Introduction to Data Mapping

Barry FradkinGIS Analyst

Metropolitan Area Planning CouncilFriday, 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.com

Transportation

Bostonography.com

Coordinate Systems

• Cartesian Coordinate System• Geographic Coordinate System– Latitude and Longitude

• Boston42°21′28″N, 71°03′42″W42.359228, -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 NominalOrdina

lNumeri

c1 residential low 102 industrial high 700

3commerci

almediu

m14.625

4open space

very low

0.263

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

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