Alabama Geography and Demographics

Introduction

This project explores geographic point and area layers that are useful for healthcare analysis, along with demographic data corresponding to the layers. The geographic information is displayed in an interactive map while the demographic information is displayed in interactive tables. All of the data, geographic and demographic, can be downloaded.

The interactive tables can be sorted on any field by clicking on the appropriate column header, and the data can be filtered by searching for text in the search bar. The buttons at the top of the table allow the table data to be copied to the clipboard, printed, or saved in various standard formats.

Layers

The term area layer refers to a collection of contiguous, non-overlapping geographical regions. The term point layer refers to a collection of locations that are idealized as geographical points, with each point characterized by a latitude and longitude. lThe primary layers used for our healthcare projects are as follows:

• Communities. Alabama has 580 communities recognized by the US Census Bureau, each classified as either a city, a town, or a place. The communities, as defined by their administrative boundaries, form an area layer, although one that does not partition the state. The communities, as defined by their center points, form a point layer.
• Counties. Alabama's 67 counties form one of the basic area layers in a governmental and administrative sense. This layer partitions the state.
• Core-Based Statistical Areas. A Core-Based Statistical Area (CBSA) is a collection of contiguous counties anchored by an urban center. Alabama has 13 CBSAs that collectively contain 30 counties. The remaining 37 counties can be considered completely rural, and so the 13 CBSAs together with the collection of rural counties forms another area layer that partitions the state.
• Primary Care Service Areas. Alabama has 79 Primary Care Service Areas (PCSAs) defined by the UAB Huntsville Office of Family Health, Education, and Research. Each PCSA is centerd by a community with a significant collection of medical resources (and usually a general-admission hospital). The PCSA itself is defined as the region of the state that is closer to this centroid than any other, as measured by drive times and the Alabama road system. The PCSA area layer also partitions the state, but is more rational from a healthcare standpoint than administrative and legislative layers.
• ZIP Codes. Technically, a ZIP code refers to a collection of mail addresses, but ZIP codes are also frequently converted into geographical areas, known as ZIP Code Tabulation Areas (ZCTAs). Alabama has 650 five-digit ZIP codes and 19 three-digit ZIP codes; each corresponds to an area layer that partitions the state. In addition, the five-digit ZIP codes define a point layer, with each point corresponding to a special address with that ZIP code.
• HRSA Service Areas. These are primary care service areas defined by Human Resources Service Administration, and are compose of contiguous ZCTAs. This area layer does not quite partition the state, since there are small regions that are not a part of a HRSA service area.
• Alabama House Districts. There are 105 districts in the Alabama House of Representatives. These form an area layer that partitions the state.
• Alabama Senate Districts. There are 35 districts in the Alabama Senate. These form an area layer that partitions the state.
• US House Districts. Alabama has seven districts in the US House of Representatives. These form an area layer that partitions the state.
• Census Tracts. Alabama has 1179 Census Tracts defined by the US Census Bureau. This area layer partitions the state, and is particularly important because the census tract is the basic geographical unit for which demographic data are available.

Fields

Most of the area layers have the same type of geographic and demographic fields (or variables) that are displayed in the tables.

• Area. The area of the region in square miles.
• Tracts. The number of census tracts in the region, although a census tract may not respect the boundary of the region. That is, a region may contain only a portion of a census tract.
• Population. The total population, the population of males, and the population of females in the region.
• Units. The number of housing units in the region.
• Households. The number of households in the region.
• FIPS. The Federal Information Processing Standard, a set of codes used, among other purposes, for geographic regions.
• GNIS. The Geographic Name Information System, developed by the US Geographical Survey, is a standard code for geographical places.

User Interface

Our data are displayed in the form of interactive maps and tables. The maps generally have point or area layers that can be added or removed with the layer control on the map. The user can zoom in and out of a map and move about in the usual way. Zooming in reveals additional features such as small towns and then streets and roads. A click on the home button returns the map to its origional location and scale. The zoom-to-area button allows the user to zoom to a selected rectangular area of the map. Clicking on an object in a layer shows summary data for that object.

The interactive tables can be sorted by any field, by clicking on the header for that field. The buttons at the top allow the table data to be copied to the clipboard, in tab-separated text format, printed, or downloaded in various formats (tab-separated text, Excel, or PDF). With the search bar, the table can be filtered according to a text string.

In the interactive tables you can click on a row to select an object and see the object highlighted in the map. You can select as many rows as you wish. Click on a selected row again to de-select and remove the highlight in the map.