GIS Joins Lab

This lab will teach:

• Downloading Census Bureau economic data, and joining it to shape files.  Joining databases is an important GIS concept.
• Computing areas for shape files, and population densities.
• Making maps showing a parameter

• Your best friend from high school wants to set up a dating service in your county, and wants your help doing a GIS analysis on where in the county efforts should be concentrated.  You are to pick either men or women as the target audience, and must:
  
  • Get the following data  from the SF1 data for the 2010 Census:
    • Total population
    • Male to female ratio (either overall, or an interesting age category)
    • Age distribution by gender (limit to interesting one or two interesting age categories)
  • Get at least one additional data set from the American Community Survey; you might consider one of the following. 
    • S1501 Educational Attainment
    • B08302 Time leaving home to go to work
    • B23006, Educational Attainment by Employment Status
• If you country is large, show maps of only a portion of the county.  Prepare maps showing:
  • Population of the target gender in the county.
  • Population density of the target gender in the county.
  • Ratio of men to women (or women to men) in the county, by age group if you want.
  • Your additional data set.

• Use at least two different mechanisms to show results on the maps.
  
  

  Color code by DB field	Proportional Scale Symbols

• Discussion
  • What geometry level (block, block group, or tract) would be best to use, and why?  Include a table with the number of polygons at each level for your county, and the mean and median sizes for each in both square kilometers and square miles.  For the 2000 Census, you could get data for each geometry.  For the 2010 census this is no longer true, and we can only get the tracts. Why do you think the Census Bureau no longer distributes detailed data for the blocks?  You might consider the average population for polygon at the different levels, and privacy.
  • What are the advantages and disadvantages of the different ways to display the map data (color coding and scaled symbols)?
  • Which is better, population numbers or population density, for a map of the county?  Why?
  • What names did you pick for two of the fields that were not converted?  How hard or easy was this, both in terms of the procedure, and in finding a "good" name?

• Put some of your your maps on a DEM reflectance base map. You can also subdue (Grayscale and subdue map) it if that improves the display, and you can adjust opacity for the GIS layer on top.

Data Acquisition

Data analysis:

1. Open a  map.
   • New DEM.  With a reflectance map, this provides a very nice background, but you can use any base map you want.  The TIGER edges on top might provide additional context.  You will be trying to understand where in the county things are happening, and a good base map really helps.
     •  Database: Open the tract shapefile as an overlay atop another map
   • Open shapefile map that covers just the region of the shapefile.
2. Link/join the demographic data to the shapefile with region outlines.  You must correctly match the geometry with the correct demographics (you cannot match block groups with tracts, for instance) for the ACS data.
   • In the census demographic data, the linking field is GEO_ID2, unless you renamed it.
3. Plot maps of parameters  from the "Plot" button menu on the database table display window,
   • Color code by DB field
   • Proportional symbols plotting
   • If there are tracts along the coast with 0 population, you should filter then out. Otherwise they can cause a lot of color to be wasted, since the lowest actual value should be 0 rather than the artificial 0.
4. Computations you want
   • Compute area.
   • Convert area to square miles:
     • Edit, Field arithmetic, Copy numeric field to make a new field. You could just operate on the original field, but you must be careful that the size and precision of the field will work.  In this case, square kilometers and square miles are close enough that it should work.  If you were converting square meters to square kilometers, you need a much shorter field, but probably many more decimal places.
     • Edit, Field arithmetic, Multiply field by constant (Google the conversion factor)
   • Compute ratio (e.g. population density, or male/female ratio):  Edit button,  Field arithmetic, Quotient 2 Fields (ratio)
   • Get the mean and median of the area field with Stats, Moments, or Double clicking on field name and picking Field stats.
5. Double click on the area field header, and get Field statistics (min, max, mean, etc.)  Make a table with this information
6. Adjust the color in the underlying map to de-emphasize the background and let this data dominate, but the background helps the viewer locate the points of interest.
   • Grayscale and subdue map

CSV file import problems

Last revision 1/30/2017