Massachusetts Institute of Technology Department of Urban Studies and Planning 11.520: A Workshop on Geographic Information Systems 11.188: Urban Planning and Social Science Laboratory Lab Exercise 5: Working with 2000 Census Data Overview In this exercise you will extract raw data from Census STF3 files to create a thematic map indicating the percentage of workers in block groups in Middlesex County who drive alone to their jobs. You may find the notes from the "Making Sense of the Census" lecture* and Accessing Online Census Data in ArcView* a useful reference. Your goal is to create a table that contains the percentage of workers who drive alone to work (by car, truck, or van) for each block group in Middlesex county. Note that unlike the simple example shown in class, to complete this task you must normalize* the data. You may want to look at the section consider a different example* for information on the appropriate "universe" variable. Necessary Resources : View the "Making Sense of the Census" lecture notes* and the "Accessing Online Census Data in ArcView"* lecture notes for background information on this topic. Summary File 3 : Technical Documentation (.pdf)* : local version* | census web page version* - Chapter 3: Subject Locator This index is designed to quickly identify the STF3 tables you may need. Each table variable is listed alphabetically. - Identification Section : Table (Matrix) Section Use this section to find the data dictionary number for the STF3 table that you are interested in. - Chapter 2 : How to Use This File One of the most important parts of this chapter is the explanation of how to extract the correct geographic summary level. * Refer back to the Lab section.2000 Census Variable Locator* - Once you find the census variables you are interested you can use this file to locate the 2000 Census data file that holds your variable. Hints The find tool may come in helpful when trying to find a variable in the 2000 Census Technical Documentation. Search for keywords like "Means of Transportation to Work" and "Persons 16 years and over". Getting Started Create a Shapefile of Block Groups in the Boston Region Launch ArcView and go to File>Extensions to add the MIT Geodata Search Tool. This tool allows you to search for data in MIT's spatial database. This spatial database holds boundary and statistical data from all over the world. The MIT Geodata Search Tool allows you to locate data and add it to your active ArcView view. Once the file in opened in ArcView you can perform simply analysis or download the data file to your computer. After the MIT Geodata Search Tool is added in the ArcView extensions dialog, an icon and menu item will appear allowing you to access the tool. Use this tool to find Massachusetts Block Groups for 2000 census. (Hint: Search on all the layers in Massachusetts) A results dialog will appear. * Refer back to the Lab section.Press the View metadata button to look additional information on the file. Once you find the file, highlight it and press the Add selected layer to view button to add the layer to your view. Exit the MIT Geodata Search Tool. Use Theme > Table or icon to open up the attribute table for this theme. What column are you going to use to link this coverage to external block group census data? In order to work with a smaller file create a new Shapefile that represents the 2000 Massachusetts Block Groups that fall within major Boston area counties (Essex, Middlesex, Worcester, Suffolk, Plymouth, Norfolk, Bristol, Branstable). To create a new Shapefile that represents the 2000 Block Groups in our area of interest (Boston area counties), we need to select the appropriate block groups and convert them to a new Shapefile. To select the 2000 Block Groups, in your area of interest, you will use ArcView's Select By Theme... tool. This tool will select features in one theme that intersect with selected features in another. To use the Select By Theme... tool you need to have a layer that represents the 2000 Massachusetts Block Groups and another layer that represents the U.S. Counties. You will select the Massachusetts counties that define your area of interest and than use that selection to find the block groups that fall within those counties. To do this follow the steps below: STEP 1: Use the MIT Geodata Search Tool to find the U.S. Counties (Generalized) layer.(Hint: Try using Title as you search type.) Add the layer to the same view as the Massachusetts Block Groups 2000 layer. STEP 2: Highlight the Select tool and use it to select Essex, Middlesex, Worcester, Suffolk, Plymouth, Norfolk, Bristol, and Branstable counties from the U.S. Counties (Generalized) layer. When selected these counties should appear yellow.STEP 3: With the counties selected you are ready to use the Select By Themes... tool. This tool works on the currently active theme, so you will need to make the Massachusetts Block Groups 2000 theme is active. Go to the Theme menu and select Select By Theme... When the dialog appears. Choose to select features from your active theme (Massachusetts Block Groups 2000) that Intersect with the selected features of the U.S. Counties (Generalized) file (sde_data.us_ma_e25blkgrp_2000). Press the New Set button and wait while ArcView processes you request. STEP 4: All the Block Groups that intersect with Essex, Middlesex, Worcester, Suffolk, Plymouth, Norfolk, Bristol, and Branstable should now be highlighted. You are ready to create a new file based on these selected features using ArcView's Convert to Shapefile tool. (Hint: Convert to Shapefile can be found in the Theme menu.) Call this new theme b_blkgrp.shp and save it to your working directory. STEP 5: In your view, remove the layers you added through the MIT Geodata Search Tool. We no longer need these file and their size could effect processing speed. Form this point you will only need to use the b_blkgrp.shp file. Working with Census Data : Finding The Variables To complete the lab, you must create one or more files with the subset of the data you need. Follow these steps to create the files: STEP 1: In order to facilitate your use of the 2000 Census STF3 files for Massachusetts, they have been loaded into the Athena locker census. The census files we've saved are located in /mit/uscensus/stf3a2000, but you still have to determine which STF files and data fields you will need for: • Workers who drive alone to work (See Means of Transportation to Work in