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GIS for Resource Assessment ManagementDr.R.JaganathanDeartment of GeographyUniversity of MadrasChennai-600005We Live in Two WorldsSelf-RegulatingManagedNatural WorldConstructed World. . . These Are Increasingly In Conflict WatershedsCommunitiesNeighborhoodsDistrictsContext and ContentPatternsLinkagesTrends

Seeing the WholeManaging Places

Cartography is the art, science, and technology of making maps, together with their study as scientific documents and works of artMapsA graphic depiction of all or part of a geographic realm in which the real-world features have been replaced by symbols in their correct spatial location at a reduced scale.

power lineCartography and MapsCARTOGRAPHIC BASICSWhere am I?How far to my destination?In what direction do I go?How large?What shape?

Map function in GISStorageTemporary communicationIntermediate check of dataFinal reportTo be effective, must be correctly designed and constructed.For what tasks do we use maps?What is the role of maps in these tasks?What is necessary to answer a question?

7The Market for MapsAbout 80% of all decisions are linked to space and time:How do I get from here to the train station?How much paint do I need to buy?Where should a new airport be built?Where does Severe acute respiratory syndrome (SARS)originate?Which city has the lowest crime rate? ...

7April 22, 2003Digital Cartography - Class 18Map use is communicationWe communicate (and lie!) with maps

how do I say what to whom?

Maps provide information for some tasks or questions of some users8April 22, 2003Digital Cartography - Class 19

perceptionprimary modelmappingmap readingsecondary modelrealityCommunication with MapsCommunication in MapsMapMapReadAnalyzeInterpret

Map UserSymbolizeSimplifyClassifySelectRecognizeCartographerGIS/CAD specialist

ImageMentalimageof reality

CompileReality.The geographicenvironment

Cartography and GISFuture of cartographyVirtual maps:A truly digitized world.Official base maps and datasets available for everyone to use.3-D maps.Animated maps.

What is Spatial Data?the data or information that identifies the geographic location of features and boundaries on EarthSpatial Reference SystemMapsImageryGeographyScale Time

Can be known also as geospatial data or geographic information it is the data or information that identifies the geographic location of features and boundaries on Earth, such as natural or constructed features, oceans, and more. Spatial data is usually stored as coordinates and topology, and is data that can be mapped

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GIS/LIS Geographic/Land Information Systemsis a facility for preparing, presenting,and interpreting facts that pertain to the surface of the earthWeb MappingGoogle Earth/Open Street MapsINSPIRE/SDICrowd Sourcing

C.Dana Tomlin's definition, from Geographic Information Systems and Cartographic Modeling (Englewood Cliffs, NJ: Prentice-Hall,1990), page xi: "A geographic information system is a facility for preparing, presenting, and interpreting facts that pertain to the surface of the earth. This is a broad definition . . . a considerably narrower definition, however, is more often employed. In common parlance, a geographic information system or GIS is a configuration of computer hardware and software specifically designed for the acquisition, maintenance, and use of cartographic data."

Ian mcharg landscape architect used mylar maps to overlay different themes in 50s and 60s percursor to modern gis. RogerTomlinson in Canada in 60s. 1856 map of John Snows outbreak of Cholera in London. Bahamas example of gis spatial analysis

This is the definition I like best as at its highest level it speaks to the true essence of GIS14

What is Geographical Information?Spatial informationBetween 70 and 80% of the digital information is spatially related.Can be placed on a map.Tools to deal with this information are consequently very useful.Reveal information that was previously hidden.DestinationCustomer addressesStore / factory / warehouse locationCensus informationEnvironmental informationResource locationWhat is Geographical Information?Spatially relatedCan be assigned coordinates or any spatial reference.On the surface of the earth.Involves location and organization.ScaleCan be from general to specific.Simple to complex.A satellite can generate imagesDynamicsSpatial dynamics (variations in space).Temporal dynamics (variations in time).Coordinate systemScaleTime 1Time 2

What is a GIS?FieldsRecordsGeographicInformation SystemGeographic Information SystemEncodingWhat is a GIS?Information SystemsInformation system specializing in the input, storage, manipulation, analysis and reporting of geographical (spatially related) information.ManagementReportingAnalysisDigitizing mapsEncoding spatial data (census, vegetation, topography, etc)Geographic database in aspatial data formatSpatial analysisThematic maps19Spatial Data Objects PointLinePolygon19Data modelling - Step 2It is now important to identify these features into three categories: point, line or polygon

QuestionIdentify the following features using one of these categories for each

FeatureCategoryBuildingsRoad centrelinesLamp columnsGas pipesCTV Access coversRoad surfaces

Remember that as you continue to model the spatial data, you will move further away from the physical representation of the feature (Heywood et al 1998)

States

RoadsCapitalsRivers Lakes Representation of Geographical Information in a GIS1

Air Photos

Streets

BuildingsComponents of a GISGISPeople

Software

Hardware

Procedures

21Data Representation in GISA data model is the method used to represent real world objects in a computerTwo common methods are used:Vector data modelRaster data model22

Raster Vector Real WorldData Representation23Vector Data ModelAbstract spatial featuresPointLineArea (polygon)Record coordinatesGood for representing clearly defined objectsSpatial relationships can be defined

24Raster Data ModelRegular grid of cellsEach cell represents an area on the groundSpatial resolutionValue assigned to cell represents attributeReflectance Land coverElevationSatellite imagesDEMsGood for representing continuously changing attributes

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27Geographic Coordinate SystemsReference system for curved surface of earthNetwork of intersecting linesgraticulelongitudelatitude

28Projected Coordinate SystemReference system for features on a flat (projected) surfaceCartesian coordinate system with designated originMany different projected coordinate systemsUTMState Plane Coordinates

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Abstracting the Real World

GIS FunctionsFour broad categoriesRetrieval/classification/measurementOverlay analysisBuffering techniquesNetwork analysisGeocodingSurface analysis

32Retrieval: Selective SearchAddresses selected because they fall within circle

33The simplest spatial query can be performed on screen using the selection tools that are provided with the GIS software. For instance, you can draw a circle on screen and select all objects falling inside it. This example shows addresses that have been selected because they fall within the circle.

Reclassification (Vector)Dissolving to aggregatepolygons

34Figure 4.4: Dissolving to aggregate polygonsAnother option occurs where a user wants to create aggregate polygons from a more detailed layer. An example of this might be where a user has a polygon layer where each polygon represents a farmer's field with attribute data that includes crop type. If the user is only interested in where particular crops are grown then many field boundaries represent redundant information that can be removed. This is done by what is called a dissolve operation whereby the boundaries of adjacent polygons with the same crop type are removed to form aggregate polygons. This is shown in Figure 4.4.

Reclassify by Area Size

Work with areas > 80 acres35Source: http://www.iwr.msu.edu/edmodule/gis/reclssc.html (Institute of Water Research, Michigan State University)Size reclassification allows polygons to be selected based on their area. For linear features, overall length may be used as the selection criterion.

Reclassify by Contiguity

Work with individual forest stands, rather than the class forest as a whole.36Source: http://www.iwr.msu.edu/edmodule/gis/reclssc.html (Institute of Water Research, Michigan State University)The contiguity function allows raster GISs to analyze all examples of a particular class (eg., all forest patches) or to operate on the individual examples of that class of data (eg., any particular forest stand).Contiguity reclassification identifies 'clumps' of raster cells having the same thematic value. Each new clump is assigned a unique value.

Reclassify values

Work with elevations between 20 and 40 feetChange feet to metersVector Distance Operation: Buffers & Setbacks

Diagram of simple buffers and a setback. NOTE: buffers go outward from lines or areas; setbacks run inside of areas (not lines).38Buffer: A zone constructed outward from an isolated object (point or line) to a specific distance.Setback: A zone inside a POLYGON constructed by a fixed distance from the edge of the polygon; typically used to restrict building or activities too close to the edge of a property parcel.Buffer Creation: Illustrated

Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 60. fig. 6-3.Overlay FunctionsArithmeticaddition, subtraction, division, multiplicationLogicalfind where specified conditions occur (and, or, >,