Airborne radiometric data are provided here as part of the data release "Airborne magnetic and radiometric survey, Munsungun Region, northern Maine, 2021." This website includes the processed aeroradiometric digital flight line data (gamma spectrometry for K, U and Th) provided in an ascii .csv file and geoTIFF images showing a ternary image of relative K, U and Th and individual K, U, and Th values. Radiometric spectra are provided in ascii and binary formats within the contractor package on the parent page. The contractor report is also available on the parent page. Data for this survey were collected and processed by Sander Geophysics under contract with the USGS as part of the Earth Mapping Resources Initiative (Earth MRI). Using a fixed wing aircraft with a magnetometer mounted in a tail stinger and a fully calibrated gamma ray spectrometer, data were collected along northwest-southeast flight lines spaced 250 meters (m) apart with northeast-southwest tie lines flown every 2500 m. The target terrain clearance was 100 m, with higher clearance over areas with rugged topography and population centers due to safety considerations. A total of 43,271-line kilometers (km) of data were collected. Processing details are provided in the contractor report.