Establishment and Ground-Based Characterization of Natural Reference Sites for UAS Gamma Spectrometry Standardization

Abstract

Uncrewed aerial system (UAS) gamma spectrometry is a powerful tool for environmental radiation monitoring, effectively filling the gap between ground-based and classic large-scale airborne surveys. Although the technological development of UAS radiation detection systems is rapid, the lack of standardization in data processing workflows still limits their widespread application and comparability among independent surveys. This letter presents the establishment and characterization of a first-of-its-kind, nationally certified, and publicly accessible reference infrastructure for UAS radiometry, consisting of permanent natural reference sites for K, U, Th, and artificial 137Cs, designed as physical benchmarks supporting global UAS radiometry standardization. To address temporal variations, repeated ground-truth monitoring (including in situ gamma spectrometry, soil moisture tracking, and atmospheric radon assessment) was systematically integrated into the experimental design. This infrastructure will host the first group intercomparison exercise in October 2026, organized in cooperation with the International Atomic Energy Agency (IAEA).