FREC 480 -- GIS in Natural Resource Management
Census and TIGER Data

[INTRODUCTORY NOTES: From here on you will be creating a lot of new data files. Do not use spaces or other special characters when naming files or directories. I recommend you avoid capital letters too; stick with lower-case letters, digits and the underscore character. Keep track of your files on your data stick or network drive; do not save files in "temp" directories.
At the end of each work session, save the current status of your project. A "project" file does not include your map data files; it simply references where they are stored and how they should be displayed. When saving an MXD (project) file on a data stick, you should save "relative path names" to your data (check Document Properties--Data Source Options).]

This project provides a thorough introduction to the analysis of US Census Bureau data mapped with TIGER geodata. The Constitution requires the Federal government to conduct a complete census of the US population every decade for purposes of reapportioning the US House of Representatives.  Nowadays the Census Bureau contacts every household by mail, with followup visits by enumerators.  Every household answers the questions on the "short-form" questionnaire about occupants' genders, ages, races, etc.  A large proportion of households receive a "long-form" questionnaire containing all the short-form questions plus additional questions regarding income, schooling, employment, marital status, etc.  Summary data compiled from the short-form ("100% count") questions are called Standard Format 1, or "SF1" data. Summary data compiled from the long-form ("Sample") questions are called "SF3" data.

The Census Bureau summarizes these data at various levels of geographic detail, using a hierarchy of geographic area units: states, counties, Census Tracts, Census Block Groups and Census Blocks.   The Bureau also publishes GIS data, known as TIGER (Topologically Integrated Geographic Encoding and Referencing) files, that are used to create polygon shapefiles of states, counties, Tracts, Block Groups and Blocks. Each of these is identified by a unique FIPS (Federal Information Processing Standard) code:
  • Each state is identified by a 2-digit code; Delaware is 10.
  • Each county is identified by a 3-digit code, appended to the 2-digit state code. The code for New Castle County, Delaware, is 10003.
  • Each Census Tract within a county is identified by a 6-digit code, appended to the county code. The code for the Tract in New Castle County DE that contains the center of the UD campus is 10003014502.
  • Each Block Group within a Tract is identified by a single digit, appended to the Tract code. The center of campus is Block Group 100030145022.
  • Each Block within a Block Group is identified by three more digits appended to the Block Group code. Morris Library is located in Block 100030145022003.
The Bureau releases summarized SF3 data down to the Block Group level, and summarized SF1 data down to the Block level. State-, county-, tract-, block-group- and block-level Census data tables extracted from these data files can be joined to these polygons via their matching FIPS codes.

The TIGER data also include point, line and polygon features representing roads, rail lines, streams, water polygons and other physical features.
ESRI, the publisher of ArcGIS, maintains a website  http://arcdata.esri.com/data/tiger2000/tiger_download.cfm from which you can download TIGER and associated 2000 Census data.  Access this site to download the following shapefiles for New Castle County, Delaware:
  • Census Block Groups 2000: "tgr10003grp00.shp"
  • Census Blocks 2000: "tgr10003blk00.shp"
  • Census Tracts 2000: "tgr10003trt00.shp"
  • County 2000: "tgr10003cty00.shp"
  • Line Features -- Hydrography: "tgr10003lkH.shp"
  • Line Features -- Rails: "tgr10003lkB.shp"
  • Line Features -- Roads: "tgr10003lkA.shp"
  • School Districts -- Unified: "tgr10003uni.shp"
  • Water Polygons: "tgr10003wat.shp"  
  • Also include the Census Block Demographics (SF1) -- "tgr10000sf1blk.dbf" -- in your download.

Next, download the Census Block Group demographics file that I created from the SF3 data for New Castle County. Unzip all of these files into the same project folder on your data stick or the network drive.  Using ArcCatalog, rename these shapefiles with more meaningful names ("roads," "streams," etc.). 

The TIGER shapefiles are in lat-lon decimal degrees, but they don't have accompanying projection (.prj) files that specify this, so Arc won't handle them correctly until you define the coordinate system for each shapefile. Use the Arc Toolbox's Data Management Tools--Projections and Transformations--Define Projection tool, or edit the shapefile Properties in Arc Catalog, to define each shapefile's coordinate system as "Geographic--Spheroid-Based--GRS1980."

Now load the TIGER shapefiles and SF1 Census database file into your a new ArcMap project.  In the data frame's Properties, set the Coordinate System to "Projected--State Plane--NAD 1983--Delaware" This doesn't alter the unprojected shapefiles; it just displays them in a State Plane projection like the map on the left, not like the map on the right.

  1. Create a categorical road map with different line styles for sets of Census Feature Classification Code (CFCC) categories in the Roads shapefile: A1x's are interstate highways; A2x's are main highways; A3x's are connecting roads; A4x's and higher are neighborhood roads, except A63's which are highway ramps. Group the A10's as a category, the A20's as a category, the A30's as a category, the A40's and everything else except A63's as a category, and the A63's as a category. Include the water and rail features in your map with appropriate display styles. Once you get really nice symbology set up for the roads shapefile, you can save the shapefile with its symbology as a "layer" file. (You can even save symbologies for a whole group of shapefiles in a group layer file.)

  2. Join the SF1 demographics Block-level file to the Census Blocks shapefile attribute table using the common STFID field.  Each block is identified in the STFID field by its hierarchical 15-digit FIPS code SSCCCTTTTTTBBBB where SS is the state, CCC is the county, TTTTTT is the tract and BBBB is the block ID.  (Block Groups within each Tract are identified by the first digit of the block ID.)  Likewise, join the Block-Group-level SF3 data for New Castle County to your block group shapefile using the 12-digit block group ID's (SSCCCTTTTTTB)

    Create "AREA" fields (data type should be "Double") in the block attribute table and the block group attribute table. Then right-click on the field headings and use "Calculate Geometry" to calculate the polygon areas in square meters or square kilometers (1 sq. KM = 1,000,000 sq. M.) Note that if you calculate areas from lat-lon units you get bogus measures based on "square degrees."

    Now create cool-to-hot thematic maps of 2000 population density by Census Block and by Block Group for the county using whatever classification scheme works best. 

  3. Create a dot-density map of children ages 5-17 by Census Block for just the four northern New Castle County school districts (Brandywine, Christina, Colonial and Red Clay), one dot per 5 kids, making the block boundaries transparent, overlaid on roads and water features.

    Calculate the total 2000 population of school-age children (ages 5-17) within the boundaries of each of the four northern school districts. (Select each District, then use "Select by Location" to select Census blocks that have their centroids in the selected district.) Look up total student enrollment numbers for each of these 4 school districts on the web.  Approximately what percent of the school-age population in each district attends that district's public schools?

  4. Download the public and private school point shapefiles (These are in DE State Plane NAD 1983 coordinates).

    Select the New Castle County Vo-Tech high schools from the public schools shapefile. Export these features to a separate shapefile (click on the layer in the Table of Contents frame and use Data--Export Data; do not simply export their attribute data to a separate database file). Select all the charter schools from the public schools shapefile and export these features to a separate shapefile; Start the Editor on the directory containing these shapefiles, and select and delete the vo-techs and charters from the public schools shapefile. Edit the "District" fields in the vo-tech and charter shapefiles to identify the public school district in which each of these schools is located.

    Create a graduated symbol map of the four school shapefiles, using their enrollments to determine symbol size, and adjusting each layer's symbol size range so that the sizes are reasonably consistent across the four categories of school.

    Use the Analysis Tools--Statistics--Summary Statistics tool or Select-by-Location to calculate private, vo-tech, charter and regular public school enrollment sums for Brandywine, Christina, Colonial and Red Clay school districts; create a 2-way summary table of K-12 enrollments by district by school type.

  5. You can use Arc Toolbox's Analysis--Proximity--Buffer tool to create a nicer graduated symbols map of schools' enrollments by creating buffer features around schools sized according to enrollment. Do this for each of the four school layers. Display these four buffer layers in different fill colors (no outline color) with 50% transparency, overlaid on the dot-density map of 5-to-17 year olds.

  6. (OPTIONAL:) Under Tools--Extensions activate the Spatial Analyst extension. Add the Spatial Analyst toolbar and set the Spatial Analyst Options so the Extent is the county boundary and the Cellsize is 30 (meters). Use the Distance--Allocation tool to create four sets of Thiessen polygons identifying the straight-line minimum-distance service areas for (1) the four vo-tech high schools countywide within the county vo-tech boundary (2) the charter high schools countywide; (3) the private high schools countywide; and (4) the regular public high schools within their individual district boundaries (Colonial has only one regular public high school.)

    Calculate the areas of the Theissen polygon service areas, and divide each school's enrollment by its Theissen polygon area to obain its "service density." Compare this to the spatial distributions of high-school-age kids in the Census block-group data across the service areas Identify the areas with apparent shortages of high school capacity. Create a map with the dot-density of high-school-age kids superimposed on an aggregate school capacity map derived from all four Theissen polygon maps.

  7. If you haven't already activated the Spatial Analyst extension (see above), do so now. Download the EPA's point shapefile of toxic waste sites. The "TYPE" field near the end of the attribute table identifies the "Superfund" toxic waste sites. I included a field of ones to use in creating density maps of these.

    Use the Spatial Analyst "Density" or "Interpolate to Raster--Kriging" tool to create separate density maps of the Superfund sites and all other EPA sites using a search radius of 3000 meters. Use the Raster Calculator to create a weighted-sum exposure risk map, adding 5 times the Superfund density plus the other EPA site density. Is there a spatial correlation between exposure risk and block group poverty rates?

    8. "Do the chickens have large talons?"