Difference between revisions of "Geographical Information System"

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{{Definition|title=Geographical Information system (GIS)
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#Redirect[[Geographical Information System (GIS)]]
|definition=Geographical Information System (GIS) is a tool for analysis and presentation of spatial data. It is a collection of computer hardware, software and geographic data for capturing, managing, analysing and displaying all forms of geographically referenced information.
 
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==What is GIS?==
 
[[Image:GISdefinition.jpg|thumb]]
 
A Geographic Information System organizes large volumes of raw data into a map form for easy comprehension. It divides raw data into layers so it can give you a better understanding for the whole world.
 
 
 
 
 
A GIS is designed for the collection, storage, and analysis of objects and phenomena where geographic location is an important characteristic or critical to the analysis - this definition is broad and applies to a wide variety of methods for storing, accessing, and manipulating geographic information; it does not limit GIS to the computer environment<ref name="Cox">Cox, A., Gifford, F. An overview to geographic information systems. The Journal of Academic Librarianship, Volume 23, Issue 6, November 1997, Pages 449-461</ref> .
 
 
 
 
 
===Why is GIS unique?===
 
GIS handles SPATIAL information - i.e. information referenced by its location in space
 
[[Image:Spatialinfo.jpg|400px|center]]
 
 
 
==GIS Data==
 
GIS stores ''geographic coordinate data'' (spatial data) and ''attribute data''. ''Spatial data'' represents features having known locations on earth. Can be one of points (0-Dimensions), lines (1-Dimensions) or areas (2-Dimensions), while ''attribute data'' is non-graphic information linked to the geographical features (spatial data) describing features eg type of road, name, history.
 
 
 
 
 
===Data formats===
 
Two basic formats for storing and processing coordinate data: Vector and Raster
 
 
 
'''Vector:'''
 
*uses point locations (X,Y coordinate)
 
*''advantage'': less storage space
 
*disadvantage: may be more difficult to perform certain overlay functions
 
 
 
'''Raster:'''
 
*data stored as a matrix of pixels, representing points.
 
*to analyse or overlay multiple data layers, the layers must share a common projection and coordinate system, and layers must have topology established
 
*''advantage'': can perform neighbourhood analysis easily
 
*''disadvantage'': it is necessary to store the entire matrix
 
 
 
===Data types===
 
[[Image:Mike21data.jpg|thumb|right|Dfs1 Data MIKE 21]]
 
*DFS2 Data MIKE 21
 
*Dfs1 Data MIKE 21
 
*XYZ Data
 
*Wave time series & Rose
 
*Scanned Maps
 
*CAD drawing
 
[[Image:CADdrawing.jpg|thumb|right|CAD drawing]]
 
'''Additional Data'''
 
*Land use
 
*Sediment classification
 
*Satellite images
 
*Geographical maps
 
*Reports (design, licenses, Site investigation), etc.
 
 
 
 
 
 
 
 
 
 
 
Map data is separated and stored in layers usually based on common geographical themes or data type. And alternative is objected-oriented GIS, where geographical and all other information regarding a feature stored as an object.
 
 
 
==GIS functions==
 
*Data input
 
*Storage
 
*Management
 
*Analysis
 
*Output
 
 
 
 
 
===Data input===
 
Data input can by via:
 
*keyboard entry
 
*digitising maps
 
*digital scanning (like a photocopy)
 
 
 
===Storing data using Geodatabase===
 
[[Image:Geodatabase.jpg|400px|right]]
 
Geodatabase is a container for spatial and non- spatial data that can be organized in a certain structure. It has the advantages of providing a single, consolidated data storage for field measurements and all types of data used, and the ability of controlling data entry by applying validation rule on the attributes.
 
<br style="clear:both;"/>
 
 
 
===Data management===
 
Database management system controls the way data are stored and retrieved. This includes verifying geographic coordinates and examining for accuracy.
 
 
 
===GIS analysis===
 
GIS analysis creates new data by manipulating existing data or analyzing relationships between sets of data. It's basic operations include:
 
*retrieval
 
*map generalization
 
*map abstractions
 
*map sheet manipulation
 
*map abstractions
 
*map sheet manipulation
 
*buffer generation
 
*polgygon overlay and dissolve
 
*measurements
 
*digital terrain analysis, and
 
*network analysis<ref name="Cox"/>
 
 
 
===Output===
 
The display of output is achieved through printers and computer screens.
 
 
 
==Benefits of GIS==
 
GIS has many benefits, which include:
 
*ability to integrate different databases into one environment
 
*ability to display and manage spatial data in a spatial contect
 
*rapid production of specialized map and graphic products
 
*performs complex spatial analysis
 
 
 
==Coastal Zone Management and GIS==
 
[[Image:GISCZM3.jpg|350px|left|Coastal Zone management: GIS perspective]]
 
GIS stores all data relevant for [[Coastal Zone Management]]. It handles data on all spatial scales (North Egypt coast vs. a single harbour) and is a powerful analysis tool, allowing the comparison of measurements from different years, as well as overlay analysis of measurements and modelling results.
 
<br style="clear:both;"/>
 
:<small>Fig: Coastal Zone Management: GIS perspective</small>
 
 
 
==External links==
 
*[http://www.gisig.it/ GISIG] –- - Geographical Information Systems International Group
 
*[http://www.geo.ed.ac.uk/home/giswww.html GIS WWWW resource list] of servers likely to be of interest to the GIS community
 
*[http://support.esri.com/index.cfm?fa=knowledgebase.gisDictionary.gateway GIS dictionary]
 
*[http://en.wikipedia.org/wiki/Geographic_information_system Wikipedia: GIS]
 
 
 
==References==
 
<references/>
 
 
 
 
 
 
 
''8th January, Ulrik Lumborg, DHI.''
 
 
 
(Caitlin 09:53, 18 January 2007 (Romance Standard Time))
 

Latest revision as of 15:54, 5 October 2021