gis data and sources. building topography land use utility soil type roads district land parcels...
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![Page 1: GIS DATA AND SOURCES. Building Topography Land use Utility Soil Type Roads District Land Parcels Nature of Geography Objects](https://reader035.vdocuments.site/reader035/viewer/2022081515/56649d805503460f94a64388/html5/thumbnails/1.jpg)
GIS DATA AND SOURCESGIS DATA AND SOURCES
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BuildingTopographyLand use
Utility Soil Type
RoadsDistrict
Land Parcels
Nature of Geography ObjectsNature of Geography Objects
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NATURE OF SPATIAL DATANATURE OF SPATIAL DATA(GEOGRAPHIC OBJECTS)(GEOGRAPHIC OBJECTS)
• spatial component – relative position between objects– coordinate system
• attribute component– explains spatial objects characteristics
• spatial relationship– relationship between objects
• time component– temporal element
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SPATIAL DATASPATIAL DATA
SPATIAL NON-SPATIAL
JALAN JAYA
ADDRESS NAME
9, JALAN JAYA
10, JALAN JAYA LUKE
HAMID
9 10
MAP DATABASE
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SPATIAL DATA CRITERIA:SPATIAL DATA CRITERIA:
• X-Y Coordinate System
• Shape
• Area/Size
• Perimeter
• Distance
• Neighborhood
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ATTRIBUTES:ATTRIBUTES:
• Explains about spatial data
• Relevant non-spatial data
• Words or Numbers
• Qualitative methods
• Quantitative methods
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Digital data
Maps and Plans
Paper files
Photogrammetry
Remote Sensing Field survey
Interviews
GIS Data Sources
Data
Data
Data
Data
GIS
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DATA SOURCESDATA SOURCES
• Existing data– digital– map and plan– paper files
• low cost• acquisition
– remote sensing– photogrammetry– field survey
• high cost
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A B
QUERY ON DATABASE AND GRAPHICSQUERY ON DATABASE AND GRAPHICS
DATABASE
DATABASE
DATABASE
A B
A B
DATABASE TO QUERY GRAPHIC DATABASE
GRAPHICS TO GRAPHICS QUERY DATABASE
GRAPHICS TO THEME QUERY DATABASE
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AVAILABLE DIGITAL DATAAVAILABLE DIGITAL DATA
• original format sometimes need to be changed into targeted format. (See example in hand-outs.)
• data maybe built for different purposes– quality of data not known
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SPATIAL COMPONENT FROM MAPS AND SPATIAL COMPONENT FROM MAPS AND PLANSPLANS
• need to be changed into digital format– scanning– digitizing– keyboard entry
• coordinates• field survey data
• the quality of data is known and controlled
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•quality of data depends heavily on maps and plans
•key-in coordinates or survey data produces high quality data
…. SPATIAL COMPONENT FROM MAPS SPATIAL COMPONENT FROM MAPS AND PLANSAND PLANS
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Producing Digital Data
Scanning Keyboard entry Digitizing
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DATA ACQUISITIONDATA ACQUISITION
• spatial component can be obtained by– remote sensing– photogrammetry– survey
• attribute component can be obtained by– remote sensing/photogrametry – interviews– field visit
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ATTRIBUTE COMPONENTATTRIBUTE COMPONENT
• retype from maps, plans or hardcopy files• copied from existing digital data
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Attribute #1Attribute #2Attribute #3 . .Attribute #n
Attribute Component
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DATA ENTRYDATA ENTRY
• involves 75% of total implementation cost• majority of data entry methods require a lot of time
• data sharing enables lower data costs i.e. existing data
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DATA QUALITY (I)DATA QUALITY (I)
• misconception that data from GIS is of higher quality – GIS uses the latest technology
• quality of GIS information depends on quality of data– ‘garbage in garbage out’ (GIGO)
• conventional method, users decide for their own– GIS?
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Cost
Quality
Data QualityData Quality
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SPATIAL ACCURACYSPATIAL ACCURACY
• Precision - indicates how closely several positions fall in relation to each other
• Accuracy - is a measure of the closeness of one or more positions to a position that is known and defined in terms of an absolute reference system.
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ERROR SOURCES (I)ERROR SOURCES (I)
• data acquisition– device/instrument errors– data entry errors– image interpretation error
• data conversion– instrument inaccuracies– device/instrument operator– manuscript used
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ERROR SOURCES (II)ERROR SOURCES (II)
• data storage– digital representation limits– disk storage limits
• used by huge raster formats
• data processing– rounding off error
• digital representation – error propagation law
• information derived by mathematical operations no more accurate than original information