Custom «Global Positioning System» Essay Paper

The Global Positioning System (GPS) is a satellite-based steering system that comprises a set-up of 24 satellites placed into the path by the U.S. Defense forces. The Global Positioning System was projected initially for military applications, although in the 1980s, the government permitted civilian use of the system. Notably, GPS works in any environment, wherever in the world, 24 hours on a daily basis. There are no payments or setup charges to exploit GPS, as it is free of charge. The GPS program provides significant capabilities to martial, communal as well as commercial users all over the world. Additionally, GPS is the strength of character for modernizing the universal air traffic system. Changes in technology and recent demands in the current system have resulted to efforts to modernize the GPS system and come up with the new generation of GPS III satellites with Next Generation Operational Control System. This essay discuses the functions, advantages and disadvantages of Global Positioning System in detail.

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Working of the Global Positioning System

GPS satellites go round the earth twice a day in a fixed orbit and broadcast signal information to earth. GPS receivers obtain this information then utilize triangulation to gauge the user's exact location. Fundamentally, the GPS receiver system contrasts the exact time a signal was transmitted by a satellite with the exact time it was received (Diggelen 55). The difference in time tells the GPS receiver how distant the satellite is. Now, with distance dimensions from additional satellites, the receiver is able to establish the user's location and exhibit it on the unit's electronic chart. A GPS receiver should be locked on to the signal of not less than three satellites to work out a 2D location (latitude and longitude) and path movement. With at least four or additional satellites in view, the receiver can resolve the user's 3D location (altitude, longitude and latitude). Once the user's location has been found, the GPS unit is able to analyze additional information, such as velocity, bearing, path, trip distance, distance to destination, dawn and dusk time and more.

The Global Positioning System Accuracy

The current GPS receivers are exceptionally perfect, appreciation to their similar multi-channel make. Garmin's 12 similar channel receivers are rapid to lock onto satellites systems when primary turned on, and they uphold tough locks, even in thick plants or urban settings that have tall buildings. Such distinctive factors and further sources of blunder can influence the precision of GPS receivers. Garmin GPS receivers are usually accurate to around 15 meters on standard. Latest Garmin GPS receivers that have Wide Area Argumentation System capability are able to advance accuracy to not more than three meters normality (Farrell 35). Additionally, no supplementary apparatus or bills are mandatory to take advantage of WAAS. Users are able to get improved precision with Differential GPS (DGPS), which improves GPS signals to around a standard of three to five meters. The U.S. Coast Guard works with the most familiar DGPS correction service. This system comprises of a set-up of towers that obtain GPS signals and broadcast an improved signal by beacon transmitters.

Global Positioning System Restriction on Civilian Use

Some countries such as the US have restriction on civilian use. All GPS receivers with the capability of functioning over 18 kilometer-altitude, as well as 515 meters for every second are classified as munitions (weapons) for which governmental export licenses are compulsory (McNamara 65). These restrictions attempt to avert use of system receivers in a ballistic rocket. They would not thwart use in a cruise rocket since their altitudes and velocities are comparable to those of common aircraft.

The Global Positioning System Signal

GPS satellites broadcast two stumpy power radio signals, marked L1 and L2. Particularly, the resident GPS makes use of the L1 frequency of 1575.42 MHz in the available UHF band. The signals move by a stripe of view, meaning they will go by through clouds, glass as well as plastic although will not go through many solid substances like buildings and mountains. A GPS signal usually comprises three dissimilar types of information - a pseudorandom code, ephemeris statistics and almanac statistics (Samama 77). The pseudorandom code is an identification code that recognizes which satellite is broadcasting information. Ephemeris statistics, which are continuously broadcast by every satellite, have vital information concerning the condition of the satellite (healthy or unhealthy), present date and time. This piece of the signal is necessary for determining a location. The almanac statistics notify the GPS receiver where every GPS satellite must be at any time during the day. To sum that up, each satellite broadcasts almanac statistics showing the orbital information for that satellite and for each extra satellite in the structure.

The Sources of Errors in the Global Positioning System

Several factors can mortify the GPS signal and therefore, influence accuracy.

Firstly, there are the ionosphere and troposphere delays. The satellite signal slows while it goes through the air. The Global Positioning System makes use of a fitted model that analyzes a regular amount of delay to partly accurate for this sort of blunder.

Secondly, signal multipath. This happens when the GPS signal is replicated off substances such as sky scrapers or huge rock surfaces before it arrives at the receiver. This adds the travel time of the signal, thus results to errors.

Thirdly, the receiver clock error is also another factor that influence the accuracy of GPS. A receiver's fitted clock is not as perfect as the minute clocks aboard the GPS satellites. Consequently, it may have extremely slight timing blunders.

Additionally, there are orbital errors. These are also identified as ephemeris errors, these are imprecision’s of the satellite's reported site.

Moreover, there is the number of satellites visible (Xu 86). The more the satellites a GPS receiver can detect, the better the accuracy. Structures, topography, electronic interference, and sometimes thick foliage, can obstruct signal reception, causing location blunders or perhaps no location reading at all. GPS units naturally will not perform indoors, underwater or subversive.

The satellite geometry/shading is another factor. This refers to the virtual location of the satellites at whichever given time. Perfect satellite geometry exists whilst the satellites are positioned at extensive angles relative to each other. Poor geometry occurs once the satellites are positioned in a row or in a firm grouping.

Lastly, there is the intentional degradation of the satellite signal. The Selective Availability (SA) is a deliberate degradation of the signal when imposed by the U.S. section of the defense. Selective Availability was anticipated to avert martial adversaries from using the perfect GPS signals.

In conclusion, The Global Positioning System (GPS) is a satellite-based steering system that comprises a set-up of 24 satellites placed into the path by the U.S. Defense forces. GPS satellites go round the earth twice a day in a fixed orbit and broadcast signal information to earth. GPS receivers obtain this information then utilize triangulation to gauge the user's exact location. The current GPS receivers are exceptionally perfect, appreciation to their similar multi-channel make. However, the US has a restriction on civilian use. All GPS receivers with the capability of functioning over 18 kilometers altitude as well as 515 meters for every second are classified as munitions (weapons) for which governmental export licenses are compulsory.