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Lecture 3
How does GIS work
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How does GIS work?Maps are stored in computers
Databases and Tables
Geometry
Attributes
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How does GIS work?Categories of reality are divided into layers
Countries, States, Cities
Parcels of land ownership
Roads, Rivers, Lakes, Buildings
ZIP codes
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How does GIS work?Layers are made up of points, lines, or polygons
Cities – points
Roads – lines
Counties – polygons
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Drawing maps Points, lines, polygons, and text
Main Street
Home
Work
Construction
Mall
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Change street layer color and thickness
Main Street
Home
Work
Construction
Mall
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Turn Streets layer off
Main Street
Home
Work
Construction
Mall
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World country layer - polygons
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Amelia Earhart’s last flight - lines
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Cities (fuel stops) - points
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Levels of geography Country State County City
DEMO
http://www.marshallco.org/www/maps/images/50seregexpl.jpg
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Levels of geography Block group
http://www2.lib.udel.edu/subj/maps/internet/dedo/nnccinc.htm
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Levels of geography ZIP code
http://cssr.berkeley.edu/cwscmsreports/maps/showEntriesCountymap.asp?page=Ora
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Levels of geography Parcel Buildings Houses
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GIS links attribute and spatial data Each layer has a database table Each map feature has one record in the table The table has attributes about the features
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One to one: layer and table One to one: map feature and record
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Is your data spatial? >80 percent of all data has location “What’s your ZIP code”
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My customer database
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ArcMap puts customers on the map
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Before GIS Just Pens and Paper
http://www.census.gov/pubinfo/www/photos/img/lowres/Hist08l.jpg
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GIS Power Just a database Tools Analysis GIS Science and Geography Geo Statistics Aids in decision making
Remember “Maps Communicate”
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Which 8% of 7000 stores to close?
http://money.cnn.com/news/specials/storysupplement/starbucks_closings/CA.html
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Where can we add new stores/Delis?
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Where can we add new stores/Delis?
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5 steps to GIS analysis
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5 steps to GIS analysis Frame the question Get the data Choose analysis method Process the data Look at the results
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Frame the question Where can we put a garbage dump?
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Frame the question Where can we put a garbage dump?
Not on bad soil Out of the city Not in a park Not in a protected area like a forest More?
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Get the data
SOILS
PARKS
URBAN
FOREST
Color in the unacceptable areas Can’t locate in dark areas
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Choose analysis method
SOILS PARKSURBAN FOREST
OVERLAY the layers on top of each other
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Process the data
SOILS
PARKS
URBAN
Solution mapFOREST
Color in the unacceptable areas
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Look at the results
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Check out other similar projects
http://www.ruralgis.org/conference/2004proceedings/thurs/session4/thurs_4_1_00.pdf
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Map Overlay But what about the protected rats?
SOILS
PARKS
URBAN
Solution mapFOREST
Rats
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Before GIS - Paper Computers speed the process Databases hold more information than paper Why GIS?
Faster Cheaper Easier More
http://www.census.gov/pubinfo/www/photos/img/lowres/Hist08l.jpg