GEOCODING SECTION 8 HOUSING VOUCHERS
The tracking of low and moderate-income housing was just one facet of the Community Outreach Partnership Centers grant awarded to the University of Nebraska at Omaha. Geocoding subsidized housing in the city of Omaha, NE was to be part of this goal. Subsidized housing is more commonly known as Section 8 Housing. The distribution of these subsidies depends upon the level of Fair Market Rents and income eligibility rules. Fair Market Rent is the upper limit on the rent that can be paid for a unit, this amount is established by the government. The amount the tenant pays is based on a fixed percentage of their income. Depending on the tenants income and family size the percentage is either 15 or 25 percent. The government pays the remaining amount directly to the landlord.
The government plays no role in choosing the rental property, though they do set up certain standards. The program provides subsidies to eligible households in existing units that are determined to be safe, decent and sanitary. The landlord does not have to accept the subsidies and can turn down tenants that want to use them. The level that the Fair Market Rent is set at also will determine the type of housing available. Newer more expensive units are easily excluded when the Fair Market Rent is set low.
PROBLEM AND PURPOSE
The problem in this project was to address match or geocode Section 8 Housing Vouchers to a street level map using the Arcview 3.0a software by ESRI. Section 8 Housing Certificates will also be done in the near future. The purpose of this project was to gain a geographic sense of where many of these vouchers are located. The maps could also be analyzed for another patterns or relationships. In the future one of the purposes of this work will be to track vouchers overtime. The maps created in this project will also be used for additional overlays to make analysis of neighborhoods throughout Omaha.
Before any addresses could be matched a street map was needed. Zooming in on a map of the United States from the ESRI Maps and Data for Street Maps a street level map of Omaha could be found. From this map a shape file was created that could be added to any view as a new theme. Within this shape file each one of the streets was broken down into segments that contained address information. This database was needed to match the addresses of the vouchers. The Map below is an example of the reference map that was used for geocoding the addresses.
Once a map that can be used as a geocoding reference theme has been created the database of vouchers was needed. The database was obtained from the Omaha Housing Authority had to be broken down into columns. Six columns were created in this database that included voucher number, address, city, state, bedroom number and voucher bedrooms. An example is given below.
|Voucher No.||Address||City||State||BD||Voucher BD|
|7502||801 So. 16th St #208||
|7504||2962 Pacific St. #3||Omaha||NE||1||1|
The only really important column for this project at this point was the address column. The addresses in this column would be matched to the street map database in the geocoding processes. Before the actual geocoding or matching of addresses could take place the database with all the voucher addresses had to be brought into the Arcview project as a table.
The next step was to create a new view. To this view the street map had to be added thus becoming the reference theme when geocoding. The geocoding index had to be made active if it was not already. Under Theme Properties the geocoding option had to be chosen. The address style could also be chosen in this dialog box. For this project the address style "US Streets" was used.
Once the geocoding index was active the geocoding process could begin. From the View menu Geocoding Addresses was selected. The dialog box that appears lets you choose from all possible reference themes. For this project there was only one reference theme, the street map of Omaha. If the address style was not selected in the Theme Properties dialog box it could also be done at this point . The only other option that had to be changed for this study was the Geocoded Theme. Once the geocoding is completed a new theme is created, the location of this new theme is chosen under the Geocoded Theme dropdown.
Once all selections and changes have been made a Batch Match could be done. When the program was finished matching all possible addresses on its own it gave the user the results. The results appear in a Re-match Addresses dialog box. The results are given in three forms, a good match, partial match and no-match. Good matches have a match score of 75 to 100 (100 being a perfect match), partial matches are address that score less than 75 and addresses that could not be located are considered no-matches. No-matches usually occur for three reasons the address is misspelled, the numbers have been transposed or the street does not exist in the reference theme.
An Interactive Re-match was done to increase the number of good matches. Changes to the geocoding preferences can be made to decrease the spelling sensitivity, minimum match score, and minimum score to be considered a candidate. At this point only the spelling sensitivity was decreased. This increased the number of possible choices for a matching address. All possible choices were displayed in the Geocoding Editor dialog box when Interactive Re-match was chosen. The closest matches could then be picked. Some of the no-matches were left unmatched because there were no strong candidates. When all possible addresses were matched a new geocoding theme was created.
The new theme that was created than could be added to the reference theme or street map of Omaha in the view. Street names were also be added to the reference theme in the view by choosing the labeling icon. Specific streets could be labeled using this tool. Because of the heavy clustering the number of labels was kept low.
The final geocoding of 1121 addresses resulted in 1075 good matches, 10 partial matches and 36 no-matches. With further work with the Omaha Housing Authority the number of no-matches could possibly be decreased. The first map, as seen below, shows a heavy concentration of Section 8 Housing Vouchers in the Northeast section of Omaha.
The zoomed view of Northeast Omaha (the area east of 72nd St and north of Dodge) gives a better view of the area with the heaviest concentration of Section 8 Housing voucher.
The following maps give zoomed in views of Southeast Omaha (east of 72nd St. and south of Dodge) and of Western Omaha respectively.
From the maps that have been produced in this project many new questions arise. First of all why is there such a heavy concentration of Section 8 Housing Vouchers east of 72nd St., especially in the northeast section of the city? Simple demographic information will probably answer this question. This is the older section of the community with a higher minority population. Census track overlays should support this view.
The greater question that the Omaha Housing Authority has to address is how to disperse the housing. Since they do not directly choose the housing they will have a difficult time dispersing the vouchers. The biggest hurtle to greater dispersion will be overcoming the stereotypes many people have of those using Section 8 Housing Vouchers.
With the use of GIS the Omaha Housing Authority will be able to track any changes that do take place. They should also be able to observe any changes in the type of housing; by monitoring housing locations they can note whether the vouchers are locating in more single family housing or other areas.
Section 8 Housing Certificates will also be done in the near future. Comparisons between these two types will then be able to be done. Census track overlays will also be added to both certificate and voucher maps. Additional overlays such as crime statistics could also be done. Strategic planning that can be done using these maps and the maps created in the future will be the greatest benefit to the neighborhoods.
Hohl, P. & Mayo, B. (1997). Arcview GIS Exercise Book. Santa Fe: OnWord
Straszheim, M. (1979). The section 8 rental assistance program: costs and policy
options. Policy Studies Journal, 8, pp. 307-323.
LIST OF FIGURES
Figure 1 .... Street map of Omaha, NE
Figure 2 .... Example table for addresses
Figure 3 .... Section 8 Vouchers in Omaha, NE
Figure 4 .... Section 8 Vouchers in northeast Omaha
Figure 5 .... Section 8 Vouchers in southeast Omaha
Figure 6 .... Section 8 Vouchers in west Omaha
Presented by Amy Schaeufele, April 30, 1998.