Download - Data Day 2012_Fradkin_Intro to GIS
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Introduction to Data Mapping
Barry FradkinGIS Analyst
Metropolitan Area Planning CouncilFriday, January 27, 2012
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About me…
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Data Mapping
• More geographic data becoming available
• See patterns that aren’t otherwise apparent
• What are the properties of spatial data?
• Where can we find spatial data?• How do we make maps ourselves?
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Geographic Information Systems
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Social Networking
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Population
Bostonography.com
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Transportation
Bostonography.com
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Coordinate Systems
• Cartesian Coordinate System• Geographic Coordinate System– Latitude and Longitude
• Boston42°21′28″N, 71°03′42″W42.359228, -71.061515
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Understanding Projections
• Earth is roughly spherical• Maps are 2-dimensional• Distortion is inevitable
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Types of Projections
• Mercator is common• Specialized projections
for smaller areas • For Massachusetts:
NAD 1983 State Plane Massachusetts (m or ft.)
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Data Models
• Feature geometry can be shown in two ways:
• Vector– Points, lines, polygons– Discrete objects
• Raster– Grid of cells– Continuous data
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Attributes
• The information behind the geometry• Similar to Excel or Access tables
• Types of attributes:– Nominal (text)– Ordinal (rank)– Interval (numeric)
ID NominalOrdina
lNumeri
c1 residential low 102 industrial high 700
3commerci
almediu
m14.625
4open space
very low
0.263
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Attribute Formatting
• Headers: no spaces or special characters
• UPPER CASE / lower case / Sentence Case
• Number format makes a differenceNumber Format Minimum Value Maximum Value
Short integer -32,768 32,767
Long integer −2,147,483,648 2,147,483,648
Float Many digits, decimals
Many digits, decimals
Double More digits, decimals
More digits, decimals
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Where to find the data?
• MassGIS – Office of Geographic Information–Municipalities, roads, water, land use– US Census: blocks, block groups, tracts– Air photos, elevation, impervious surface
• Data tables from state and federal gov’t.– Unique IDs can be used to join to geography
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Downloading from MassGIS
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Compile your own data
• Geocoding– Street addresses > Address Locator– Latitude/Longitude (decimal degrees)
• Digitizing–Manually draw features from air photo– Georeference an existing map image
• Join your own tables to existing geography
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Displaying the Data
• Data layers• Symbology– Colors– Point size– Line width
• Labels– Font size– Positioning
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Cartography
• All maps should have:–North Arrow–Scale Bar–Legend–Title–Date–Source
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Consider your audience
• Make text large enough to be legible• 5 to 10% of men are colorblind• Colorbrewer.org:
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GIS Software
• Online mapping tools:–MassGIS OLIVER:
http://www.mass.gov/mgis/mapping.htm–MetroBoston DataCommon:
http://metrobostondatacommon.org/– Google Maps, Google Earth,
OpenStreetMap
• Open Source Software– Quantum GIS, GRASS, SAGA
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ESRI ArcGIS
• ArcMap• ArcCatalog• ArcToolbox• ArcScene• ArcGlobe• Cheap non-profit
license available• esri.com/
nonprofit