Map-Your-Own-Data Definitions

Visible Layers:

Cities/Towns

A mix of both incorporated places (legal entities) and census designated places or CDPs (statistical entities). An incorporated place is established to provide governmental functions for a concentration of people. Places always nest within a state, but may extend across county and county subdivision boundaries. An incorporated place usually is a city, town, village, or borough, but can have other legal descriptions. CDPs are delineated to provide data for settled concentrations of population that are identifiable by name, but are not legally incorporated under the laws of the state in which they are located. Click on city/town name to highlight the boundary. Reference Source: U.S. Census, 2020.

County Commission Districts

For more information, see http://www.accg.org/. The districts were established in 2014, and were obtained from the Association of County Commissioners of Georgia (ACCG). Further processing was performed by the Office of Health Indicators for Planning (OHIP) of the Georgia Department of Public Health. History and role: In 1868 the state began creating the position of county commissioner to administer the general operations of the county. Today every county has a commissioner; many have a board of commissioners (BOC). As part of general county operations, the BOC must finance county programs. A BOC has the power to adopt ordinances, resolutions, or regulations relating to county property, county affairs, and the operation of local government (http://www.georgiaencyclopedia.org/nge/Article.jsp?id=h-589 ).

GA House Districts

Electoral districts from which State Representatives are elected. The Georgia Constitution requires not less than 180 Representatives apportioned by population from representative districts. Layer Source: https://www.legis.ga.gov/, Adopted 2023 – Effective for 2024 Elections.

GA Senate Districts

Electoral districts from which State Senators are elected. The Georgia Constitution limits the number to not more than 56 single member districts. Senate districts are apportioned based on population. Layer Source: https://www.legis.ga.gov/, Adopted 2023 – Effective for 2024 Elections.

Hospitals

Hospitals are the non-Federal acute-care inpatient medical facilities in Georgia. Click on the symbol to get the name. Reference Source: Georgia Hospital Association, 2021.

Interstates

Interstates are the freeways that are part of the Interstate Highway System in Georgia. The Interstate Highway System connects major cities within the United States. Click on the line to get the Interstate number. Layer Source: Esri, March 1, 2012.

Major Roads

Major roads are a combination of both federal and state highways connecting cities and towns. Click on the line to get the route number. Layer Source: Esri, March 1, 2012.

Perinatal Regions

The Perinatal Regions were established by the Department of Public Health in cooperation with the six teaching hospitals located in Atlanta, Albany, Augusta, Columbus, Macon and Savannah. The Regions reflect the hospital referral patterns for high risk pregnant women and newborns. Each of the six hospitals has a Regional Perinatal Center which has contracts with the state and receives funding to care for high risk pregnant women and infants as well as to train staff from other hospitals in perinatal care especially for high risk patients. Reference Source: Georgia Department of Public Health, March 2005.

ZIP Code

Established by the U.S. Postal Service for distribution of mail. Zip codes do not generally respect political boundaries or census areas such as tracts. Zip codes usually do not have clearly identifiable boundaries, often serve a continually changing area, are changed periodically to meet postal requirements, and do not cover all land area in the U.S. Layer Source: Esri, June 1, 2020.

ZIP Code Tabulation Area (ZCTA)

Zip Code Tabulation Areas (ZCTA’s) are a geographic entity made by the Census to approximate Zip Codes. USPS ZIP Codes identify the individual post office or metropolitan area delivery station associated with mailing addresses, and are not in fact areal features but a collection of mail delivery routes. ZCTA’s were created as areal features for use with statistics, change every 10 years, and have the same five-digit names as the Zip Codes they represent.

Base Layers:

Base layers are background information to provide contextual references for local-level maps. They are especially suited for tract-level maps and give real-world reference to maps you create in OASIS. There are three toggle-able (on/off) base layers:

Demographic Clusters

Demographic Clusters refer to the socioeconomic status classifications created by OHIP, and are at the census block-group level. More information here: https://oasis.state.ga.us/gis/demographiccluster/DemoClusters2011.htm.

Aerial Photography

Aerial Photography refers to ESRI's World Imagery.

Socioeconomic Vulnerability

Socioeconomic Vulnerability refers to the socioeconomic status domain/subset of the CDC’s Social Vulnerability Index (SVI), and is at the census tract level. Socioeconomic vulnerability ranks tracts within the state on 4 factors: below poverty, unemployed, income, and no high school diploma. Percentile ranking values range from 0 to 1, with higher values indicating greater vulnerability/lower socioeconomic status. Quartiles were used to create class breaks. For more information see https://www.atsdr.cdc.gov/placeandhealth/svi/index.html. For data dictionary click here.

Street Map

Street Map refers to ESRI's World Street Map with street-level data for North America.

Data Classification Methods:

Natural Breaks (Jenks)

This method minimizes within-class variance and maximizes between-class variance in an iterative series of calculations. This method seeks to partition data into classes based on natural groups in the data distribution. Natural breaks occur in the histogram at the low points of valleys. Breaks are assigned in the order of the size of the valleys, with the largest valley being assigned the first natural break.

George F. Jenks is considered a pioneer in GIS educational programs. Through an award from the Fund for Advancement of Science, Jenks identified four key objectives for cartographic training. Robert McMaster and Susanna McMaster; A History of Twentieth-Century American Academic Cartography

Source: Brewer and Pickle. Evaluation of Methods for Classifying Epidemiological Data on Choropleth Maps in a Series. Annals of the Association of American Geographers, 92(4), 2002, pp. 662-681.

Quantiles

• Data values for each enumeration unit (e.g. county or census tract) are ranked from lowest to highest.
• The total number of values is divided by the number of classes specified by the user to determine how many values each class will contain. The object is to obtain a roughly equal number of data values within each class. For example, if you have 100 census tracts and the tract data values are to be classed into 5 classes, each class will have 20 values (100/5 = 20).
• In some cases, an equal number of values will not be placed into each class. For instance, if there are an odd number of enumeration units some classes will have a larger number of data values than others. If data values for the 159 counties of Georgia are divided into 4 classes, then some classes might have 39 data values while others have 40. In addition, identical data values are maintained within the same classes. Continuing the Georgia county example, if 45 of the lowest data values are 0, then the lowest class will have 45 data values all with a value of 0.

The quantiles method of classification is provided because:

• Quantiles classification is one of the simplest methods of classification and is easy to understand and interpret.
• Classes are usually centered on the median, a measure of central tendency, and "they group enumeration units above and below the median into classes with equal frequencies regardless of their values." This makes maps easier to compare with one another.
• Many health-related measures are distributed normally (i.e. a large number of values falling near the middle of the data range with a smaller number of values on the low and high ends of the data range) making quantiles classification a logical classification method.

Source: Brewer and Pickle. Evaluation of Methods for Classifying Epidemiological Data on Choropleth Maps in a Series. Annals of the Association of American Geographers, 92(4), 2002, pp. 662-681.

Map Tools

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V1.4 (8/8/2024)