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Faculty of Engineering Technology

Building and Construction Sciences

EA141 Module 7

Geographic Information SystemsGIS

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7.1 Information Systems

• collection of raw data• processed• to produce useful information

• Steps observation collection processing (analysis) results decisions

e.g. test marks

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7.2 Geographic Information Systems

• geographic data = location (x,y,z,t) of: people places things

• all info in a GIS must be geographically refererenced

• temporal referencing much more difficult!

• processing = spatial analysis

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7.2 GIS vs. IS

• e.g. where to locate a new donut shop? I.S. … how many donut shops there are in Hamilton G.I.S. … draw me a map showing location of all

donut shops in Hamilton

• GIS uses "spatial analysis" to produce a "smart map"

• most things we do in GIS could be done with paper maps (dumb maps)… but GIS makes it a lot easier

• time = $$$ … GIS makes new analyses feasible

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7.3 GIS and Surveying

• GIS new data acquisition

• GIS relies on accurate data

• Surveying = new data acquisition

• other fields of Geomatics also contribute: GPS photogrammetry remote sensing

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7.4 What's it made of?

• GIS = hardware (computer, printer, etc.) software (MapInfo, ArcInfo, ArcView) data

• approx. $$cost$$ breakdown: hardware 10-20% software 10-20% data 60-80%

data acquisition data entry data scrubbing

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7.5 Spatial Data

• all natural or man-made features lines or symbols on maps images on photos

• "spatial object" = digital representation of real-world "entity"

• dimensionality… 0-D = (x,y,z) = "point data" 1-D = set of point data = "line data" 2-D = closed sets of lines = "area data" 3-D = "volume data"

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7.5 Spatial Data - Dimensionality

• 0-D = (x,y,z) = "point data" = position only e.g. manhole traffic light well donut shop

• 1-D = set of point data = "line data" e.g. roads sewers property lines stream

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7.5 Spatial Data - Dimensionality

• 2-D = closed sets of lines = "area data" e.g., building footprint park wooded area land zoned "commercial"

• 3-D = "volume data" e.g., gravel quarry cut/fill area oil/gas deposit

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7.5 NON-Spatial Data

• a.k.a. "attribute data" = any other characteristics that pertain to an entity e.g. ownership soil type age of structure material

• e.g. water well spatial data = point data = 0-D = location non-spatial data = owner's name, drill date,

depth, etc.

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7.6 Data Models

• what data needs to be included in the GIS? depends on end-uses depends on budget $$$

• two types of data models Raster (dumb) = 0-D Vector (smart) = 1-D to 3-D

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7.7 Topology

• branch of math describing relationships between spatial objects

• topological relation may be: connectivity (connected to another object)

directionality (before or after another object) adjacency (beside another object) nestedness (inside another object)

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7.8 Analysis - Buffering

• common analytical function of GISs

• area around an object

• think of AutoCAD "OFFSET" command point buffer = area around a point

line buffer = area left & right of a line

polygon buffer = area around area

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7.8 Other Analyses

• adjacency e.g. find neighbouring properties

• connectivity e.g. find connected watermains, streets to

evaluate emergency preparedness

• overlay MOST COMMON ANALYSIS e.g. show all properties:

with no vegetation slope < 5% on clay soil < 15 min from a donut shop

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7.9 GIS & GPS

• GPS gives current location of mobile things

• GIS knows locations of fixed features

• GIS + GPS tells me: what route will minimize time application to emergency vehicles, police best route from where I am to a donut shop

when visiting a new city

• "the only limit is our imagination"…