Calibration constants for the Geodata International, Inc., and Texas Instruments, Inc.: High sensitivity systems used for the ERDA aerial gamma-ray surveys

The radiometric data from the ERDA aerial gamma-ray surveys have been presented in the form of count rates proportional to the apparent, average surface concentrations of potassium (K), equivalent uranium (eU), and equivalent thorium (eTh). Data from a U.S. Geological Survey calibrated, truck-mounted gamma-ray spectrometer have been used to estimate calibration constants that can be used to convert the count rate data to absolute concentration units--percent K, parts per million (ppm) eU, and ppm eTh. Calibration constants for the gamma-ray systems of Geodata International, Inc. and of Texas Instruments, Inc. as they were configured prior to September 1976 are presented.