GPS and Geographic Information Systems (GIS)

Geographic Information Systems (GIS) GPS Clusters

Geographic location affects peoples' health, nutrition, and access to health care services. The DHS Program can now analyze the impact of location using DHS data and geographic information systems (GIS). These spatial analyses improve our understanding of how location affects health status, leading to more effective interventions.

The DHS Program routinely collects geographic information in all surveyed countries. Using GIS, researchers can link DHS data with routine health data, health facility locations, local infrastructure such as roads and rivers, and environmental conditions. Linked DHS and geographic data are now being used to improve planning for family planning interventions, to assess the correlation of malaria prevalence and anemia in children in West Africa, and to analyze the effects of environment on early childhood mortality.

In addition to the resources above, here is a list of additional resources geospatial prepared by The DHS Program.

GPS Data Collection

In most recent DHS surveys, the groupings of households that participated in the survey, known as clusters, are geo referenced.  These survey cluster coordinates are collected in the field using GPS receivers, usually during the survey sample listing process. In general, the GPS readings for most clusters are accurate to less than 15 meters.  Additional GPS data collection information is available in the GPS data collection manual.

In order to ensure that respondent confidentiality is maintained, we randomly displace the GPS latitude/longitude positions for all surveys, including those that do not have HIV testing.   The displacement is randomly carried out so that:

  • Urban clusters contain a minimum of 0 and a maximum of 2 kilometers of error.
  • Rural clusters contain a minimum of 0 and a maximum of 5 kilometers of positional error with a further 1% of the rural clusters displaced a minimum of 0 and a maximum of 10 kilometers.

The displacement is restricted so that the points stay within the country and within the DHS survey region. In surveys released since 2009 the displacement is restricted to the country's second administrative level where possible.

For clusters without GPS readings, other means are used to determine the coordinates.  Coordinates may be extracted from a paper map or a gazetteer of settlement names.  For some surveys, cluster coordinates are extracted from preexisting census data provided by the country's census agency/ministry.  Regardless of the source, all collected coordinates are always checked for accuracy before they are displaced and then released to the public. The source of the coordinates (GPS, map, gazetteer) is reported in the geographic data file that is released to the public.  The DHS GPS data format provides detailed information about what information is available in each publicly-released geographic data file.

Geographic Data Analysis

When using the GPS data for analysis users should beware of common mistakes:

  • All GPS locations of household clusters are displaced (see the section above for details), but SPA facility data is not displaced.
  • GPS locations are an estimated center of a cluster, not at the exact household locations.  Cluster sizes can vary greatly.
  • Measuring direct distance from a GPS location to some other site (Facility, school, etc) is not correct since this does not account for the displacement of the GPS locations. Using categories of distances or buffers is a better approach.

Spatial analysis publications provide examples of geographic analysis using GPS data from The DHS Program.

For clusters without GPS readings, other means are used to determine the coordinates.  Coordinates may be extracted from a paper map or a gazetteer of settlement names.  For some surveys, cluster coordinates are extracted from preexisting census data provided by the country's census agency/ministry.  Regardless of the source, all collected coordinates are always checked for accuracy before they are displaced and then released to the public. The source of the coordinates (GPS, map, gazetteer) is reported in the geographic data file that is released to the public.  The DHS GPS data format provides detailed information about what information is available in each publicly-released geographic data file.

GIS Training

The geospatial team at The DHS Program offers an annual Health Data Mapping Workshop to cohorts of public health professionals working in DHS countries. Before the COVID-19 pandemic, these workshops were offered in-person. GIS specialists from The DHS Program would travel to different countries and invite professionals from the surrounding region to attend the week-long program. However, due to the risks of traveling during the COVID-19 pandemic, the workshop was converted into an online format and is now offered on the DHS Learning Hub.

In this workshop, participants learn how to:

  1. Create maps for making decisions and planning programs,
  2. Present and explain maps for policymaking and decision-making, and
  3. Develop a plan for future application and transference of knowledge to colleagues.