Tutorial 9: Upward-Detector a1, a2 Calibration

Database Setup

This tool calculates the a1 and a2 coefficients required by the upward-detector method for estimating atmospheric radon. The tool requires background-corrected window count rates, which can be acquired in two ways:

    1. A series of Offshore-Onshore Lines. The lines are split into offshore and onshore parts, with the offshore parts being used to correct the onshore parts for total background to yield a background-corrected window data, and
    2. A survey flown over land can be used to estimate a ground spectrum using an Along-Line Differencing technique. Successive groups of window count rates along the line are differenced (where the radioactivity gradient is large enough) to effectively yield background-corrected window data. 

Use either Intrepid or Oasis Montaj to set up all the input database fields required by the tool. You will see which fields are required at Step 3 below. Of course, for an Intrepid database, the line number, flight number and fiducial fields must also always be present in the database – with prescribed names as indicated in the "Preparing The Database" section.

Note that this tool requires the upward-detector uranium window field. So prior to running this tool, the upward-looking spectra must be energy-calibrated, and the upward U window sampled. That is, steps 2 and 3 in "Tutorial 1: Processing Airborne Data" – but for the upward-looking spectra

Processing Steps – Offshore-Onshore Lines

    1. Open a database from the Main Window – File|Open. For the demonstration dataset select "demo_data\airborne_spectrometry\upward_detector_a1a2_offshore-onshore\UP_DETECTOR_A1A2_OFFSHORE_ONSHORE..DIR" (or the Oasis Montaj equivalent).
    2. Launch the tool – Calibration|Upward-Detector a1, a2.
    3. Set the database aliases and tool parameters – File|Set Aliases and Parameters. Click the Load From File button and select the "aliases_and_params_radonA1A2_offshore_onshore.pc" control file from the working directory. For an explanation of the aliases and parameters click the Help button. Click Save And Return.
    4. Select the calibration lines from the database. Do this by selecting each of the Select buttons next to the Cal Line Select textBoxes. Click the file icon next to the top-most Cal Line Select textBox and select line 100010. Repeat for lines 10020, 100030, 100040, 100050, and 100060.


Tool Tip:  You can use the following shortcut to select lines: The top Cal Line Select button has the focus (after setting aliases and parameters), so pressing Done on the keyboard brings up the Line Select window. Select the line with the mouse, then press Done on the keyboard to exit the window. Now the second Line Select button will have the focus, so repeat for each line.


    1. Select the background lines from the database. Do this by selecting each of the Select buttons next to the Bgd Line Select textBoxes. Click the file icon next to the top-most Bgd Line Select textBox and select line 90010. Repeat for lines 90020, 90030, 90040, 90050, and 90060. You can use the same Tool Tip shortcut described above after manually giving the top Bgd Line Select button the focus using the mouse. 
    2. Make sure the Offshore-Onshore checkBox is checked and click the Calculate button to do the background corrections and calculate a1 and a2. 
    3. View the log file – File|View User Log File to see the full results.
    4. Save the results – File|Save Results to save the calibration constants to a file in a form suitable for cutting/pasting into a control file for airborne processing. 

Processing Steps – Along-Line_Differencing

    1. Open a database from the Main Window – File|Open. For the demonstration dataset select "demo_data\airborne_spectrometry\upward_detector_a1a2_differences\UP_DETECTOR_A1A2_DIFF..DIR" (or the Oasis Montaj equivalent).
    2. Launch the tool – Calibration|Upward-Detector a1, a2.
    3. Set the database aliases and tool parameters – File|Set Aliases and Parameters. Click the Load From File button and select the "aliases_and_params_radonA1A2_diff.pc" control file from the working directory. For an explanation of the aliases and parameters click the Help button. Click Done.
    4. Click the Run button to estimate the a1 and a2 coefficients. 
    5. View the log file – File|View User Log File to see the full results.
    6. Save the results – File|Save Results to save the calibration constants to a file in a form suitable for cutting/pasting into a control file for airborne processing.