Generate Radioelement Concentrations

Use the RPS > Generate Radioelement Concentrations option (geogxnet.dll(Geosoft.GX.Radiometrics.GenerateRadioelementConcentrations;Run)*) to convert corrected count rates for Potassium (K), Thorium (Th), Uranium (U), and Total count (TC) into apparent radioelement concentrations.

To rerun the process with previous settings, select the header cell of any channel created by the process, then right-click to open the context menu. The last item in the menu represents the most recently executed process (GX). Select it to reopen the associated dialog. From there, you can rerun the process with the existing settings, adjust parameters before execution, or simply close the dialog. Learn more about Dynamic Process Links (Makers).

Generate Radioelement Concentrations dialog options

Input channel suffix	If Height Correction has been run on the current database, the suffix for the generated channels is automatically detected and preselected. If multiple sets exist, all suffixes are listed, with the most recent one selected by default. Once a suffix is chosen, the associated channels are listed below the field. Script Parameter: SPECTRO.GENERATE_RADIOELEMENT_CONCENTRATIONS_INPUT_SUFFIX
Broad Source Sensitivities If system-specific sensitivities for the survey are not available, use the default values provided as "typical sensitivities". See the Application Notes* for more details*.
Potassium (cps/%K)	Enter the sensitivity value for the Potassium (K) channel. Default: 75 Script Parameter: SPECTRO.KSENS
Uranium (cps/ppm eU)	Enter the sensitivity value for the Uranium (U) channel. Default: 7.5 Script Parameter: SPECTRO.USENS
Thorium (cps/ppm eTh)	Enter the sensitivity value for the Thorium (Th) channel. Default: 4.5 Script Parameter: SPECTRO.THSENS
Total count (µR/hr)	Enter the sensitivity value for the Total count (TC) channel. Default: 23 Script Parameter: SPECTRO.TCSENS

Output channel suffix	Specify the suffix to append to output channels. Default: `_conc`. As you type, the information string below the field updates to reflect the new output channel names. Script Parameter: SPECTRO.GENERATE_RADIOELEMENT_CONCENTRATIONS_OUTPUT_SUFFIX

Application Notes

Converting Count Rates to Apparent Radioelement Concentrations

Measured count rates depend not only on the actual concentrations of radioelements in the ground but also on the survey equipment and nominal flight height. Count rates should therefore be converted to ground concentrations of the radioelements.

Calculation Formula ^[1]

Apparent concentrations of potassium (K), uranium (U), and thorium (Th) are calculated by dividing the corrected window count rates by their respective "sensitivity" coefficients:

Where:

C = Apparent average ground concentration of the element (%K for Potassium, eU ppm for Uranium, eTh ppm for Thorium)
Ns = Average background-corrected and stripped window count rate at the nominal survey height (after applying height attenuation)
S = Sensitivity coefficient for the window

Sensitivity coefficients for each window are determined from airborne survey data collected over a calibration range. Ground concentrations of radioelements along the calibration range are measured using a well-calibrated portable spectrometer at the same time as the airborne data is acquired. This approach accounts for variations in ground radiation output caused by factors such as soil moisture and other environmental conditions.

Alternatively, sensitivity coefficients are estimated by dividing the average background-corrected and stripped window count rates (at nominal survey height) by the corresponding average ground concentrations measured along the calibration range. These coefficients are typically extracted during calibration and are often provided by the instrument manufacturer.

Reviewing Results

At each stage of radiometric processing, compare the raw, filtered, and corrected channels in the profile window to evaluate the impact of each correction step.

Complete Expressions for Apparent Radioelement Concentrations

To understand the calculation of final concentrations, the complete expressions for the Potassium and Total count channels are provided below.

*GX.NET tools are embedded in the geogxnet.dll file located in the \Geosoft\Desktop Applications\bin folder. To run this GX interactively (outside the menu), first navigate to the bin directory and provide the GX.NET tool in the required format. See the Run GX topic for more guidance.

References

[1] G. Erdi-Krausz et al. (2003), Guidelines for Radioelement Mapping Using Gamma Ray Spectrometry Data, IAEA-TECDOC-1363, International Atomic Energy Agency.
https://www-pub.iaea.org/MTCD/Publications/PDF/te_1363_web.pdf