Goal: Create thematic map of PERCENT of WORKERS who DRIVE TO WORK ALONE.

Agenda:

• Overview of steps in the lab:
  • Data and computation needed to map the percent of workers driving to work alone:
  • 2010 census block group boundaries for Eastern Mass
  • Census counts for workers aged 16 and over who do/do-not drive to work alone
  • Compute percentage who drive to work alone
  • Join census percentages to block group boundaries and map thematically
  • Get the needed files into C:\temp\...
  • Extract Eastern Mass census block groups in Mass State Plane coordinates
  • Potential problems with various spatial selection methods
  • Could you select by attribute?
  • Find and extract the appropriate ACS variables at the census block group level
  • Construct your drive-to-work indicator (with appropriate block group identifier)
  • Join your drive-to-work indicator to the Eastern Mass map
• Using ACS data
  • Today's files are big enough (36 MB) to worry about organizing useful copies in C:\temp
    • Copy entire directory Q:\data\lab3_data to a LOCAL drive (e.g., C:\temp)
  • Start 11188_lab3.qgz from your local copy
  • At end of day, copy entire C:\temp\lab3_data directory (with saved QGIS projects) to I:\ or a USB drive
  • Finding the desired variable
    • What ACS variable? Using the ACS appendices and table templates
  • Normalizing counts to compute percents:  divide counts by the appropriate 'total'
  • Where to get data?
  • ACS products (and margin of error estimates)
• Some data tables are already created for your convenience!
  • Usually stored in databases, e.g., MS-Access, PostgreSQL, MySQL
    
  • Why use databases?
  • Why not use QGIS or a spreadsheet instead?
• DEMO During-lab
  • Open 11188_lab3.qgz
  • Export/import shapefiles and data tables
  • 'Select by location' options: finding block groups in certain counties
  • Construct new fields - and avoid divide by zero problems
• Data sources: Census, Social Explorer, the MIT Geodata repository, MassGIS, etc.