Difference between revisions of "Geographical Information System"

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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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#Redirect[[Geographical Information System (GIS)]]
 
 
==What is GIS?==
 
[[Image:GISdefinition.jpg|thumb]]
 
;Simple definition : A Geographic Information System organizes large volumes of raw data into a map form for easy comprehension.
 
:GIS 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>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
 
**Information referenced by its location in space
 
[[Image:Spatialinfo.jpg|400px|centre]]
 
 
 
 
 
==GIS Data==
 
GIS stores ''geographic coordinate data'' (spatial data) and ''attribute data''.
 
 
 
'''Spatial data:'''
 
*represent features having known locations on earth
 
*one of: points (0D), lines (1D) or areas (2D)
 
 
 
'''Attribute data:'''
 
*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
 
*Disadvantage: it is necessary to store the entire matrix
 
*Advantage: can perform neighbourhood analysis easily
 
 
 
 
 
 
 
===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===
 
*keyboard entry, digitize maps; digital scanning (like a photocopy)
 
 
 
===Storing data using Geodatabase===
 
*Geodatabase is a container for spatial and non- spatial data that can be organized in a certain structure.
 
*Advantages:
 
**provide a single, consolidated data storage for field measurements and all types of data used.
 
**Controlling data entry by applying validation rule on the attributes.
 
 
 
[[Image:Geodatabase.jpg|400px|centre]]
 
 
 
 
 
===Data management===
 
*database management system controls the way data are stored and retrieved
 
*includes verifying geographic coordinates and examining for accuracy
 
 
 
===GIS analysis===
 
*create new data by manipulating existing data or analyzing relationships between sets of data
 
*basic operations: retriecal, 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 (Cox and wotshisface, 1997).
 
 
 
===Output===
 
*display of output through printers and computer screens
 
 
 
==Benefits of GIS==
 
*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
 
 
 
==CZM and GIS==
 
 
 
*GIS stores all data relevant for the [[CZM]]
 
*GIS handles data on all spatial scales (North Egypt coast vs. a single harbour)
 
*GIS is a powerful analysis tool.
 
**Comparison of measurements from different years
 
**Overlay analysis of measurements and modelling results
 
 
 
 
 
 
 
[[Image:GISCZM3.jpg|500px|centre|Coastal Zone management: GIS perspective]]
 
 
 
==External links==
 
[http://en.wikipedia.org/wiki/Geographic_information_system Wikipedia: GIS]
 
 
 
[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]
 
 
 
 
 
==References==
 
<references/>
 
 
 
 
 
 
 
''8th January, Ulrik Lumborg, DHI.''
 

Latest revision as of 15:54, 5 October 2021