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Exercises for Mapping and Using US Census Data

MIT GIS Services, IAP 2012

More information, including a comparison of tools available through the MIT Libraries, can be found at:

http://libraries.mit.edu/guides/types/census/tools-overview.html

Exercise 1: American Factfinder

1. Open the New American FactFinder using this link: http://factfinder2.census.gov

The left sidebar provides several ways to search for data, including by topic, geography, population

group and industry code. You are interested in looking at housing data by county for the state of

Massachusetts.

2. Click on “Geographies.” This will open a new “Select Geographies” window.

3. Under “Geographic Type,” click on “County.”

4. In the “Geography Results” box on the right, check the box next to “All counties in

Massachusetts” and click the “Add” button at the top of the box.

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5. Close the “Select Geographies” window.

This will filter your results by the geography you selected. Your geographic selection has been added to

the “Your Selections” box in the top, left. If you do not specify a geographic location before downloading

a dataset, data for the default location usually downloads, which in most cases is Alabama, since it is the

first state alphabetically. Now you are ready to choose your dataset and download the table.

6. Click on “Topics” at the left and notice that it expands to include several subcategories.

7. You are interested in housing data from Summary File 1 for the 2010 Census. Expand the

“Dataset” subcategory and click on 2010 SFI 100% data.

8. Check the box next to General Housing Characteristics: 2010 (ID = QT-H1). If you want to learn

more about any of the datasets, you can click on the “i” in the “About” column to see a sample

table and list of variables included in the dataset.

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There are buttons at the top of the “Search Results” box to both “View” and “Download” the data. You

want to view the data first and then download it. This will give you more download options.

9. Click “View.” You will see a sample table for each county in Massachusetts. When you download

the data all the counties will be included in one table.

10. Click Download. Select whatever format you would like. If you will be joining the data with GIS

boundary files, select Comma delimited format (.csv). You do not actually have to download the

data for this exercise unless you want to.

Once the data downloads, you can work with it in a spreadsheet, join it with GIS boundary files, or

transfer it to another software program.

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Exercise 2: Social Explorer

1. Access the MIT Libraries subscription version of social explorer using the following link: http://libraries.mit.edu/get/explorer

A public version of social explorer is available at: http://www.socialexplorer.com If you will be creating many maps, you can create a personal account to save images of maps online using the “Create” link in the upper right hand corner. We will not create an account for this exercise.

2. Click on the Maps tab.

The following census geographies are available:

1790-1930 = Nation

1940-2000 = Nation, state, county tract

Census 2000 also includes: block groups, zip codes, census places The following American Community Survey geographies are available:

PUMA

County

Place

Tract

Block group

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3. Click on Census 1790 – 2010.

4. Zoom into an area of your choosing and notice that you can see smaller geographic areas, such as census tracts.

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5. Change the information that is being displayed by clicking on the drop down menus in the right side bar.

6. To save the current view of you map, click on one of the squares at the bottom of the site. You can play saved maps in succession to show change over time or in different areas.

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7. Click on the file menu and notice that you can export your maps as slides in a PowerPoint

presentation or as images. You can also print your maps. You cannot export them as a shapefile for GIS. Mapping data in a GIS would require getting the appropriate shapefile from National Historical Geographic Information System (NHGIS) (http://www.nhgis.org/), then joining the table (from the reports section) with the shapefile. You do not have to export your images for this exercise.

You can create a report (tabular data) using the “report” button in the map view or the Reports tab. It is easier to define the geographic area of interest by clicking on the Reports tab, rather than using the report button in the map view.

8. Click on the Reports tab. First you will select a survey of interest. You can only select one at a time. For this exercise select the American Community Survey (ACS) 2006--2010 (5-Year Estimates).

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9. Use the drop down menu to select a geographic area. In the example below we selected all census tracts in the state of Massachusetts and added that selection to the Current Geography Selections box.

10. Click Next to proceed.

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11. Select any variables that interest you. You can choose them from the list or search by keyword. Click Show Result when you are finished.

12. Click on the tabs at the top of the results to see the different formats in which data can be

downloaded. Clicking on the Excel tab downloads the data in Excel. The Data Download tab allows you to download data as a .csv, tab-delimited and includes program files to import and label data in statistical software packages such as SAS, SPSS, and Stata. You do not have to download the data for this exercise.

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Exercise 3: Geolytics

With Geolytics software, you can export Census data directly to a GIS shapefile; you don’t have to join

the table to the shapefile in a separate step. In the Neighborhood Change Database, which is one of

several Geolytics software packages, the data for years 1970, 1980, 1990 and 2000 are recalculated and

normalized to represent the data in 2000 boundaries. You can compare across years without having to

control for changes in boundary definitions. This exercise will guide you through extracting data for

1970, 1980, 1990 and 2000. Then we’ll bring it into ArcMap to display it.

Neighborhood Change Database is just one Geolytics product. To find out what other Geolytics products

we have do an advanced search in Barton (libraries.mit.edu/barton), the libraries online catalog with

publisher = Geolytics. The Geolytics software is typically only available on the Census workstation in the

MIT GIS Lab, Rotch Library, 7-238. More information about what is included in each of the Geolytics

products and the user guides can be found online at: http://www.geolytics.com/User-Guides.asp

Step 1: Create a new request

1. Close ArcMap if it’s open.

2. Create a folder on the desktop and name it with your Kerberos ID. (Delete this before you

leave.)

3. Open the GIS folder on the desktop and launch the Neighborhood Change Database (NCDB).

In order to keep track of your files, and to prevent saving over needed data, start by creating/saving a

new request. Unless you do this step, requests are labeled as NEWREQ and are saved over at the next

request.

4. Go to File-> Save request as ->Navigate to your folder on the desktop-> and give your file a

name “NCDBdata”. Geolytics software is pretty picky about names. It should be 8 characters or

less, numbers and letters only. For the purpose of this exercise, if you are having trouble

creating a new request, you can proceed without creating one.

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Step 2: Select time period

5. Next, click on year and select “All years normalized to 2000.” This will extract data from each of

the ’70, ’80, ’90, and ’00 Censuses, and display the data within 2000 boundaries.

Step 3: Select the geography

6. Within the Area menu, select Counties. A dialog box will come up. From the States column,

select Massachusetts. All counties within Massachusetts will come up in the Counties window.

7. Select the top and bottom county numbers, then click Select between, on the lower right

corner. This will include everything on the list in the selection. Then click Done. (For

comparison’s sake, data will be at parcel level as county boundaries likely didn’t vary).

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Note: County boundaries won’t change between Censuses, but Census tracts might. In order to extract

data for all tracts within each county of MA, we’ll select County as the area, and NCDB will break the

data down by tract. Other Geolytics software packages are set up to allow you to select a subarea within

an area (e.g. all counties within a state, several block groups within a tract).

Step 4: Choose tables

8. Next we’ll choose data tables to extract. Select Counts from the top menu and a dialog box will

open. Scroll through the list to see available data and census year for each. You can browse

through the list and select individual records, search by keyword, or if you’d like a single variable

from all 4 censuses, find the variable for one census year and then do a keyword search for the

code in the Name column. We’ll use the last option.

9. In this exercise we are going to select Total occupied housing units. The variable names are

provided below.

a. OCCHU – occupied housing units

b. TOTHSUN – total housing units

10. Search for OCCHU. Click on Browse Last Search results to scroll through what was selected. To

select these as the data you will extract, click on Add Selected Counts to Report.

Because the data is provided as a raw number rather than a percentage, we’ll also extract total housing

units so we can calculate the percentage of occupied housing units per tract (We’ll do this in ArcMap).

11. Search for TOTHSUN. Click on Add Selected Counts to Report to add to the data you’ll extract.

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12. The Report Counts window will show both of the counts you selected for all four Censuses. Click

Done.

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Step 5: Run the query

13. Next run the query. Select Map from the Run menu to generate the geographic information

we’ll use in ArcMap.

If you are not planning to use the data in a GIS, you could select one of the other options, such as

summary or a DBF to use in a spreadsheet.

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Step 6: Export the map to shapefile

14. From the File menu, select Export-> to Arcview’s Shape.

15. Open the folder that you created on the desktop. You’ll see the request you saved, plus the files

you’ll need to draw the map in ArcMap. You’ll also see a Word document. The column names

used by Geolytics are very abbreviated; this document is the key to what is in each column.

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If you have never used ArcMap or you do not plan to use census data in a GIS, you may want to end

the exercise here. Otherwise, proceed to learn how to add Geolytics data to ArcMap and change the

symbology.

Step 7: Bring the data into ArcMap

16. Open ArcMap and choose a new blank document or press cancel to open a new map document.

17. Click the add data button ( ) in the top toolbar and navigate to your folder on the desktop.

Add NCDBDATA.shp.

Data from Geolytics comes without a spatial reference. This means that while it looks accurate in terms

of shape, where it is placed on the map in relation to the world is not defined. For example, your map of

MA could end up on top of Mexico on a world map. Later we’ll define the projection to correct this.

18. Click OK to dismiss the spatial reference warning.

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Step 8: Display data

19. Right click on the layer you just added to your map document and select “Properties.”

20. In the Symbology tab, select “Quantities” on the left and “Graduated colors.”

a. In the Value field, select OCCHU0.

b. In the Normalization field, select TOTHSUN0

This will calculate the number of occupied housing units as a portion of the total number of units. (i.e.

percentage of occupied housing units).

21. Click on the “label” heading at the top of the table and select “Format labels…”

22. These numbers represent a percentage, so choose “percentage” and then click “Numeric

options…” In this menu you can choose the number of decimal places you wish to display. Click

OK.

23. Because these numbers are calculated and therefore decimals, rather than already given as a

percentage, select “The number represents a fraction. Adjust it to show a percentage.”

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24. Click OK twice to view the map.

Step 9: View different years

25. To view different years, repeat the above step using OCCHU9 & TOTHSUN9, etc. To save them as

separate layers, right click on NCDBdata and select Data->Export data. Name the different

exports by the Census year.

Step 10: Define projection

26. To be able to use this layer with other data layers, you’ll need to define the projection. Data

from Geolytics uses NAD83 (North American Datum 1983).

27. Open the toolbox, by clicking on the icon.

28. Go to Data Management Tools-> Projections and Transformations ->Define Projection.

29. For Input Dataset or Feature Class, click the drop down box and select NCDBDATA.

30. Click on the box next to Coordinate system and a dialog box will come up.

31. Click on Select and another dialog box will open. Open the folder for Geographic Coordinate

Systems -> North America -> NAD1983.prj.

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32. Click Add, then click OK through the remaining dialog boxes. You’ll see a note to indicate that

tool is working.

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Step 11: Define Projection for the data frame

33. Next we need to define the projection for the background, also called the data frame.

34. From the top toolbar select View->Data Frame Properties

35. In the dialog box, navigate to Predefined-> Geographic Coordinate Systems-> North America-

>NAD 1983

It may not look like anything has changed, but if you add other data with the coordinate system defined,

it will line up appropriately.