Tutorial using the 2011 Statistics Canada boundary files and the Householder survey

Transcription

1 Tutorial using the 2011 Statistics Canada boundary files and the Householder survey In this tutorial, we ll try to determine the wards that contain the highest income groups. To do this, we will have to import the household income data from Statistics Canada s 2011 Householder survey -- it s weaknesses notwithstanding and then link that Excel file to Ottawa s Census Tract shape file, and then pull in the Wards shape file we ve used in previous tutorials. Having all these files linked and layered in ArcMap will allow us to make a heat map that uses the darkest colours to identify Ottawa s highest income areas. It s worth noting that the same can be done for 29 topics categorized in the list below: Aboriginal population Age at immigration Citizenship Class of worker Education Ethnic origin population Full-time or part-time weeks worked Generation status Household characteristics Immigrant status and period of immigration Immigrant status and selected places of birth

2 Income of households in 2010 Income of individuals in 2010 Industry Labour force status Language used most often at work Median commuting duration Mobility Mode of transportation Non-official languages spoken Occupation Occupied private dwelling characteristics Place of work status Recent immigrants by selected place of birth Religion Shelter costs Time leaving for work Visible minority population Work activity Although this list may seem impressive, the quality of the information pales in comparision to the last 2006 census. Back then, I was able to use a more precise map that drilled deeper (areas representing 400- to 700 persons) using what s called dissemination areas. These areas allow journalists to map areas neighborhoods, really -- by characteristics such as topics listed above. Traditionally, journalists have attempted to establish possible connections between income level and phenomena such as crime. Despite the fact that correlation doesn t necessarily mean causation, it s still worth examining possible

3 connections as starting points for story ideas, which is one of the reasons why journalists find census data interesting and important, and a key reason why we re doing this tutorial that uses imperfect data as its source. In 2006, Statistics Canada used the mandatory long-form census to obtain information such as income level. When the Conservatives made the controversial decision to replace the long-form census with a voluntary Householder Survey, information such as income was no longer available at the dissemination area, or neighborhood, level. Instead, that data was collected according to census tracts, much broader geographic units containing 2,500 to 8,000 persons. To make matters worse, because responding to the Householder Survey is voluntary, the results are not as accurate a representation of the income levels. It s important to understand this context because the key to working with any data set is understanding the strengths and weaknesses of the numbers. The Carleton library also has information on the Census and Householder Survey that it s worth reviewing. So despite the weaknesses of the 2011 census, it s useful to learn how to use get Census and Householder Survey information into ArcMap to see patterns that may, at the very

4 least, arm us with interesting questions for policy makers, academics and politicians. So let s get started with the tutorial. 1) As a reference point for exercises that go beyond this tutorial, download the zip folder containing the Ontario census tracts, which include Ottawa. This file contains data from all the categories itemized in the introduction. 2) For specific use in this tutorial, download the household income data and import the data from the worksheet called OttawaHouseholdIncome. NOTE: I ve added a decimal place and added two zeros to the numbers in the Geo_Code column, and then changed the data type to text to match the Census Tract Unique Identifier or CTUID. As well, I left the dollar values formatted as numbers rather than currency. ArcMap uses these identifiers Geo_Code and CTUID -- to place the census tract boundaries and their contents on the map. Below, is screen grab of the attribute table once the two files are joined in ArcMap. After joining the files, I reformatted the values in the Total column as currency by right-clicking on the column label to produce a drop-down menu, and

5 then selected the Properties option. 3) ArcMap has imported the numbers in the CTUID field as text, which is why we had to reformat the Geo_Code numbers to text, but not before adding a decimal place and two zeros. 4) Let s import the Ottawa census tract file. (The file is also located on Statistics Canada website where you would select the radio box to the left of English under the Language heading, and ArcGIS under the Format heading, and then check off the radio box to the right of Census Tracts under the Digital Boundary File heading, select the Continue Tab and download the gct_+000a11a_zip file. Once you pull this file into ArcMap, you d have select only the Ottawa tracts and export that selection as a new shape file that only contains Ottawa tracts, and not Gatineau.)

6 5) So at this point, you should have two files to import into ArcMap: the household income Excel file and the Ottawa Census Tract boundary file. 6) Open ArcMap 7) Import shape file. 8) Import the household income Excel file and open the attribute table.

7 9) 10) Right click on the icon for the Ottawa shape file 11) 12) Select the Join option to connect the values in the Ottawa Census Tract shape file s CTUID field with the

8 values in the Excel file s Geo_Code field. 13) Select the OK tab.

9 14) Open the shape file s attribute table to see that it has been joined to the Excel file.

10 15) To format the numbers as currency, right click to Total column in the attribute table

11 16) Click the icon to the right of the Numeric tab 17) Select Currency, OK and then Apply 18)

12 19) To find out where all the people with money live, we ll create a heat map. 20) Now we have to save this layer as a shape file, which will also replace the Null values with zeros. 21) Allow ArcMap to add the new layer to the table of contents and get rid of the previous one. 22) Your new shape file s attribute table should look like this when you sort the values in ascending order. 23) Right click on the Ottawa shape file icon that now contains the household income data and select Properties and then Symbology in the Layer Properties dialog box. 24) Select the Quantities option in the Show box to the left, and then Graduated colours.

13 25) You ll see a drop-down box to the right of the Values option under the fields category. Choose the Total column which contains the household incomes. 26) ArcMap defaults to five categories or classes. Let s choose a few more household income groupings. 27) Choose eight 28) Your Layer Properties box should look like this.

14 29) If you re fine with the colour, hit the Apply and Okay tabs. 30) The hotspots are difficult to see in this colour ramp. Perhaps it might be easier if we gave the two highest categories the colour black.

15 31) To do this, click on the second-highest income grouping in the menu to obtain a Symbol Selector box. 32) Double-click on the red tab to the right of the Fill Colour option and choose the darkest colour from the palette.

16 33) 34) Select the OK tab and repeat the same process for the highest income-level grouping, this time using grey.

17 35) 36) Now we have a better idea of the hotspots for the two highest household income groups. 37) But there are no labels, at least not ones that would make sense to the people reading your story. Without labels, it s difficult to identify the hotspots by boundaries. 38) To solve this problem, we can import the ward shape file. 39)

18 40) Your colour may be different. We want to ward colour to recede to the background, and only show the names. 41) To do so, right click on the Wards shape file icon in the table of contents 42) Click on the tab under Symbol and select the No Colour option from the colour palette, and then select OK. 43) Select the Labels tab from the menu at the top and check the box to the left of the Label features in this layer option. 44) And then under the Text String section, chose WARD_EN (the column in the ward file that contains the

19 names) from the drop-down menu to the left of the Label Field option. 45) If your screen looks like my screen shot, hit the Apply and OK buttons. 46)

20 47) The names are difficult to see. Perhaps they d be more visible with a lighter colour. 48) Let s return to the Labels section of our Layer Properties box, and select a different colour. As you can see in the screenshot below, I ve chosen yellow. 49) Once you re happy with the selection return to the map, zoom in to some of the hotspots. 50) Before adding a base map, let s project the map. 51) Right click on the Layers tab right under the Table of Contents title. 52) Click on Properties 53) Select the Coordinate System tab

21 54) Under "Select a Coordinate System." Expand Predefined 55) Expand Projected Coordinate systems 56) Expand National Grids 57) Expand Canada 58) Select NAD 1983 CSRS MTM 9 59) 60) Click Apply, and then OK 61) Select YES if you get pop ups.

22 62) To help situate these household income-level areas, let s import a basemap. To do so, go to File on your menu at the top, Add Data, and Add Basemap. 63) 64) Select OpenStreetMap.

23 65) 66) From here, we can either save the result, which contains all the layers, as a PDF, something we learned in the second ArcMap tutorial, or save one of the layers, in this case the joined Census Tract and Household income a KML file that we can pull into Fusion Tables. There are a few ways to do this. 67) You could use ArcMap s Geoprocessing function, the ArcToolbox, Conversion Tools, To KML, Layer to KML.

24 68) 69) ArcMap actually saves the file in a KMZ format, which is actually a zipped KML file. To extract that file, you would simply change the KMZ extension to Zip, and then extract the KML file. 70) Fusion Tables also has a converter that changes shape files into KML. 71) We ll use Qgis, an open-sourced mapping program that many people use as an alternative to ArcMap. An added bonus is that Qgis works on Macs. So it s a good

25 idea to have a working knowledge of Qgis. The program easily converts a shape file to KML. 72) You download Qgis here. 73) If you have two screens, simply drag and drop the census file into Qgis 74) 75) If you only have one screen, right click on the shapefile icon in the Layers section on the left hand side, and select the Save vector layer as option from the drop-down menu. Be sure to select the Keyhole Markup Language [KML] format, browse to save the file in the appropriate folder, and select the OK tab.

26 76) 77) Now you ll be able to upload the KML file to Fusion Tables and, based on what we learned in the previous tutorial, create a heat map according to whatever specifications you choose.