Mapping the Seattle Region with ArcGIS and the Washington Geospatial Data Archive

1. Mapping the Seattle Region with ArcGIS and the Washington Geospatial Data Archive Instructor: Jonathan Glick July 17 2008Center for Social Science Computation & Research 601 Condon Hall University of Washington http://julius.csscr.washington.edu

2. The Uses of WAGDA • Many research projects at the UW make use of locally collected data • Many of these projects can be enhanced by some form of mapping • UW library has conveniently organized spatial data from local governments and the US Census in the Washington State Geospatial Data Archive (http://wagda.lib.washington.edu) • Most WAGDA data requires a valid UW netid and cannot be used for any commercial purpose.

3. Geographic Areas in WAGDA • Seattle City Data • If all data is within the city limits of Seattle, highly detailed data • County level data • WAGDA also has extensive data for King County, and varying amounts of data for other WA counties as well. • Multi-county data • When mapping areas larger than a single county, you way want to consider other data sources. The Puget Sound Regional Council (PSRC) has Census boundary files for the entire Puget sound region • Tina Tian, CSSCR data archivist can help with other data sources

4. Example: playgrounds in Seattle • Let’s say we are studying playgrounds in the city • We may already have a list of playgrounds in the study but no map or census tract information. • Goals: • Reference maps of the playground locations • Find demographics of neighborhoods around them.

5. In Windows, create a work folder for yourself (mapping projects can use up a lot of disk space!) In a web browser, open WAGDA’s City of Seattle page Download the data for playareas and Census 2000 tracts to your work folder. In Windows, Unzip all of the files by right-clicking the folders and selecting “Extract here.” Download City of Seattle data from WAGDA

6. Open ArcMap from the ArcGIS folder in the Start menu. Choose an empty map. ArcMap displays information by layering one spatial file on top of another On the left side of the screen is the ‘table of contents’ – this is where you add and delete data. The right side of the screen displays the data. Toolbars are movable and include navigation tools similar to those found in web mapping Introducing ArcMap

7. Add data by clicking the button on the toolbar: Map your work folder using the button: Add the playareas, Census tracts Drag the layers in the table of contents and zoom in to get the layering shown Use the identify tool by clicking on the map Note the coordinates at the bottom of the screen, which are Washington State Plane. Creating a simple reference map

8. Open the attribute table for tracts by right-clicking it’s name. Note that there is a field called “water” designating the portion of tracts over water. From the Selection menu, choose Select by Attributes. Run a query to select all areas in “tract00” that are not water, as shown. Right click on the Tracts layer and choose “Selection> Create layer from selected features.” Use the check-box to turn off the old tracts layer and rearrange the other layers. Save when done Improving the look of the map

9. Open the layer properties of Tracts (double-click or right-click) and select the labels tab Label the tracts using “tractlab” as shown at right Change the layer names by writing over them in table of contents Select a new symbol for play areas by using the symbology tab Similarly, pick a color for the tracts layer Save the map when happy with the look! Improving the look, continued

10. Switch to the layout view using the button at bottom left Apply a map template with the ‘switch layout’ button From the General templates choose “LetterPortrait” Modify map elements for clarity The Map may now be printed or exported (file menu) or copied to clipboard (edit menu) Preparing for print or export

11. Notes on saving and moving projects • ArcMap mapping projects are made up of many separate data files • The “map” file (.mxd) contains pathways to all the other data files • It is useful to store relative paths when moving data that is contained within one folder • Select ‘File>Document Properties’ and click ‘Data Source Options’ • Use full paths if data will remain in one place (e.g. network drive), relative otherwise • Select the “source” tab at the bottom-left of the table of contents to view each layer’s data source

12. Options for adding Census data • Open the attribute table for the Census tracts. There is no demographic data but ‘Tract00’ is a tract number that can be matched to data from other sources. • Options for adding demographic data • From the Census website you can download specific tables for all tracts with Seattle • For those familiar with Microsoft Access, WAGDA offers Census geodatabases • Download popular tables from Puget Sound Regional Council • Geolytics Census CD’s . Available from Tina Tian, data archivist of CSSCR • Of these options the Geolytics CD is probably the most simple to use but can only be used at CSSCR. All data sources will require some modification in order to join to the tracts table. See me (Jon) at CSSCR for further help

13. Tips on joining new tables to Census tract layers • Use Excel to create/modify a table • Create a column that exactly matches the tract name field in the ArcMap data layer • Create a single header row with short variable names • Save the sheet as a DBF file (easiest in Excel 2003) • Follow the instructions on joining at: http://julius.csscr.washington.edu/pdf/arcgis.pdf • Joins sometimes fail because a text field cannot be matched with a numeric field (even when both appear to be numbers). You can convert a text field to a number as follows: • Add a new field to the attribute table using the “Options” menu at the bottom of the table. Make the field a long integer • “Calculate values” for the new field by right clicking on the column name. • Set the new field equal to the existing text field. It will automatically convert to numeric.