Defining service catchment areas in low-resource settings

► Defining an accurate, representative service catch- ment area is important for computing population de- nominators for disease mapping and efficient public planning, including health, education and social care. ► The growth in population settlement modelling tech- niques and provision of geocoded service databases has fuelled an increase in local and regional service access mapping to examine coverage and equity in much of sub-Saharan African countries. ► However, metrics of service access and catchments are often implemented based on convenience, disregarding the implications on accuracy of the catch- ment population, complexities of service use and the likely implications for public service planning. ► Lack of high spatial resolution geolocated data on residential locations of the service users has led to the use of rudimentary, inexact approaches to com- plex processes that define service catchment areas and should be used with caution. ► The improved collection of residential addresses of service users and service providers has increased the ability to develop new innovative models of ser- vice catchment. ► Improved data availability and data sharing must be accompanied by better models of service use. ► In this commentary, we revisit the issue by considering common approaches, key issues and best practices in defining a reliable service catchment area. ► We hope this will lead to further granular studies to populate and compare methods to improve the definition of service catchment areas in sub-Saharan Africa, ultimately improving efficiencies and equity in service use and more reliable interpretations of routine service use data.