introduction of gis

8/10/2019 Introduction of GIS

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INTRODUCTIONOF

GEOGRAPHIC INFORMATIONSYSTEM


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All of these applications consider the location of certain features onthe landscape in relation to other features. For instance, in

assessment, the location of soil types relative to property parcels isconsidered, whereas in planning and zoning, the location of animalconfinement facilities relative to residential areas might be relevant.

A geographic information system (GIS) allows the user to examineand visualize these relationships.


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DEFINITION OF GIS

A geographic information system (GIS) is a computer -based tallows you to create, manipulate, analyse, store and displayinformation based on its location. GIS makes it possible to integratedifferent kinds of geographic information, such as digital maps, aerialphotographs, satellite images and global positioning system data(GPS), along with associated tabular database information (e.g.,attributes' or characteristics about geographic features).


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Using GIS, we can incorporate all of this information into a singlesystem and execute common database operations. For example, GIS

allows you to perform statistical analysis or spatial queries, to explorewhat-if' scenarios, and to create predictive models.

GIS allows you to examine and analyse geographic information atdifferent levels of detail or from different perspectives. Then, it enablesyou to customize the display of your maps and analyses forpresentation to particular audiences.


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GIS accuracy depends upon source data, and how it is encoded to be data referenced.Land surveyors have been able to provide a high level of positional accuracy utilizingthe GPS-derived positions. High-resolution digital terrain and aerial imagery,computers and Web technology are changing the quality, utility, and expectations of GIS

to serve society on a grand scale, but nevertheless there are other source data thathave an impact on overall GIS accuracy like paper maps, though these may be oflimited use in achieving the desired accuracy since the aging of maps affects theirdimensional stability.

In developing a digital topographic database for a GIS, topographical maps are the mainsource, and aerial photography and satellite imagery are extra sources for collecting

data and identifying attributes which can be mapped in layers over a location facsimileof scale. The scale of a map and geographical rendering area representation type arevery important aspects since the information content depends mainly on the scale setand resulting locatability of the map's representations. In order to digitize a map, themap has to be checked within theoretical dimensions, then scanned into a raster formatand resulting raster data has to be given a theoretical dimension by a rubbersheeting/warping technology process.


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DATA REPRESENTATION

GIS data represents real objects (such as roads, land use, elevation, trees,waterways, etc.) with digital data determining the mix. Real objects can bedivided into two abstractions: discrete objects (e.g., a house) and continuousfields (such as rainfall amount, or elevations). Traditionally, there are twobroad methods used to store data in a GIS for both kinds of abstractionsmapping references: raster images and vector. Points, lines, and polygons

are the stuff of mapped location attribute references. A new hybrid method ofstoring data is that of identifying point clouds, which combine three-dimensional points with RGB information at each point, returning a "3D colorimage". GIS thematic maps then are becoming more and more realisticallyvisually descriptive of what they set out to show or determine.


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DATA CAPTURE

Data capture entering information into the system consumes mof the time of GIS practitioners. There are a variety of methods usedto enter data into a GIS where it is stored in a digital format.

Existing data printed on paper or PET film maps can be digitizscanned to produce digital data. A digitizer produces vector daoperator traces points, lines, and polygon boundaries from a map.Scanning a map results in raster data that could be further processedto produce vector data.
http://en.wikipedia.org/wiki/PET_film_(biaxially_oriented)http://en.wikipedia.org/wiki/Digitizerhttp://en.wikipedia.org/wiki/Vector_graphicshttp://en.wikipedia.org/wiki/Image_scannerhttp://en.wikipedia.org/wiki/Image_scannerhttp://en.wikipedia.org/wiki/Vector_graphicshttp://en.wikipedia.org/wiki/Digitizerhttp://en.wikipedia.org/wiki/PET_film_(biaxially_oriented)


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Remotely sensed data also plays an importantrole in data collection and consist of sensorsattached to a platform. Sensors includecameras, digital scanners and lidar , whileplatforms usually consist of aircraft andsatellites . Recently with the development ofminiature UAVs , aerial data collection isbecoming possible at much lower costs, and ona more frequent basis.

The majority of digital data currently comes fromphoto interpretation of aerial photographs. Soft-copy workstations are used to digitize featuresdirectly from stereo pairs of digital photographs.These systems allow data to be captured in twoand three dimensions, with elevations measureddirectly from a stereo pair using principles ofphotogrammetry .
http://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Lidarhttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Miniature_UAVhttp://en.wikipedia.org/wiki/Photo_interpretationhttp://en.wikipedia.org/wiki/Stereoscopyhttp://en.wikipedia.org/wiki/Photogrammetryhttp://en.wikipedia.org/wiki/Photogrammetryhttp://en.wikipedia.org/wiki/Stereoscopyhttp://en.wikipedia.org/wiki/Photo_interpretationhttp://en.wikipedia.org/wiki/Miniature_UAVhttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Lidarhttp://en.wikipedia.org/wiki/Remote_sensing


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Satellite remote sensing provides another important source of spatial data. Heresatellites use different sensor packages to passively measure the reflectance fromparts of the electromagnetic spectrum or radio waves that were sent out from anactive sensor such as radar. Remote sensing collects raster data that can be furtherprocessed using different bands to identify objects and classes of interest, such asland cover.

When data is captured, the user should consider if the data should be captured witheither a relative accuracy or absolute accuracy, since this could not only influencehow information will be interpreted but also the cost of data capture.

After entering data into a GIS, the data usually requires editing, to remove errors, or

further processing. For vector data it must be made "topologically correct" before itcan be used for some advanced analysis. For example, in a road network, linesmust connect with nodes at an intersection. Errors such as undershoots andovershoots must also be removed. For scanned maps, blemishes on the sourcemap may need to be removed from the resulting raster . For example, a fleck omight connect two lines that should not be connected.
http://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Raster_graphicshttp://en.wikipedia.org/wiki/Raster_graphicshttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Remote_sensing


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PROJECTIONS, COORDINATE SYSTEMS, ANDREGISTRATION

The earth can be represented by various models, each of which mayprovide a different set of coordinates (e.g., latitude, longitude,elevation) for any given point on the Earth's surface. The simplestmodel is to assume the earth is a perfect sphere. As moremeasurements of the earth have accumulated, the models of the earthhave become more sophisticated and more accurate. In fact, there aremodels called datums that apply to different areas of the earth toprovide increased accuracy, like NAD83 for U.S. measurements, athe World Geodetic System for worldwide measurements.
http://en.wikipedia.org/wiki/Datum_(geodesy)http://en.wikipedia.org/wiki/NAD83http://en.wikipedia.org/wiki/World_Geodetic_Systemhttp://en.wikipedia.org/wiki/World_Geodetic_Systemhttp://en.wikipedia.org/wiki/NAD83http://en.wikipedia.org/wiki/Datum_(geodesy)


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APPLICATIONS The implementation of a GIS is often driven by jurisdictional (such as a city),

purpose, or application requirements. Generally, a GIS implementation maybe custom-designed for an organization. Hence, a GIS deploymentdeveloped for an application, jurisdiction, enterprise, or purpose may not benecessarily interoperable or compatible with a GIS that has been developefor some other application, jurisdiction, enterprise, or purpose.

GIS provides, for every kind of location based organization, a platform toupdate geographical data without wasting time to visit the field and update adatabase manually. GIS when integrated with other powerful enterprisesolutions like SAP helps creating powerful decision support systementerprise level.
http://en.wikipedia.org/wiki/Interoperabilityhttp://en.wikipedia.org/wiki/Decision_support_systemhttp://en.wikipedia.org/wiki/Decision_support_systemhttp://en.wikipedia.org/wiki/Interoperability


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Many disciplines can benefit from GIS technology. An activeGIS market has resulted in lower costs and continual improvements inthe hardware and software components of GIS, and usage in thefields of science, government, business , and industry , withapplications including real estate , public health , crime mappingnational defense , sustainable development , natural resourcesclimatology , landscape architecture , archaeology , regional andcommunity planning, transportation and logistics. GIS is also diverging

into location-based services , which allows GPS-enabled mobiledevices to display their location in relation to fixed objects (nearestrestaurant, gas station, fire hydrant) or mobile objects (friends,children, police car), or to relay their position back to a central serverfor display or other processing.
http://en.wikipedia.org/wiki/Businesshttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Real_estatehttp://en.wikipedia.org/wiki/Public_healthhttp://en.wikipedia.org/wiki/Crime_mappinghttp://en.wikipedia.org/wiki/Defense_(military)http://en.wikipedia.org/wiki/Sustainable_developmenthttp://en.wikipedia.org/wiki/Natural_resourceshttp://en.wikipedia.org/wiki/Climatologyhttp://en.wikipedia.org/wiki/Landscape_architecturehttp://en.wikipedia.org/wiki/Archaeologyhttp://en.wikipedia.org/wiki/Location-based_servicehttp://en.wikipedia.org/wiki/Location-based_servicehttp://en.wikipedia.org/wiki/Location-based_servicehttp://en.wikipedia.org/wiki/Location-based_servicehttp://en.wikipedia.org/wiki/Archaeologyhttp://en.wikipedia.org/wiki/Landscape_architecturehttp://en.wikipedia.org/wiki/Landscape_architecturehttp://en.wikipedia.org/wiki/Climatologyhttp://en.wikipedia.org/wiki/Natural_resourceshttp://en.wikipedia.org/wiki/Sustainable_developmenthttp://en.wikipedia.org/wiki/Defense_(military)http://en.wikipedia.org/wiki/Defense_(military)http://en.wikipedia.org/wiki/Crime_mappinghttp://en.wikipedia.org/wiki/Public_healthhttp://en.wikipedia.org/wiki/Real_estatehttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Business


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introduction of gis

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