The global positioning system Essay

Write a brief sum-up of the followers ( no more than half a page typewritten on each point – usage the cyberspace as research tool – mention your beginnings

1 ) Global positioning system

The Global Positioning System ( GPS ) is a space-based radio-navigation system that provides dependable placement, pilotage, and timing services. There are 3 constituents to the GPS system: 1 ) satellites revolving the Earth, 2 ) control & A ; supervising Stationss on Earth and 3 ) the GPS receiving systems owned by users. The orbiters act as mention points to cipher places accurate to a affair of metres by airing wireless signals from infinite. A GPS receiving system on Earth so measures the clip it takes the wireless signals to go from four or more orbiters to its location, calculates the distance to each orbiter, and from this computation determines the user ‘s longitude, latitude, and altitude plus speed and clip, 24 hours a twenty-four hours in all conditions, anyplace in the universe. The procedure by which this is achieved is known as triangulation.

The GPS system was developed & amp ; implemented by the U.S. military with the primary intent of heightening the pilotage effectivity of U.S. and allied military. It was subsequently extended to civilian users, supplying GPS services to civilian users on a uninterrupted world-wide footing freely. Therefore, for anyone with a GPS receiving system, the system will supply location and clip information. Now, GPS pilotage has become a pillar of air power, land & A ; nautical transit systems worldwide. It is used in catastrophe alleviation & A ; exigency services, banking, nomadic phone operations, the control of power grids, agribusiness, land surveying, function, excavation and even in recreational activities such as golf & A ; seafaring.

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In the U.S. Air Force maintained ( commanding the infinite & A ; control sections ) GPS system called NAVSTAR, 24 chief orbiters in 6 orbits circle the Earth every 12 hours. Presently other nations/bodies that maintain or are be aftering a GPS system are: Soviet union with a configuration called GLONASS ; the European Union with programs to establish 30 orbiters to organize a system named Galileo ; and China ‘s Beidou Navigation System.

2 ) Selective Handiness

Selective handiness ( S/A ) is a characteristic of the GPS system that, until terminated in 2000 by a presidential order, deliberately degraded the civilian signal ‘s truth. In the NAVSTAR system, pilotage signals are broadcast by each orbiter on two frequences: 1575.42 MHz for the military and 1227.6 MHz for civilian usage. These bearer moving ridges are modulated by two pseudo-random binary pulsation trains: a 1-megabit/second civilian C/A-code ( harsh acquisition codification ) and a 10-megabit/second military P-code ( preciseness codification ) . With selective handiness, mistakes of up to 328ft were added to the publically available pilotage signals, with the purpose of forestalling enemy usage of civilian GPS receiving systems for preciseness arm counsel because missiles & A ; heavy weapon missiles use GPS signals to find their places and speeds.

However, due to safety concerns related to the increasing usage of GPS by civilian Marine vass and aircrafts, selective handiness was terminated. Soon, un-augmented civilian GPS gives an mistake discrepancy, for horizontal distances, of 100 foot with a chance of 95 % i.e. 95 % of the clip the reported location is within 100ft of the true location. The typical horizontal truth is about 30 foots compared with 330 foots with selective handiness ; while perpendicular truth or height, is about half as precise. The Doppler Effect ( the alteration in frequence of a moving ridge for an perceiver traveling comparative to the beginning of the moving ridge ) allows receiving systems to find a user ‘s speed to an truth of about 3 pess per second. The unaugmented military signal, meanwhile, has a horizontal mistake discrepancy of less than 10 foot.

Mentions for Numberss 1 & A ; 2 & A ; 5:

  • Global Positioning System. 14 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;
  • GPS General Information. 14 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;
  • GPS Tutorial. Trimble Worldwide. 14 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;
  • GPS. Encyclop?dia Britannica. 14Nov 2009. & lt ; hypertext transfer protocol: // & gt ; .

3 ) GRS80 and the Geodetic Reference System

GRS80 ( Geodetic Reference System 1980 ) is a planetary geocentric system based on the ellipsoid adopted by the International Union of Geodesy and Geophysics ( IUGG ) in 1979. A geodesic mention system is a data point, which specifies the size and form of the Earth, and a basal point from which the latitude and longitude of all other points are referenced. GRS80 has a 6,378.137 kilometer semi-major axis and a 1:298.257 flattening. The GRS80 is the mention ellipsoid that most closely approximates the true size and form of the Earth.

The system serves as an official mention for geodesic, geophysical, astronomical and hydrographic applications ; and is the footing for geodesic placement by the Global Positioning System ( GPS ) .

4 ) WGS84

The WGS84 ( World Geodetic System 1984 ) is comprised of a standard co-ordinate frame for the Earth, a mention ellipsoid for natural height informations and a gravitative equipotential surface ( the geoid ) that defines the nominal sea degree. GRS80 is the mention ellipsoid for the WGS84 co-ordinate system.

The WGS84 is a alteration of old World Geodetic System criterions ( WGS 72, WGS 66, and WGS 60 ) and is valid up to about 2010. The U.S. military uses the WGS84 as a footing for the GPS system. Therefore, coordinates soon provided by GPS receiving systems are based on the WGS84 although GPS package exists to interpret the co-ordinates to other data point. Different data point usage different estimations for the precise form and size of the Earth i.e. mention ellipsoids. There are different data point in being because anterior to GPS handiness, national map doing organisations did non hold a common surveying mention point and merely produced maps for their vicinity.

Mentions for Numberss 3 & A ; 4:

  • Geodetic Reference System 1980. H. Moritz. & lt ; hypertext transfer protocol: // & gt ;
  • GPS for Land Surveyors. Sickle, Jan Van. 2001 2nd Ed. , CRC Press.
  • Geodetic system. Wikipedia, The Free Encyclopedia. 14 Nov 2009 & lt ; hypertext transfer protocol: // title=Geodetic_system & A ; oldid=325304946 & gt ;

5 ) DGPS

Assorted augmentation methods exist for bettering the truth of both military and civilian GPS systems. Therefore, when positional information is required with preciseness, users can take advantage of differential GPS ( DGPS ) techniques. DGPS corrects for several of import beginnings of GPS mistakes, peculiarly ionospheric hold ; it was besides used to rectify for selective handiness before it was turned off.

Since mistakes will impact every GPS receiving system in a given country about every bit, differential pilotage works with a stationary base station that sits at an accurately known place on the land and continuously proctors the signals being broadcast by GPS orbiters in its position. It so computes and broadcasts real-time pilotage corrections to nearby GPS receiving systems. In kernel, each local receiving system subtracts its place solution from the base station ‘s solution, therefore extinguishing any statistical mistakes common to the two. The truth of the corrections depends on the distance between the user and the DGPS receiving system. As the distance additions, the mistakes at the two sites will non correlate, ensuing in less precise differential corrections. DGPS services are widely available from both commercial and authorities beginnings.

The U.S. Coast Guard maintains a web of base Stationss, conveying corrections over wireless beacons covering most of the U.S. A alteration of DGPS is preciseness farming where differential corrections are encoded within the normal broadcasts of commercial wireless Stationss and husbandmans having these broadcasts use them to direct their field equipment with greater truth.


  • GPS. Encyclop?dia Britannica. 14Nov 2009 & lt ; hypertext transfer protocol: // & gt ;

6 ) Digitizer

This is a hardware constituent of the Geographic Information System ( GIS ) . A digitiser is a device used to capture two-dimensional co-ordinate informations, normally as ten and Y co-ordinates, from bing parallel maps for digital usage within a computerized plan such as a GIS. A digitiser produces vector informations as an operator traces points, lines, and polygon boundaries from a map, utilizing crosshairs.

A digitiser normally comes in the form of a artworks pulling tablet consisting of a all right grid of thin wires encased in a dense stable substance such as fibreglass. The wires sense the x-y places of a pointer that is moved over the digitiser surface. More precise information is generated by the digitiser depending on how finely & A ; accurately the wires are spaced. A map or aerial exposure is placed over the digitiser and after set uping a co-ordinate system, an analyst traces the lineation of countries and Markss places of points and lines. As the pointer moves, its consecutive places are digitally recorded by the digitiser as a sequence of co-ordinate braces.


  • Glossary. GIS & A ; Remote Sensing Lab, UNBC. 14 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;
  • Surveying, Volume II. S K Duggal. New Delhi: Tata McGraw-Hill, 2004.

7 ) FGDC

The Federal Geographic Data Committee ( FGDC ) is an interagency commission that promotes the co-ordinated development, usage, sharing, and airing of geospatial informations on a national footing. This countrywide informations publication attempt is known as the National Spatial Data Infrastructure ( NSDI ) , and is a physical, organisational, and practical web designed to enable the development and sharing of U.S. digital geographic information resources. FGDC activities are administered through the FGDC Secretariat, hosted by the U.S. Geological Survey.

The FGDC is a 19 member interagency commission composed of representatives from the Executive Office of the President, and Cabinet degree and independent Federal bureaus. The Secretary of the Department of the Interior chairs the FGDC, with the Deputy Director for Management, Office of Management and Budget ( OMB ) as Vice-Chair. Numerous stakeholder organisations participate in FGDC activities stand foring the involvements of province and local authorities, industry, and professional organisations.

The FGDC develops geospatial informations criterions ( that facilitate the development, sharing, and usage of geospatial informations ) for implementing the NSDI, in audience and cooperation with province, local, and tribal authoritiess ; the private sector and academic community ; and to the extent executable, the international community.


  • The Federal Geographic Data Committee. 14 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;

8 ) SDTS

Spatial Data Transfer Standard ( SDTS ) is a standard mechanism for file awaying and reassigning of spacial informations ( including metadata ) between different computing machine platforms, while continuing information significance and minimising the demand for information external to the transportation. The SDTS specifies exchange concepts, such as format, construction, and content, for spatially referenced vector and raster ( including gridded ) informations. Execution of SDTS is of important involvement to users and manufacturers of digital spacial informations because of the possible for increased entree to and sharing of spacial informations, the decrease of information loss in informations exchange, and the addition in the quality and unity of spacial informations.

The SDTS is a criterion for informations transportation, as opposed to a criterion for informations processing. It does non replace bing Geographic Information System ( GIS ) processing formats and is designed specifically for spacial informations. The SDTS serves as the compulsory spacial informations transportation mechanism for all Federal bureaus and is available for usage by State and local authoritiess, the private sector, and research and academic organisations. The National Mapping Division of the U.S. Geological Survey is the care bureau for the criterion.


  • What is SDTS? U.S. Department of the Interior & A ; U.S. Geological Survey. & lt ; hypertext transfer protocol: // & gt ;
  • USGS Fact Sheet 077-99. U.S. Department of the Interior & A ; U.S. Geological Survey. & lt ; hypertext transfer protocol: // & gt ;

9 ) Linda Williams Pickle

Linda Williams Pickle is an author/researcher whose work focuses on developing better statistical methods and informations visual image tools for analysing and showing wellness related informations. Ms. Pickle is senior mathematical statistician and coordinator of geographic research in the statistical research and applications subdivision of the National Cancer Institute ‘s ( NCI ) Division of Cancer Control and Population Sciences, Surveillance Research Program.

Her research has led to improved techniques for patterning incidence rates at the county degree, while taking into history hierarchies and spacial relationships. Without taking into history these hierarchies, simple comparings or arrested development analyses yield wrong consequences. This method of taking into history hierarchies is used by the American Cancer Society for their one-year Cancer Facts and Figures publication.

Based on this method, bunch designation and spacial statistical mold have been incorporated into standard GIS analytic patterns. This method is besides used in the NCI ‘s Cancer Atlas, admiting that malignant neoplastic disease rates vary geographically. Topographic point is of import for malignant neoplastic disease & A ; epidemiological surveies because of geographic differences in environmental exposures, cultural attitudes toward hazardous behaviours and preventative wellness attention, local public wellness policies, handiness of services by socioeconomic degree, and the agencies by which occupants obtain wellness information. For illustration, high lung malignant neoplastic disease mortality rates seen in coastal metropoliss were found to be due to asbestos exposure from shipyard work during World War II while high unwritten malignant neoplastic disease rates among white adult females in southeasterly provinces were found to be caused by their wont of dunking snuff ( smokeless baccy ) . GIS can therefore be a utile tool for gauging exposure to environmental contaminations by supplying information about possible exposures that can non be obtained through traditional epidemiologic methods.


  • Commentary on ‘Improving in writing shows by commanding creativeness ‘ . L. W. Pickle. CHANCE, Vol. 21, No. 2. ( 1 June 2008 ) , pp. 53-53.
  • GIS Users Excel in Communication, Service and Vision. & lt ; hypertext transfer protocol: // sid= & A ; nm= & A ; type=MultiPublishing & A ; mod=PublishingTitles & A ; mid=13B2F0D0AFA04476A2ACC02ED28A405F & A ; tier=4 & A ; id=4AD0575D2FB943518CA219D4AF54849C & gt ;
  • Applications of GIS to malignant neoplastic disease research at the National Cancer Institute. Pickle LW, Heineman EF, Ward MH, Nuckols JR, Gumpertz ML, Bell BS. Proceedings of 2001 ESRI international wellness geographies conference ; Washington, DC. 2001.

10 ) ColorBrewer

ColorBrewer is an on-line Flash application designed to assist people choice appropriate informations colourising strategies for maps and other artworks including consecutive ( choropleths ) , diverging ( informations with interruption points ) , and qualitative ( distinct categorical information ) . ColorBrewer is a colour diagnostic tool and non an on-line GIS. Therefore users can non lade informations into ColorBrewer but can merely utilize the online maps to prove a given colour strategy.

ColorBrewer was funded by the NSF Digital Government plan. It was designed as portion of the dgQG research enterprise at the GeoVISTA Center at Penn State University. The newest version of the package has characteristics including export to ArcGIS and showing of colour strategies based on end-use such as appropriate for colour sightlessness, run offing or print. The National Cancer Institute has taken the ColorBrewer colour inclines and incorporated them into ColorTool, a free plugin for ArcMap.


  • Colorbrewer: Color Advice for Maps. & lt ; hypertext transfer protocol: // & gt ;

11 ) Gerardus Mercator and his parts to map projection

Gerardus Mercator was a Flemish map maker ( 1512-1594 ) . He created the Mercator projection universe map, on which analogues and acmes are rendered as consecutive lines spaced so as to bring forth at any point an accurate ratio of latitude to longitude. He besides introduced the term Atlas for a aggregation of maps. He is known as the foremost geographer of the sixteenth century, printing a series of printed cartographic plants: in 1537 a map of Palestine, in 1538 a map of the universe on a dual cordate projection, and about 1540 a map of Flanders. In 1564, he was appointed to tribunal “ cosmographist ” to Duke Wilhelm of Cleve.

His Mercator projection enabled seamans to maneuver a class over long distances by plotting consecutive lines without continual accommodation of compass readings, going the standard map projection for maritime intents. This technique was used in his 1569 map of the universe. In the Mercator projection, the acmes are every bit spaced, parallel perpendicular lines, and the analogues of latitude are parallel, horizontal heterosexual lines, spaced farther and farther apart as their distance from the Equator increases. This projection is widely used for pilotage charts, because any consecutive line on a Mercator-projection map is a line of changeless true bearing that enables a sailing master to plot a straight-line class. However, the projection is less practical for universe maps because the graduated table is distorted ; with countries farther off from the equator looking disproportionately big. E.g. on a Mercator projection, Greenland appears to be greater than the continent of South America which is non so.


  • Mercator, Gerardus. Encyclopedia Britannica. 16 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;

12 ) Claudius ptolemaeus

Claudius Ptolemaeus ( AD 100 – 170 ) was an Egyptian uranologist, mathematician, and geographer of Grecian descent who flourished in Alexandria during the second century AD. He was the greatest figure of the ancient universe in the promotion of geographics and mapmaking. He postulated a geocentric ( Earth-centered ) theoretical account of the existence now known as the Ptolemaic system. His geocentric system ( any theory of the construction of the solar system or the existence in which the Earth is assumed to be at the Centre of all ) was by and large accepted until the sixteenth century, after which it was superseded by heliocentric theoretical accounts such as that of Nicolaus Copernicus. Ptolemy was pre-eminently responsible for the geocentric cosmology that prevailed in the Islamic universe and in mediaeval Europe ; with his proposal of the Ptolemaic system-a incorporate system in which each heavenly organic structure is attached to its ain domain and the set of domains nested so that it extends without spreads from the Earth to the celestial domain.

Ptolemy ‘s monumental work, the Guide to Geography was produced in eight volumes and provided all the information and techniques required to pull maps of the part of the universe known by Ptolemy ‘s coevalss. The first volume discussed basic rules and dealt with map projection and Earth building. The following six volumes carried a list of the names of some 8,000 topographic points and their approximate latitudes and longitudes. The 8th volume contained instructions for fixing maps of the universe and treatments on mathematical geographics and other cardinal rules of mapmaking. Ptolemy besides devised ways of pulling a grid of lines on a level map to stand for the circles of latitude and longitude on the Earth.


  • Ptolemy. Encyclopedia Britannica.16 Nov 2009. & lt ; hypertext transfer protocol: // & gt ; .
  • Map. Encyclopedia Britannica. 16 Nov 2009. & lt ; hypertext transfer protocol: // & gt ; .

13 ) Alexander Ross Clarke

Alexander Ross Clarke was an English geodesist whose computations of the size and form of the Earth were the first to come close recognized modern values with regard to both polar flattening and equatorial radius. His 1866 mention ellipsoid, known as Clarke 1866 became a standard mention for U.S. geodesy, even after the credence of other figures by the International Union of Geodesy and Geophysics in 1924. It is still used today, peculiarly in English-language states and countries. In his 1880 book Geodesy he described a different ellipsoid, known as Clarke 1880, which is used chiefly in Africa.

He was responsible for the chief triangulation ( long-distance trigonometric appraising ) of the British Isles and published the consequences of the first geodesic study of Great Britain in 1861. He was besides entrusted with comparing the criterions of length for mensurating an international discharge of triangulation from Ireland to Russia, printing the consequences of that in 1866 titled The Comparison of Standards of Length.


  • Clarke, Alexander Ross. Encyclopedia Britannica. 16 Nov 2009. & lt ; hypertext transfer protocol: // & gt ;
  • Alexander Ross Clarke. Wikipedia, The Free Encyclopedia. 16 Nov 2009 & lt ; hypertext transfer protocol: // title=Alexander_Ross_Clarke & A ; oldid=310529332 & gt ;


LANDSAT is any of a series of remote-controlled U.S. scientific orbiters and the Landsat plan is the longest running endeavor for acquisition of imagination of Earth from infinite. The first three Landsat orbiters were launched in 1972, 1975, and 1978 and the most recent, Landsat 7, was launched on April 15, 1999. The orbiters were chiefly designed to roll up information about the Earth ‘s natural resources, including the location of mineral sedimentations and the status of woods and farming parts and besides to supervise atmospheric and pelagic conditions and to observe fluctuations in pollution degree and other ecological alterations.

Landsat 5 and 7 are approaching the terminal of their operational life-times ; therefore a new orbiter, the Landsat Data Continuity Mission, is planned for launch in December 2012. Images from the Landsat plan are archived in the United States and at Landsat having Stationss around the universe and are a alone resource for research on planetary climatic alteration, environmental alteration surveies and are used as applications in agribusiness, geology, forestry, regional planning, instruction and national security.


  • Landsat. Encyclopedia Britannica. 16 Nov 2009. & lt ; hypertext transfer protocol: // & gt ; .
  • Landsat plan. Wikipedia, The Free Encyclopedia. 17 Nov 2009 & lt ; hypertext transfer protocol: // title=Landsat_program & A ; oldid=320972130 & gt ; .

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