Introduction to Data
Mapping
Barry Fradkin
GIS Analyst
Metropolitan Area Planning Council
Friday, January 27, 2012

About me…

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?

Geographic Information Systems

Social Networking

Population
Bostonography.c

Transportation
Bostonography.c

Coordinate Systems
• Cartesian Coordinate System
• Geographic Coordinate System
– Latitude and Longitude
• Boston
42°21′28″N, 71°03′42″W
42.359228, -71.061515

Understanding Projections
• Earth is roughly spherical
• Maps are 2-dimensional
• Distortion is inevitable

Types of Projections
• Mercator is common
• Specialized projections for
smaller areas
• For Massachusetts: NAD
1983 State Plane
Massachusetts (m or ft.)

Data Models
• Feature geometry can be shown in two ways:
• Vector
– Points, lines, polygons
– Discrete objects
• Raster
– Grid of cells
– Continuous data

Attributes
• The information behind the geometry
• Similar to Excel or Access tables
• Types of attributes:
– Nominal (text)
– Ordinal (rank)
– Interval (numeric)
ID Nominal Ordinal Numeric
1 residential low 10
2 industrial high 700
3 commercial medium 14.625
4 open space very low 0.263

Attribute Formatting
• Headers: no spaces or special characters
• UPPER CASE / lower case / Sentence Case
• Number format makes a difference
Number 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

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

Downloading from MassGIS

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

Displaying the Data
• Data layers
• Symbology
– Colors
– Point size
– Line width
• Labels
– Font size
– Positioning

Cartography
• All maps should have:
–North Arrow
–Scale Bar
–Legend
–Title
–Date
–Source

Consider your audience
• Make text large enough to be legible
• 5 to 10% of men are colorblind
• Colorbrewer.org:

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

ESRI ArcGIS
• ArcMap
• ArcCatalog
• ArcToolbox
• ArcScene
• ArcGlobe
• Cheap non-profit
license available
• esri.com/nonprofit