes television work is the television set which is the device that shows the images that are being broadcasted. An added property to television is the television station which is an organization that transmits the broadcasting programs to each of the television antenna in each home. The television station broadcasts its programs through tall radio tower. VHF stations have tall antennae's as they have long wavelengths and require less power. UHF stations have a short antennae's as they have short wavelengths but with high power. There are channels that are broadcasted from other countries as they require a television satellite which they receive the signals from the television station in the country and is transmitted to the television station to another television station. The signals are then received from home through a satellite dish which is placed on house roofs [Vaughnlea Leonard, 2009].

= Satellite Television Signal Path= Local/ same country Television Signal path

3. Radio Wave

Description- Radio wave signals are broadcasted through Amplitude Modulation (AM) and Frequency Modulation (FM). Modulation is a process of when the amplitude or the frequency is changed in a wave having the purpose of adding a signal. When the radio wave is modulated, the amplitude or the frequency of the wave is changed if the information is being transmitted through the AM or FM band. In AM radio, when the strength of the signal is changed to a way that links to the information being broadcasted, it occurs when the signal is added to the AM signal radio wave. As the signal is added to the wave, the amplitude of the wave is changed but the frequency is remained the same; this is called modulation of the amplitude. When amplitude is affected by modulation, the wave is converted by a radio receiver to produce sound. In FM radio, the frequency of the radio wave is changed as there is a signal added to the wave which is being transmitted. This process is called FM radio transmission. During the transmission as the wave is transmitted to the radio receiver, sound is produced as the receiver removes the changed modulation and keeps the amplitude that has remained the same. When AM and FM produce sound after the process of modulation, it is then known as AM and FM broadcasting. FM broadcasting is much popular than AM broadcasting since FM give less 'noise' than AM. FM radio gives less 'noise' because it only relies on the frequency changes rather than strength of the signal that is received by the radio receiver (which occurs in AM) so it is much dependent for music noise. But, FM signals can be interfered in many ways (e.g. interfered by construction or buildings) since amplitude is not modulated or changed; AM signals has long distance and is much wider in the atmosphere [Michael Andriessen 2004].

Properties- The main properties needed to broadcast Radio waves are the transmitter and its antenna, the transformer, and the radio receiver. Electrical signals that travel up and down the antenna wire is sent from the transformer. These electrical signals produce Radio waves. In this stage, no information or signals have been determined and as well the radio wave is the carrier wave. The information or signals are determined in the carrier wave (radio wave) by the transformer. The strength of the radio wave's amplitude or frequency of the sound signals that are required to be transmitted is changed or modulated by the transformer. Changing or modulating the strength of radio wave's amplitude is called AM and changing or modulating the strength of the radio wave's frequency if called FM. The radio receiver's antenna receives the radio wave which is transmitted from the transmitter's antenna; while this is occurring, the frequency or the amplitude of the radio wave being transmitted to the antenna is being changed or modulated to suit the power of the radio speakers. This purpose of this process is to produce decent reception [Michael Andriessen 2004].

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