Geo-Spatial Analysis, Part II

Data Literacy

Geospatial Analysis

• Recap:
  • All Data is summary.
  • All Data is biased.
• If we do Data right, it will not obscure what we are looking for.

Geo-Spatial Analysis

• Now let’s learn what we can do with space and place.

Simple Geography Types

• Feature: One entity on the map.
• Point
  • A single point in space. (long, lat): (0,0)
• Line
  • A connected sequence of points. [(long, lat), (long, lat)]: [(0.0), (0,1), (1,1)]
• Polygon
  • A closed shape defined by a sequence of points. [(long, lat), (long, lat), (long, lat)]: [(0,0), (0,1), (1,1), (1,0)]

Examples

<Figure size 960x768 with 0 Axes>

Examples cont.

Complex Geography Types

• Multi-points
  • Many points that combine to create one feature
• Multi-Lines
  • Multiple lines that combine to create one feature
• Multi-Polygons
  • Multiple Polygons that combine to create one feature.

Examples, cont.

How can we use these to make sense of data.

• We can assign data to these features.
• Three main files:
  • Shape File (.shp) (created by ESRI)
  • GeoJSON (.json / .geojson) (for the Web)
  • CSV (csv)
• Attach population to zip code polygons.
• Attach income levels to zip code polygons

How do we answer questions?

• Layer features on top of one another.
• Calculate overlapping, contains, etc.
• Calculate distance from other features.

Example: Peet’s Coffee

• Get Zip code polygon features (US census, NCOne Map, etc.)
• Get income levels for zip codes (US census)
• Get population levels for zip codes.
• Get locations of Starbucks (Open Street Map, Overpy, etc.)
• Calculate zip code population density.
• Calculate zip code Starbucks density.
• Select zip codes with high income levels, high population density, low Starbucks density.

Example as a group.

Where to get Geospatial Data?

• NHGIS (National Historical Geographic Information System)
• Open Data
• Open Street Map Data
• Tiger/Line Shapefiles from the Census.gov site