Visualizing data on geographical maps

Data Visualization in Tableau

Agata Bak-Geerinck

Senior Data Analyst, Telenet

The digital cartography

Digital cartography: construction and use of computer-based systems for the practice of cartography and its applications.

  • From paper maps to digital mapping
  • Beyond 2D pictures, into "virtual world"
  • GPS navigation systems
  • GIS: geographic information system
  • New professions:
    • GIS developers
    • Location Intelligence experts

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A hand placing a pin on a map

Data Visualization in Tableau

Basic (digital) geometries

  • Point: an exact location on the space

    • Requires X, Y coordinates
    • (optional) Z coordinate indicates height

  • Line: "polygonal chain", sequence of points

    • Requires a set of sequential points

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  • Polygon: a plane figure described by a finite number of line segments
    • Requires a set of lines (polygonal chains)
    • Starting and closing point

Example of basic geometries

1 Picture: https://en.wikipedia.org/wiki/GeoJSON
Data Visualization in Tableau

Various (geographical) spatial data types

Plain text/spreadsheet files:

Example of lat/long coordinates on the map

  • Latitude/Longitude e.g. 19.25 and 99.8
  • Names and codes, e.g., US, London but also (airport) LAX or (NUTS$^1$) BE231 in Europe

Spatial files (e.g. Shapefile or GeoJSON)

Example of lat/long coordinates on the map

  • An object containing information about the specific geometry (e.g., point, line, polygon, etc.) along with optional metadata
1 NUTS = Nomenclature of territorial units for statistics
Data Visualization in Tableau

Recognizing the fields as geographical data

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  • Assigning a correct geographic role to fields
  • Tableau map server auto generates latitude/longitude information
  • Double-check the spelling, and number formatting:
    • Lat/Long require numeric, decimal data
    • Correcting typos/ alternative spelling
    • Upload custom geocoding file, if needed

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Example of assigning a Geo role to a field in Tableau

Data Visualization in Tableau

Working with GeoJSONs

Example of GeoJSON

1 https://geojson.io/
Data Visualization in Tableau

Airbnb dataset

Snapshot of Inside Airbnb data dashboard

1 http://insideairbnb.com/barcelona
Data Visualization in Tableau

Let's practice!

Data Visualization in Tableau

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