3 GIS Data Structure
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Transcript of 3 GIS Data Structure
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SPATIAL & NON-SPATIAL DATA
Spatial Data
Orientation of the object
Shape
Relative position with respect to other features More importantly, defined and described by
coordinates (x,y)
Non-Spatial Known as attribute data
Length, area, density, depth of soil, lithologies
In tabular form
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SPATIAL DATA: OBJECTS IN A MAP
Lithology map & landslides distribution
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NON-SPATIAL DATA: ATTRIBUTES
Also known as attributedata
Mainly tabular data
representing rows andcolumns
Rowsrepresentingindividual samplingpoints
Columnrepresentproperties/parameterfor the respectivesampling points
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RELATIONSHIP BETWEEN SPATIAL &
NON-SPATIAL DATA
Each object isidentified bydescriptions
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DATA STRUCTURE
Data Structure
Vector Raster
Line Point Polygon
Grid
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VECTOR STRUCTURE
Also known as spaghetti model
Presented as
a)Point
b)Linec)Polygon
All three structures (point, line, polygon) are basic
topological concept
Containing coordinates
Usually accompanied with non-spatial data
Ways of input includes digitizing using manual digitising
or on screen digitising (on the fly)
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VECTOR STRUCTURE: POINT
spatial object with no
area
geographicalrepresentation of
coordinates (lat, long)
wells, landslide locations,sampling stations, electric
pole
Landslide locations
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VECTOR STRUCTURE: LINE
connected sequenceof points
no area
the line itself is not acoordinate location,but coordinate/locationalong a line is definedat a specific point
Lineaments, roads,drainage line, contourlines
Drainage
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VECTOR STRUCTURE: POLYGON
A closed area
Usually divided into
different area
Land use,
geological map,
soil map
Soil map
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TOPOLOGY IN VECTOR DATA
The way in which features in GIS are connected toeach other
Spatial relationship between features (e.g. overlap,
adjacency, connectivity
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TOPOLOGY IN VECTOR DATA
Entity Requirement
Point Geographical reference
Line Ordered set of points with define start
and end points which also give the line
direction
Area (polygon) How the line or point is connected to
define the boundary
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TOPOLOGY IN VECTOR DATA
http://www.esri.com/news/arcnews/summer02articles/arcgis83-brings.html
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REPRESENTING VECTOR DATA
emyshoran.blogspot.com
http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=eHljywu8Q4RSiM&tbnid=tjGxi_QN-CYKkM:&ved=0CAQQjB0&url=http://emyshoran.blogspot.com/2012/06/geographic-information-system.html&ei=JmF_Ub6BAYa4rgfXjoAQ&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=eHljywu8Q4RSiM&tbnid=tjGxi_QN-CYKkM:&ved=0CAQQjB0&url=http://emyshoran.blogspot.com/2012/06/geographic-information-system.html&ei=JmF_Ub6BAYa4rgfXjoAQ&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269 -
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RASTER DATA STRUCTURE
Continuous surface
Represented by pixels
Each pixel carries value
Slope angle map, slope
curvature map, elevation
map
Raster type elevation map
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TRANSFORMING VECTOR TO RASTER
Vector elevation data (contour) Raster elevation data
V t R t
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Vector on Raster
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www.automation-drive.com
http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=UyqMS-sE7oHb5M&tbnid=CeMzWPQeBmHJxM:&ved=0CAQQjB0&url=http://www.automation-drive.com/raster-data&ei=sWB_UZ3WLpHzrQeSgoGgBg&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=UyqMS-sE7oHb5M&tbnid=CeMzWPQeBmHJxM:&ved=0CAQQjB0&url=http://www.automation-drive.com/raster-data&ei=sWB_UZ3WLpHzrQeSgoGgBg&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=UyqMS-sE7oHb5M&tbnid=CeMzWPQeBmHJxM:&ved=0CAQQjB0&url=http://www.automation-drive.com/raster-data&ei=sWB_UZ3WLpHzrQeSgoGgBg&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269http://www.google.com.my/url?sa=i&rct=j&q=vector+raster+data&source=images&cd=&cad=rja&docid=UyqMS-sE7oHb5M&tbnid=CeMzWPQeBmHJxM:&ved=0CAQQjB0&url=http://www.automation-drive.com/raster-data&ei=sWB_UZ3WLpHzrQeSgoGgBg&psig=AFQjCNGokph6g-ShwybYqzy5F4ce-f30hw&ust=1367388714577269 -
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ADVANTAGE: VECTOR & RASTER
Vector Raster
Good representation of the realworld
Compact data structure
Topology can be describedAccurate graphicsRetrieval, updating andgeneralisation of graphics andattributes are possible
graphic output is easy tovisualise
No data conversion is neededGeographic location of datacan be retained
Simple data structures Overlay /combination of data
with remotely sensed data is
easy Spatial analysis is easy Simulation is easy because of
the size and shape are thesame (pixel)
Good for continuous data (e.g.elevation, slope angle)
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DISADVANTAGE: VECTOR & RASTER
Vector Raster
Complex data structureOverlay of data is difficultAnalysis is difficultUnsuitable to representcontinuous data (e.g. elevation,slope angle)
Resolution problemUnsuitable to represent linear or curvylines
Choice of resolution and problem withgeneralisation occur when convertingvector to raster
High volumes of data (the higher theresolution, the more time it takes forprocessing)
Simplification of high volume data toreduce data size will involvegeneralisation
Not as beautiful as vector in terms ofpresentation
Network linkages is hard to establish
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DATA ERROR
Terminology:
a) Error: How far is the departure/difference from the real
value
b) Accuracy: The degree of the measured data close to its
true valuec) Precision: The level of detail. 160. 153m is more precise
than 160m
d) Bias: Consistency error
e) Resolution: How well the smallest feature can be
captured in the data
f) Generalisation: the degree of simplification when
handling the data
http://www.nuim.ie/staff/dpringle/gis/gis11.pdf
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SOURCES OF DATA ERROR
a) Data Input Error
I. Primary error
The original dataset such as a hardcopy map already containingerror, therefore the input data into the GIS system will also contain
this errorII. Secondary error
Refers to the errors that occurred during the process of entering thedata
b) Data Processing Error
Conversion of vector to raster. Converting vector to raster will resultin topological error. The real representation of vector will alsochange due to the selection of cell size in the conversion process.Small features may also lost due to cell size choices
http://www.nuim.ie/staff/dpringle/gis/gis11.pdf
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SOURCES OF DATA ERROR
c) Non-spatial errorRefers to attribute error where error occurred duringdescription/name/label were mistakenly entered by user
d) Conceptual errorRefers to how different people view the real world. For example,how do you view a building in GIS, a point or polygon
e) To err is human bionic eye shaky hand perception patience intelligence distraction-your phone?
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DATA ERROR EXAMPLE : SHRINK MAP
mappinglondon.co.uk
http://www.google.com.my/url?sa=i&rct=j&q=crumpled%20maps&source=images&cd=&cad=rja&docid=k6J8SZXpS5wwnM&tbnid=LHWaTg1pEZGrwM:&ved=0CAQQjB0&url=http://mappinglondon.co.uk/2011/the-crumpled-map-of-london/&ei=aS2QUaDKOMHUrQfNkoHoBg&psig=AFQjCNFzNrGku9ILfUZIZ2RIow87UUliBA&ust=1368489665849708http://www.google.com.my/url?sa=i&rct=j&q=crumpled%20maps&source=images&cd=&cad=rja&docid=k6J8SZXpS5wwnM&tbnid=LHWaTg1pEZGrwM:&ved=0CAQQjB0&url=http://mappinglondon.co.uk/2011/the-crumpled-map-of-london/&ei=aS2QUaDKOMHUrQfNkoHoBg&psig=AFQjCNFzNrGku9ILfUZIZ2RIow87UUliBA&ust=1368489665849708 -
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EXAMPLE DATA ERROR: CONVERSION
Rasterize
Vector Raster
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EXAMPLE DATA ERROR: CONVERSION
Rasterize
http://tutor.nmmu.ac.za/uniGISRegisteredArea/Material/Module%206/Adobe%20Files/C6%20Section02.pdf
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EXAMPLE DATA ERROR: CONVERSION
Elevation in raster Contour lines
generated from raster
Original contour
lines
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Point? Polygon?
How do you
perceive a
feature
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2 lines? 1 line?
How do you
perceive a
feature
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REFERENCES
Advantage & Disadvantage of Data structure
http://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htm
Chandra, A.M. & Ghosh, S.K. 2006. Remote Sensing andgeographical information system. Alpha Science: Oxford
Bonham-Carter, G.F. 1994. Geographic InformationSystems for Geoscientists: Modelling with GIS. Ontario:Pergamon
Burrough, P.A. 1991. Principles of GeographicalInformation Systems for Land Resources Assessment.Oxford: Calendron Press
i t l i l ti l
http://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htmhttp://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htmhttp://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htmhttp://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htmhttp://planet.botany.uwc.ac.za/nisl/GIS/GIS_primer/page_19.htm