The Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (SJTREM) has published a study defining a mission-based method to determine a HEMS units actual service area. 

Geographical service areas are used as descriptive system indicators in Emergency Medical Service (EMS) related studies and reporting templates. The actual service area may differ significantly from administrative areas; this may lead to inaccuracy in determining indicator values, such as population or mission density, thus making it biased when comparing results between different areas and organizations.

The aim of this study was to introduce a unequivocal, repeatable and easily adaptable method to determine the actual service area of a helicopter emergency medical service (HEMS) unit for statistical, quality measurement and research purposes using widely available geographical information (GIS) and statistical analysis tools.

View the full study