A baseline terrestrial air kerma map of Queensland, Australia was developed using geochemical data from a major drainage catchment ultra-low density sampling program (overbank sediment).

A generic terrestrial air kerma background value is proposed for Queensland, Australia.

Validation of three catchments comparing in-situ measurements, and radiometric & non-radiometric laboratory methods confirm suitability of the methodology.

Large land areas may be mapped using the catchment sampling method at significantly lower cost as opposed to resource intense comprehensive sampling and measurement programs.