gis geographical information system presented by: madam

8/14/2019 GIS Geographical Information System Presented by: Madam

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GISGIS

Geographical Information SystemGeographical Information System

Presented By: Madam Rabi(Geologist)Presented By: Madam Rabi(Geologist)


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GISGIS

Geographical Information System,system of capturing,Geographical Information System,system of capturing,storing,analyzng,managing,representing the linked layersstoring,analyzng,managing,representing the linked layersland related data on the surface of earthland related data on the surface of earth


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ARC GISARC GIS

GIS as one of the most powerful of all informationGIS as one of the most powerful of all informationtechnologies because it focuses on integratingtechnologies because it focuses on integratingknowledge from multiple sources and creates aknowledge from multiple sources and creates a

crosscutting environment for collaboration.crosscutting environment for collaboration.

GIS is attractive to most people who encounter itGIS is attractive to most people who encounter itbecause it is both intuitive and cognitive. It combinesbecause it is both intuitive and cognitive. It combinesa powerful visualization environment with a stronga powerful visualization environment with a strong

analytic and modeling framework that is rooted in theanalytic and modeling framework that is rooted in thescience of geography.science of geography.


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Three views of GISThree views of GIS

The geodatabase view. The geodatabase view. The map view The map view The geoprocessing view The geoprocessing viewThese three GIS views areThese three GIS views arerepresented in Arc gis by therepresented in Arc gis by the

catalog and the geodatabasecatalog and the geodatabase(a GIS is a collection of (a GIS is a collection of geographic datasets), thegeographic datasets), themap (a GIS is an intelligent map (a GIS is an intelligent map view), and the toolbox map view), and the toolbox (a GIS is a set of (a GIS is a set of geoprocessing tools).geoprocessing tools).

Together, all three areTogether, all three arecritical parts of a completecritical parts of a completeGIS and are used at varyingGIS and are used at varyinglevels in all GIS applications.levels in all GIS applications.


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The Geodatabase viewThe Geodatabase view

.. A GIS manages geographic information. One wayA GIS manages geographic information. One wayto think of a GIS is as a spatial database containingto think of a GIS is as a spatial database containingdatasets that represent geographic information indatasets that represent geographic information interms of a generic GIS data model features,terms of a generic GIS data model features,rasters, attributes, topologies, networks, and sorasters, attributes, topologies, networks, and soforth.forth.

GIS datasets are like map layers; they areGIS datasets are like map layers; they aregeographically referenced so that they overlaygeographically referenced so that they overlayonto the earth's surface. In many cases, theonto the earth's surface. In many cases, thefeatures (points, lines, and polygons) share spatialfeatures (points, lines, and polygons) share spatialrelationships with one another. For example,relationships with one another. For example,adjacent features share a common boundary.adjacent features share a common boundary.Many linear features connect at their endpoints.Many linear features connect at their endpoints.Many point locations fall along linear featuresMany point locations fall along linear features(e.g., address locations along roads).(e.g., address locations along roads).


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The map viewThe map view

A GIS is a set of intelligent maps and other views thatA GIS is a set of intelligent maps and other views thatshow features and feature relationships on the earth'sshow features and feature relationships on the earth'ssurface. Various map views of the underlyingsurface. Various map views of the underlyinggeographic information can be constructed and usedgeographic information can be constructed and usedas windows into the geographic database to supportas windows into the geographic database to supportquery, analysis, and editing of geographic information.query, analysis, and editing of geographic information.Each GIS has a series of two-dimensional (2D) andEach GIS has a series of two-dimensional (2D) andthree-dimensional (3D) map applications that providethree-dimensional (3D) map applications that providerich tools for working with geographic informationrich tools for working with geographic informationthrough these views.through these views.


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Geoprocessing viewGeoprocessing view

A GIS is a set of information transformation tools thatA GIS is a set of information transformation tools thatderive new information from existing datasets. Thesederive new information from existing datasets. Thesegeoprocessing functions take information fromgeoprocessing functions take information fromexisting datasets, apply analytic functions, and writeexisting datasets, apply analytic functions, and write

results into new derived datasets. Geoprocessingresults into new derived datasets. Geoprocessinginvolves the ability to string together a series of involves the ability to string together a series of operations so that users can perform spatial analysisoperations so that users can perform spatial analysisand automate data processingall by assembling anand automate data processingall by assembling anordered sequence of operations.ordered sequence of operations.

There are numerous spatial operators that can be There are numerous spatial operators that can beapplied to GIS data. The ability to derive newapplied to GIS data. The ability to derive newinformation within a GIS analysis process is one of theinformation within a GIS analysis process is one of thefundamental capabilities in GIS.fundamental capabilities in GIS.


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MapMap

How maps convey geographic informationHow maps convey geographic information

Fundamental GIS concepts are closely linked to maps and theirFundamental GIS concepts are closely linked to maps and their

contents.contents.MapsMaps A map is a collection of map elements laid out andA map is a collection of map elements laid out andorganized on a page. Common map elements include the maporganized on a page. Common map elements include the mapframe with map layers, a scale bar, north arrow, title,frame with map layers, a scale bar, north arrow, title,descriptive text, and a symbol legend.descriptive text, and a symbol legend.

The primary map element is the map frame, and it provides The primary map element is the map frame, and it providesthe principal display of geographic information. Within the mapthe principal display of geographic information. Within the map

frame, geographic entities are presented as a series of mapframe, geographic entities are presented as a series of maplayers that cover a given map extentfor example, map layerslayers that cover a given map extentfor example, map layerssuch as roads, rivers, placenames, buildings, politicalsuch as roads, rivers, placenames, buildings, politicalboundaries, surface elevation, and satellite imagery.boundaries, surface elevation, and satellite imagery.


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Map frameMap frameA map frame contains a series of mapA map frame contains a series of maplayers for a given extent.layers for a given extent.Map layers are thematicMap layers are thematicrepresentations of geographicrepresentations of geographicinformation such as transportation,information such as transportation,water, and elevation. Map layers helpwater, and elevation. Map layers helpconvey information throughconvey information throughDiscrete features such as collections of Discrete features such as collections of points, lines, and polygonspoints, lines, and polygonsMap symbols, colors, and labels thatMap symbols, colors, and labels thathelp describe the objects in the maphelp describe the objects in the mapAerial photography or satellite imageryAerial photography or satellite imagerythat covers the map extentthat covers the map extentContinuous surfaces such as elevationContinuous surfaces such as elevationthat can be represented in a number of that can be represented in a number of waysfor example, as a collection of waysfor example, as a collection of contour lines and elevation points or ascontour lines and elevation points or asshaded relief shaded relief


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Map Layout and compositionMap Layout and compositionAlong with the map frame, a map presents an integrated seriesAlong with the map frame, a map presents an integrated seriesof map elements laid out and arranged on a page. Common mapof map elements laid out and arranged on a page. Common mapelements include a north arrow, a scale bar, a symbol legend,elements include a north arrow, a scale bar, a symbol legend,and other graphical elements. These elements aid in mapand other graphical elements. These elements aid in mapreading and interpretation.reading and interpretation.Map Layout:Map Layout:


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Spatial relationships in a mapSpatial relationships in a map Within a map, such relationships are not explicitlyWithin a map, such relationships are not explicitlyrepresented. Instead, as the map reader, you interpretrepresented. Instead, as the map reader, you interpretrelationships and derive information from the relativerelationships and derive information from the relativeposition and shape of the map elements, such as theposition and shape of the map elements, such as the

streets, contours, buildings, lakes, railways, and otherstreets, contours, buildings, lakes, railways, and otherfeatures. In a GIS, such relationships can be modeledfeatures. In a GIS, such relationships can be modeledby applying rich data types and behaviors (forby applying rich data types and behaviors (forexample, topologies and networks) and by applying aexample, topologies and networks) and by applying acomprehensive set of spatial operators to thecomprehensive set of spatial operators to thegeographic objects (such as buffer and polygongeographic objects (such as buffer and polygonoverlay).overlay).


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Maps help convey geographic relationships that can be interpreted and analyzed byMaps help convey geographic relationships that can be interpreted and analyzed bymap readers. Relationships that are based on location are referred to as spatialmap readers. Relationships that are based on location are referred to as spatialrelationships. Here are some examples.relationships. Here are some examples.Which geographic featuresWhich geographic features connect connect to others (for example, Water Street connectsto others (for example, Water Street connectswith 18th Ave.)?with 18th Ave.)?Which geographic features areWhich geographic features are adjacent adjacent (contiguous) to others (for example, The(contiguous) to others (for example, The

city park is adjacent to the university.)?city park is adjacent to the university.)?Which geographic features areWhich geographic features are contained withincontained within an area (for example, The buildingan area (for example, The buildingfootprints are contained within the parcel boundary.)?footprints are contained within the parcel boundary.)?Which geographic featuresWhich geographic features overlapoverlap (for example, The railway crosses the freeway.)?(for example, The railway crosses the freeway.)?Which geographic features areWhich geographic features are near near others (proximity) (for example, The Courthouseothers (proximity) (for example, The Courthouseis near the State Capitol.)?is near the State Capitol.)?

The feature geometry The feature geometry is equal tois equal to another feature (for example, The city park isanother feature (for example, The city park isequal to the historic site polygon.).equal to the historic site polygon.).

What is the difference in elevation of geographic features (for example, The StateWhat is the difference in elevation of geographic features (for example, The StateCapitol is uphill from the water.)?Capitol is uphill from the water.)?Which feature isWhich feature is alongalong another feature (for example, The bus route follows along theanother feature (for example, The bus route follows along thestreet network.)?.street network.)?.


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GeoreferencingGeoreferencing : Assigning map coordinates and: Assigning map coordinates and

spatial location All the elements in a map layer have aspatial location All the elements in a map layer have aspecific geographic location and extent that enablesspecific geographic location and extent that enablesthem to be located on or near the earth's surface. Thethem to be located on or near the earth's surface. Theability to accurately describe geographic locations isability to accurately describe geographic locations iscritical in both mapping and GIS. This process iscritical in both mapping and GIS. This process is

called georeferencingcalled georeferencing ..

Georeferencing andGeoreferencing andcoordinate systemscoordinate systems


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Describing the correct location and shape of featuresDescribing the correct location and shape of featuresrequires a framework for defining real-world locations. Arequires a framework for defining real-world locations. Ageographic coordinate system is used to assign geographicgeographic coordinate system is used to assign geographiclocations to objects. A global coordinate system of latitude-locations to objects. A global coordinate system of latitude-longitude is one such framework. Another is a planar orlongitude is one such framework. Another is a planar orCartesian coordinate system derived from the globalCartesian coordinate system derived from the globalframework.framework.

Maps represent locations on the earth's surface using grids,Maps represent locations on the earth's surface using grids,graticules, and tic marks labeled with various groundgraticules, and tic marks labeled with various groundlocations, both in measures of latitude-longitude and inlocations, both in measures of latitude-longitude and inprojected coordinate systems (such as UTM meters). Theprojected coordinate systems (such as UTM meters). Thegeographic elements contained in various map layers aregeographic elements contained in various map layers aredrawn in a specific order (on top of one another) for thedrawn in a specific order (on top of one another) for thegiven map extent.given map extent.

GIS datasets contain coordinate locations within a global orGIS datasets contain coordinate locations within a global orCartesian coordinate system to record geographic locationsCartesian coordinate system to record geographic locationsand shapes.and shapes.

G f i dG f i d


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Latitude and longitude :Latitude and longitude :One method for describing the position of a geographic locationOne method for describing the position of a geographic locationon the earth's surface is using spherical measures of latitudeon the earth's surface is using spherical measures of latitudeand longitude. They are measures of the angles (in degrees)and longitude. They are measures of the angles (in degrees)from the center of the earth to a point on the earth's surface.from the center of the earth to a point on the earth's surface.

This reference system is often referred to as a geographic This reference system is often referred to as a geographiccoordinate system.coordinate system.


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Latitude angles are measured inLatitude angles are measured ina north-south direction. Thea north-south direction. Theequator is at an angle of 0.equator is at an angle of 0.Often, the northern hemisphereOften, the northern hemispherehas positive measures of has positive measures of latitude and the southernlatitude and the southernhemisphere has negativehemisphere has negativemeasures of latitude. Longitudemeasures of latitude. Longitudemeasures angles in an east-westmeasures angles in an east-westdirection. Longitude measuresdirection. Longitude measuresare traditionally based on theare traditionally based on thePrime Meridian, which is anPrime Meridian, which is animaginary line running from theimaginary line running from theNorth Pole through Greenwich,North Pole through Greenwich,England, to the South Pole. ThisEngland, to the South Pole. Thisangle is Longitude 0. West of theangle is Longitude 0. West of thePrime Meridian is often recordedPrime Meridian is often recordedas negative Longitude, and eastas negative Longitude, and eastis recorded as positive. Foris recorded as positive. Forexample, the location of Losexample, the location of LosAngeles, California, is roughlyAngeles, California, is roughlyLatitude plus 33 degrees, 56Latitude plus 33 degrees, 56minutes and Longitude minusminutes and Longitude minus118 degrees, 24 minutes.118 degrees, 24 minutes.


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Although longitude and latitude can locate exact positions onAlthough longitude and latitude can locate exact positions on

the surface of the globe, they are not uniform units of measure.the surface of the globe, they are not uniform units of measure.Only along the equator does the distance represented by oneOnly along the equator does the distance represented by onedegree of longitude approximate the distance represented bydegree of longitude approximate the distance represented byone degree of latitude. This is because the equator is the onlyone degree of latitude. This is because the equator is the onlyparallel as large as a meridian. (Circles with the same radius asparallel as large as a meridian. (Circles with the same radius asthe spherical earth are called great circles. The equator and allthe spherical earth are called great circles. The equator and allmeridians are great circles.)meridians are great circles.)

Above and below the equator, the circles defining the parallelsAbove and below the equator, the circles defining the parallelsof latitude get gradually smaller until they become a single pointof latitude get gradually smaller until they become a single pointat the North and South Poles, where the meridians converge. Asat the North and South Poles, where the meridians converge. Asthe meridians converge toward the poles, the distancethe meridians converge toward the poles, the distancerepresented by one degree of longitude decreases to zero. Onrepresented by one degree of longitude decreases to zero. Onthe Clarke 1866 spheroid, one degree of longitude at thethe Clarke 1866 spheroid, one degree of longitude at theequator equals 111.321 km, while at 60 latitude, it is onlyequator equals 111.321 km, while at 60 latitude, it is only55.802 km. Since degrees of latitude and longitude don't have a55.802 km. Since degrees of latitude and longitude don't have astandard length, you can't measure distances or areasstandard length, you can't measure distances or areasaccurately or display the data easily on a flat map or computeraccurately or display the data easily on a flat map or computerscreen. Performing GIS analysis and mapping applicationsscreen. Performing GIS analysis and mapping applicationsrequires a more stable coordinate framework, which is providedrequires a more stable coordinate framework, which is providedby projected coordinate systems.by projected coordinate systems.

M j i i C iM j ti i C t i


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Map projections using CartesianMap projections using CartesiancoordinatescoordinatesProjected coordinate systems are any coordinateProjected coordinate systems are any coordinatesystem designed for a flat surface such as asystem designed for a flat surface such as aprinted map or a computer screen.printed map or a computer screen.

2D and 3D Cartesian coordinate systems provide2D and 3D Cartesian coordinate systems providethe mechanism for describing the geographicthe mechanism for describing the geographiclocation and shape of features using x and ylocation and shape of features using x and yvalues (and, as you will read later, by usingvalues (and, as you will read later, by usingcolumns and rows in rasters).columns and rows in rasters).

The Cartesian coordinate system uses two axes: The Cartesian coordinate system uses two axes:one horizontal (x), representing east-west, andone horizontal (x), representing east-west, andone vertical (y), representing north-south. Theone vertical (y), representing north-south. Thepoint at which the axes intersect is called thepoint at which the axes intersect is called theorigin. Locations of geographic objects areorigin. Locations of geographic objects aredefined relative to the origin, using the notationdefined relative to the origin, using the notation(x,y), where x refers to the distance along the(x,y), where x refers to the distance along the

horizontal axis, and y refers to the distancehorizontal axis, and y refers to the distancealong the vertical axis. The origin is defined asalong the vertical axis. The origin is defined as(0,0).(0,0).

In the illustration below, the notation (4, 3)In the illustration below, the notation (4, 3)records a point that is four units over in x andrecords a point that is four units over in x andthree units up in y from the origin.three units up in y from the origin.


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3D coordinate systems3D coordinate systemsIncreasingly, projected coordinate systemsIncreasingly, projected coordinate systemsalso use a z value to measure elevationalso use a z value to measure elevationabove or below mean sea level.above or below mean sea level.

In the illustration below, the notation (2, 3,In the illustration below, the notation (2, 3,4) records a point that is two units over in x4) records a point that is two units over in xand three units in y from the origin andand three units in y from the origin andwhose elevation is 4 units above the earth'swhose elevation is 4 units above the earth'ssurface (such as 4 meters above mean seasurface (such as 4 meters above mean sealevel).level).

f


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Elements of geographicElements of geographicinformationinformation

Universal principles that provide the foundation for how GIS systemsUniversal principles that provide the foundation for how GIS systemsrepresent, operate on, manage, and share geographic information.represent, operate on, manage, and share geographic information.Purpose: to provide you with a solid foundation for understandingPurpose: to provide you with a solid foundation for understandingthese key concepts and how Argils employs them.these key concepts and how Argils employs them.

Like a map, a GIS is layer based. And like the layers in a map, GISLike a map, a GIS is layer based. And like the layers in a map, GISdatasets represent collections of individual features with theirdatasets represent collections of individual features with theirgeographic locations and shapes as well as with descriptivegeographic locations and shapes as well as with descriptiveinformation stored as attributes.information stored as attributes.

There are four fundamental types of geographic representations: There are four fundamental types of geographic representations:

Features (collections or points, lines, and polygons)Features (collections or points, lines, and polygons)

AttributesAttributes

ImageryImageryContinuous surfaces (such as elevation)Continuous surfaces (such as elevation)

All the rich GIS behavior for representing and managing geographicAll the rich GIS behavior for representing and managing geographicinformation is based on these fundamental types.information is based on these fundamental types.


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Features - Points, lines, and polygonsFeatures - Points, lines, and polygonsGeographic features are representations of thingsGeographic features are representations of thingslocated on or near the surface of the earth. Geographiclocated on or near the surface of the earth. Geographicfeatures can occur naturally (such as rivers andfeatures can occur naturally (such as rivers andvegetation), can be constructions (such as roads,vegetation), can be constructions (such as roads,pipelines, wells, and buildings), and can bepipelines, wells, and buildings), and can besubdivisions of land (such as counties, politicalsubdivisions of land (such as counties, politicaldivisions, and land parcels).divisions, and land parcels).

geographic featuresgeographic features are most commonlyare most commonlyrepresented as points, lines, and polygons.represented as points, lines, and polygons.

PointsPoints define discrete locations of geographic featuresdefine discrete locations of geographic featurestoo small to be depicted as lines or areas, such as welltoo small to be depicted as lines or areas, such as well

locations, telephone poles, and stream gauges. Pointslocations, telephone poles, and stream gauges. Pointscan also represent locations such as address locations,can also represent locations such as address locations,GPS coordinates, or mountain peaks.GPS coordinates, or mountain peaks.


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LinesLines represent the shape and location of geographicrepresent the shape and location of geographicobjects too narrow to depict as areas (such asobjects too narrow to depict as areas (such asstreet centerlines and streams). Lines are alsostreet centerlines and streams). Lines are alsoused to represent features that have length butused to represent features that have length butno area such as contour lines andno area such as contour lines andadministrative boundaries. (Contours areadministrative boundaries. (Contours areinteresting, as you'll read later on, becauseinteresting, as you'll read later on, becausethey provide one of a number of alternativesthey provide one of a number of alternativesfor representing continuous surfaces.)for representing continuous surfaces.)

Polygon:Poly gon:are enclosed areas (many-sided figures) thatare enclosed areas (many-sided figures) thatrepresent the shape and location of represent the shape and location of homogeneous features such as states,homogeneous features such as states,counties, parcels, soil types, and landusecounties, parcels, soil types, and landusezones. In the example below, the polygonszones. In the example below, the polygonsrepresent parcels.represent parcels.


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AttributesAttributes ::

Maps convey descriptive information through mapMaps convey descriptive information through mapsymbols, colors, and labels.symbols, colors, and labels.Examples:Examples:

Roads are displayed based on their road class (forRoads are displayed based on their road class (forexample, line symbols representing divided highways,example, line symbols representing divided highways,main streets, residential streets, unpaved roads, andmain streets, residential streets, unpaved roads, andtrails).trails).

Streams and water bodies are drawn in blue to indicateStreams and water bodies are drawn in blue to indicatewater.water.

City streets are labeled with their name and often someCity streets are labeled with their name and often someaddress range information.address range information.

Special point and line symbols denote specific featuresSpecial point and line symbols denote specific featuressuch as rail lines, airports, schools, hospitals, and specialsuch as rail lines, airports, schools, hospitals, and specialfacilities.facilities.


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In a GIS,In a GIS, descriptive attributesdescriptive attributes are managed in tables,are managed in tables,which are based on a series of simple, essential relationalwhich are based on a series of simple, essential relationaldatabase concepts. Adatabase concepts. A relational databaserelational database provides aprovides asimple, universal data model for storing and working withsimple, universal data model for storing and working withattribute information. DBMSs are inherently open becauseattribute information. DBMSs are inherently open because

their simplicity and flexibility enables support for a broadtheir simplicity and flexibility enables support for a broadrange of applications.range of applications.Key relational concepts includeKey relational concepts includeDescriptive data is organized into tables.Descriptive data is organized into tables.

Tables contain rows.Tables contain rows.

All rows in a table have the same columns.All rows in a table have the same columns.

Each column has a type such as integer, decimalEach column has a type such as integer, decimalnumber, character, date, and so on.number, character, date, and so on.A series of relational functions and operators (SQL) isA series of relational functions and operators (SQL) is

available to operate on the tables and their dataavailable to operate on the tables and their dataelements.elements.


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Imagery :Imagery :Aerial imagery is a raster data structure obtained from variousAerial imagery is a raster data structure obtained from varioussensors carried in satellites and aircraft.sensors carried in satellites and aircraft.

Imagery is managed as a raster data type composed of cellsImagery is managed as a raster data type composed of cellsorganized in a grid of rows and columns. In addition to the maporganized in a grid of rows and columns. In addition to the mapprojection, the coordinate system for a raster dataset includesprojection, the coordinate system for a raster dataset includesits cell size and a reference coordinate (usually the upper left orits cell size and a reference coordinate (usually the upper left orlower left corner of the grid).lower left corner of the grid).

These properties enable a raster dataset to be described by a These properties enable a raster dataset to be described by aseries of cell values starting in the upper left row. Each cellseries of cell values starting in the upper left row. Each celllocation can be automatically located using the referencelocation can be automatically located using the referencecoordinate, the cell size, and the number of rows and columns.coordinate, the cell size, and the number of rows and columns.


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Typical image sources include cameras capable of capturing Typical image sources include cameras capable of capturingaerial photographs that can be georeferenced and corrected toaerial photographs that can be georeferenced and corrected to

ground locations (such as digital orthophotography).ground locations (such as digital orthophotography).


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Imagery is also used to collect data in both the visible andImagery is also used to collect data in both the visible andnonvisible portions of the electromagnetic spectrum. Onenonvisible portions of the electromagnetic spectrum. Onesystem is the multispectral scanner carried in LANDSATsystem is the multispectral scanner carried in LANDSAT

satellites that records imagery in sevensatellites that records imagery in seven bandsbands (or ranges)(or ranges)along the electromagnetic spectrum. The measures foralong the electromagnetic spectrum. The measures foreach band are recorded in a separate grid. The stack of each band are recorded in a separate grid. The stack of seven grids makes up a multiband image.seven grids makes up a multiband image.


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SurfacesSurfaces : A surface describes an occurrence that: A surface describes an occurrence thathas a value for every point on the earth. For example,has a value for every point on the earth. For example,

surface elevation is a continuous layer of values forsurface elevation is a continuous layer of values forground elevation above mean sea level for the entireground elevation above mean sea level for the entireextent of the dataset. Other surface type examplesextent of the dataset. Other surface type examplesinclude rainfall, pollution concentration, andinclude rainfall, pollution concentration, andsubsurface representations of geological formations.subsurface representations of geological formations.

With continuous datasets, it is impossible toWith continuous datasets, it is impossible torepresent all values for all locations. Variousrepresent all values for all locations. Variousalternatives exist for representing surfaces usingalternatives exist for representing surfaces usingeither features or rasters.either features or rasters.E-gE-gContour linesContour lines Isolines represent locations having anIsolines represent locations having anequal value, such as elevation contours.equal value, such as elevation contours.


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Contour bandsContour bands The areas whereThe areas wherethe surface value is within athe surface value is within aspecified range, such as bands of specified range, such as bands of average annual rainfall between 25average annual rainfall between 25

CM and 50 CM per yearCM and 50 CM per year ..

Raster datasetsRaster datasets A matrix of cellsA matrix of cellswhere each cell value represents awhere each cell value represents ameasure of the continuous variable.measure of the continuous variable.For example, digital elevationFor example, digital elevationmodels (DEMs) are frequently usedmodels (DEMs) are frequently usedto represent surface elevation.to represent surface elevation.

TIN layers TIN lay ers A Triangulated IrregularA Triangulated IrregularNetwork (TIN) is a data structure forNetwork (TIN) is a data structure forrepresenting surfaces as arepresenting surfaces as aconnected network of triangles.connected network of triangles.Each triangle node has an x,yEach triangle node has an x,ycoordinate and a z or surface value.coordinate and a z or surface value.

S ti l l ti hi dSpatial relationships and


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Spatial relationships andSpatial relationships andbehaviorbehavior

gis geographical information system presented by: madam

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