MAP, DATA & GIS LIBRARY
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Census Mapping
Quantitative Mapping using census data
This tutorial includes all necessary steps to create a thematic map using numeric census tract data – from data
acquisition; excel file formatting; preparing a boundary shape file; to the final product of designing a choropleth map.
This exercise assumes an understanding of ArcGIS software.
STEP ONE: Download census data from CHASS
1. Navigate to the University of Toronto CHASS Site http://datacentre.chass.utoronto.ca/census/ “Canadian Census
Analyser”
2. Under Census Profile Tables > by Census Geography (select Census Tract)
3. Select profile of interest or the header “2006 (cumulative)” (includes all profile data). This example uses the
Labour Market Activity profile.
4. From the listing on the left, Narrow CMA / tracted CA to Ontario. The CMA listing on the right updates to show
only Ontario CMAs.
5. Scroll down and select St.Catharines – Niagara [539](Ont.).
6. Under the Census Category heading, hold down the CTRL key while selecting the variables of interest. For the
purposes of this tutorial select the following:
 Total population 15 years and over by labour force activity – 20% sample data
 Total employed labour force 15 years & over with usual place of work or no fixed workplace address by
mode of transportation – 20% sample data
 Select ‘Car, truck, van as driver’ and ‘Public transit’ under this category
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7. Make the following selections to complete the request:
Include in the result: CTUID (CMA/CA code + CT name)
Data category to be listed as: columns
Select the output format: MS Excel ready
Click Submit Query.
The file is automatically downloaded by your Internet Browser. Open the file (default name is “census.csv”) in MS Excel.
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STEP TWO: Preparing an Excel File
1. The Excel file must be cleaned up before it can be used in ArcGIS.
2. Add appropriate field names – row 11 (DO NOT format cells of CTUID to be TEXT)
Using the descriptions for each “COL” (column), enter a truncated field name in the cells just above the data (e.g. using
row 11 in the above screenshot). Field names must begin with a letter, contain only letters, numbers and underscore
characters and be limited to 64 characters long. DO NOT INCLUDE SPACES OR SPECIAL CHARACTERS.
3. Identify ‘named range’ of cells to be added to ArcGIS by clicking the top-leftmost cell to be included (in the
above example, cell “B11”).
4. Hit F8 to begin the named range selection.
5. On the keyboard hold down CTRL and hit END to stretch the range to the lowest rightmost cell.
6. From the Excel ribbon, select FORMULAS and click NAME MANAGER.
7. Click NEW and provide a descriptive name for the range of cells (i.e. LabourForce_import). DO NOT INCLUDE
SPACES OR SPECIAL CHARACTERS.
8. Click OK and close the Name Manager.
9. Select File > Save as…and save the file as an Excel 97-2003 Workbook (i.e. Labour_Market_CT_data.xls). DO NOT
INCLUDE SPACES OR SPECIAL CHARACTERS.
10. CLOSE EXCEL BEFORE CONTINUING.
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STEP THREE: Preparing the Census Tract boundary file
The CTuid field is formatted as ‘string’ data type. Because some CTs have been split over the years there are some cases
where a UID has a decimal (e.g. 5390102.01). In order to match the CTuid of the profile data, a new column needs to be
generated in the shapefile attribute table that is data type DOUBLE and updated with the CTuid attribute information.
1. Run ArcMap 10.x
2. Add CT shapefile (Census cartographic boundary shape files can be downloaded from Scholars GeoPortal
geo.scholarsportal.info)
3. Right click the layer name in the ‘Table Of Contents’ and click ‘Open Attribute Table’. The CT boundary file
attribute table as it appears from Statistics Canada:
4. From the Table Options dropdown menu, select Add Field.
5. In the Add Field dialogue box provide the name “CTUID_2” (using underscore,
not hyphen or space) and beside Type choose “Double”. DO NOT ENTER A
PRECISION OR SCALE. ArcGIS will automatically determine these values.
6. Click OK.
7. Right click the new field header and select “Field Calculator”. Click YES to
continue performing a calculation outside of an Edit Session.
8. From the Fields section, double-click CTUID. The calculator QUERY
window is now populated with the appropriate equation ( e.g. CTUID_2 =
[CTUID] ).
9. Click OK.
10. Resulting field calculation:
The CTUID_2 field will now match the CTuid field from CHASS table.
11. Close Attribute Table.
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STEP FOUR: Joining Census data to the boundary file
1. Click Add data and select the Named Range from the Excel workbook to add
the profile data.
2. Open both attribute tables to compare the common CTUID fields that will be used in the JOIN.
3. Join the census profile data to the boundary file using the common field “CTUID” by right-clicking the CT
boundary file from the Table of Contents and select Joins & Relates > Join
The census data is now prepared for thematic mapping.
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STEP FIVE: Creating a Choropleth Map
The following instructions are to map the percentage of population over 15 in the labour force that drive to work in the
Niagara Region.
1. Double-click the boundary file with joined census data and select the Symbology tab.
2. Select Quantities then Graduated Colors.
Most census variables are best represented as a percentage of a total population. The Value represents the
numerator while Normalization represents the denominator.
3. From the Value dropdown, select Drive_to_work.
4. From the Normalization dropdown, select Labour_Force_15_over.
5.
6.
7.
8.
9.
10.
To identify the Labels as percentages, click Label > Format Labels.
Under Category select Percentage.
Select the option “The number represents a fraction. Adjust it to show a percentage”.
Click the Numeric Options button to adjust the number of decimal places to 1.
Click OK to all dialogue boxes to return to the map view.
The final map design must be done in the Map Layout View.
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