10. Additional components
Gamman can be expanded with components or "tools" for specific purposes.
The "tools" presently available are
- Background editor;
- Coordinate conversion (under separate license);
- Aux data import;
- Airborne corrections (under separate license)
- Calibration toolbox (parts under separate license)
- Borehole corrections
Gamman has extensive options for the correction of airborne data. Two options are available for processing the raw data, a 'classic' process option and an option based on the full spectrum analysis. These processing options also contain several parameters to improve the quality of the data. One can for example compensate for radiation originating from the plane, use radon calibration data and apply height corrections.
"Classic" correction of airborne data is implemented according to the guidelines of the IAEA (IAEA TECDOC- 1363). It involves correction of airborne radiometric data by using a standard elevation-dependent absorption model and an effective height based on pressure and air temperature. It also allows to include a radon background and plane background for subtraction from the measured data.
"FSA-based" correction of airborne data is an entirely different approach to airborne corrections. The model is based on using elevation dependent full spectrum analysis. That is, GAMMAN contains a library of calibration spectra for each elevation between 0.5 and 160m elevation; both for 4x4x16 NaI and CsI systems/packs. For each elevation, a set of standard spectra was created that incorporates the effects of (energy-dependent) radiation absorption in air. It also includes a calibration or standard spectrum for Radon (Rn) in air.
The algorithm is as follows:
Estimate the radon contribution. This is done by fitting K, U, Th and Rn spectra to each spectrum as a function of elevation. Though originating from merely the same radiating nuclide (Bismuth), the Rn and U spectra are strongly different, especially at the low-energy sides of the spectra. The reason for this being the difference in absorption suffered by the Rn radiation (in air) and the U radiation (from the soil). The full spectrum algorithm will separate the Rn signal from the U signal because of this difference.
Use the Rn activity to estimate for each nuclide the background, and sum with the cosmic background (based on a cosmic spectrum scaled to the counts in the cosmic channel) and a plane background.
Substract background from each spectrum and fit with K, U and Th spectra for the elevation under consideration.
The FSA algorithm thus includes all airborne calibrations at once; without the need of using an upward looking detector for Rn estimation.
The "classic" airborne corrections wizard can be accessed at Tools | Airborne corrections | Elevation
More information about the methodology can be found at Airborne corrections
The following pages are present in the "classic" airborne corrections wizard:
The welcome screen;
Assigning the input columns.
Setting the attenuation coefficients;
To set the plane background, baseline height (the baseline is the elevation that all nuclide concentrations are calculated to), and Temperature (T) and Pressure (P) at the calibration point for the P, T sensor used in the survey. A geometric correction factor can be used to scale all nuclide concentrations.
The "Full Spectrum Analysis-based" airborne corrections wizard can be accessed at Tools | Airborne corrections | Airborne FSA
More information about the methodology can be found at Airborne corrections
The following pages are present in the "FSA-based" airborne corrections wizard:
Page 1: welcome page
Page 2: settings for airborne processing.
In Elevation corrections, the columns containing elevation, temperature and pressure data can be assigned. The box "treat offscale elevation as" allows to choose what to do with spectra with an elevation above 160m. Checking tag offscale records will tag all records that have an elevation beyond 160m.
In Radon corrections, one can choose to incorporate Rn. A scaler field is used to increase or decrease the amount of Rn that is subtracted (micro-leveling). The # of records to integrate tells the software to sum a certain amount of spectra before Rn analysis, improving the stability of the solution of the fitting algorithm. Normally, between 15-30 seconds of data is integrated,
In Cosmic corrections and carrier background, the parameters for cosmic background can be set. When choosing to use cosmic channel scaling the channel containing the cosmic counts (i.e. counts above 3MeV) can be chosen in the box Cosmic channel. Also the number of records to integrate can be chosen to improve the stability of the solution. The knob View backgrounds opens a simple spectrum viewer showing the currently active carrier and cosmic backgrounds. and the option to subtract the carrier background can be checked.
Finally, in Fitting settings one can choose to sum a number of spectra for better fit-results and to apply a scaling factor to the concentrations found (usually 1). Selecting the box use smoothing guideliner allows to select a column that contains e.g. line numbers. If selected, averaging of data is only done for records having the same line number, avoiding averaging data flown in different lines.
The last page shows the processing of the data.
After finishing processing the complete dataset, a new data tab window will be created in the GAMMAN main screen and filled with the airborne FSA data just calculated. This tab will be named "airborne FSA". Selecting Clear output datasheet will erase any existing data in the airborne output sheet before entering the newly calculated data.
Cosmic wizard pages
The "Cosmics" airborne corrections wizard can be accessed at Tools | Airborne corrections | Cosmics
More information about the methodology can be found at Cosmic and carrier backgrounds
The following pages are present in the Cosmic and platform background estimator wizard:
This is the opening page of the cosmic wizard. It shows the summed spectrum from the selection made before opening the wizard. In the box labeled "Cosmic Data" you can either pick the column in the input dataset that contains the cosmic counts, or choose the cosmics stored in the last spectrum channel. By clicking the Determine cosmic and carrier spectrum you start the deconvolution process described before. After finishing, the other TABs contain the resulting cosmic and carrier background spectra. By pressing the Smoothen button, the cosmic spectrum can be filtered by 5 point smoothening, allowing to remove statistical noise inherent to the cosmic data. After pressing Close you will be asked to store the spectra or discard them.
The (unsmoothend) cosmic spectrum. Note the 511 keV annihilation peak!
The carrier background spectrum. The table lists the actual activity concentrations found in the carrier background.
Gamman supports three different backgrounds to be taken into account in the analysis of spectra:
1. A general background;
2. The "carrier" background;
3. The "cosmic" background.
The purpose and handling of these backgrounds deserves a bit of attention. The general background is the only background that can be used in the standard analysis part of Gamman. That is, whenever a spectrum is designated as a general background spectrum, it will be subtracted from the measured spectra before analysis. The carrier and cosmic background spectra are only used in the airborne corrections module, available as an additional component.
The background editor window (see below) provides a view on the background spectra currently active in your project. Tools | Background editor
The three TABs allow to switch between generic, carrier and cosmic backgrounds.
Gamman now also supports viewing and editing the calibration data used in a project. The relevant menu [Tools | calibration tools] has three submenu's, of which the first two are freely available. The third entry ([create calibration file]) is for now for Medusa internal use only.
Edit active calibration
Via [Tools | Calibration tools | Edit active calibration] you can open a form that displays the parameters set in the calibration data active in your project. Via [Tools | Calibration tools | Edit calibration file] the same form is opened, displaying a user-selected calibration file.
CAUTION: Changing calibration parameters may hugely affect the results of the data analysis. Be precautious, especially when changing the calibration files without making a backup first. More information about calibration files can be found at Calibration files.
TAB 1 contains the "Detector settings", most of which cannot be changed. The detector's ID, the number of MCA channels it provides, the detector type and the typical count rate are displayed. Also listed is a date that determines the end of the validity of the sensor's calibration data. This is an indicative date only, mostly about five years ahead of the actual calibration date.
The stabilization parameters set for the instrument are listed in the "Stabilization" box. At the bottom you see the "Analysis window" (the range in keV of the spectrum that is used in the full spectrum analysis). The "Allowed a1 range" is used by the stabilization algorithm to see if the stabilization found is within reasonable limits. For more on stabilization, see Stabilization. The resolution of the system is listed in the "Resolution" box. The numbers here are used by the airborne correction wizard to construct spectra for each elevation flown in your survey.
TAB two displays the spectra. By clicking a check, the spectrum will be hidden or displayed. The spectrum info block displays the scaling factor used for this spectrum, the spectrum code and the total count inside the spectrum. Remember, the spectra are defined as the response of your system to a source of 1 Bq/kg activity in a certain geometry and density.
TAB 3 displays some meta-data relevant for the calibration data.
Edit calibration file
See edit active calibration
Aux data import
Sometimes, it is handy to be able to import auxiliary data. Such data may for instance contain measurements of other sensors during the same survey in which your radiometry data was taken. This could be other geophysical data (EM, magnetometry, etc) and/or data from elevation meters, GPS, temperature and pressure, etc etc. Gamman now supports merging this auxiliary data into your raw data spreadsheet. The auxiliary data needs to be formatted as a spreadsheet; it should be time-ordered and it should contain a "key" column that can be merged with a "key" column in the raw data. Mostly this will be a column containing some timestamp (GPS time for instance).
The following describes the pages of this wizard which is available without an extra license.
Page 1 displays a welcome screen.
Page 2 allows to open and preview the file you want to import.
On page 3, you pick a column separator (most of the time, Gamman will find the separation for you). You can also pick the columns you want to have imported into your raw data.
Page 4 allows to do the actual merge of the data.
Select the column in the aux data that is used to match rows in the aux data sheet with the corresponding rows in the raw Gamman data. Normally these columns would contain time data of a clock known in both datasets. The edit box Significant digits allows to set the rounding that takes place before determining if records have matching timestamps. Unchecking Exact match will allow Gamman to match records of which the timestamp is smaller or equal to the aux timestamp. Checking will change the condition to just "equal". The "Missing data handling" box allows to select what to do if no matching record in the aux data is found for a certain row of raw data in your Gamman project. Either the data is constructed by interpolating between the two nearest rows that do contain data; or the last known value is used, or a value is inserted.
When the GPS is not positioned on top of the detector an offset can be applied to calculate the detector measurement location coordinates. In case of water-surveys columns can be selected for depth and cable length. 'Cable length offset' is the offset between the position of the GPS and the start of the cable.
The borehole corrections wizard can be accessed at Tools | Borehole corrections
The 'Borehole correction' wizard enables the calculation of reference borehole data from measured borehole data. The geometry and composition of the borehole and the position of the detector influence the measurement. When the measured data is corrected, data from different boreholes can be compared and interpreted.
The corrections are applied on processed data.
Corrections that can be performed are corrections for:
· Borehole diameter
· Casing thickness
· Probe position
· Formation Density
· Fluid density
· Fluid activity
After the welcome screen, the properties of the measured borehole can be entered in the "Borehole properties" box shown below.
Either a column in which the data is listed can be selected or a fixed value can be entered in the box after checking the fix box. Properties of the borehole fluid can be entered in the box to the right, mind the units! The input data columns are the columns in the processed data that will be used for the correction. Two boxes to the lower right allow to edit the reference borehole settings or to tag records that are out of range and will be discarded form the calculation.
The third page of the wizard, shown above, only opens when the "edit reference borehole settings" checkbox is set (see 2nd wizard page). The reference borehole is the standard borehole configuration used as a baseline for all calculations. Please note that changing the reference values will affect the correction. After processing, the columns with corrected nuclide data will be added to the Processed data data view as a set of extra columns containing the corrected K, U, Th and TC values.
The ´Scripter´ wizard can be accessed at Tools | Scripter This tool has been written to speed up or automate 'standard' Gamman analysis and processing. Only basic functionality has been included, any (airborne or other) corrections or checks cannot be performed using Scripter. Scripter facilitates two processing options, 'smart fit' and 'repeated average'. More information on the processing options can be found at Fitting schemes. Export, save project and close program options can be chosen. Data will be stored in de input data root. When the 'Ask for a filename' box is not checked the default filename is the filename of the first input file. Scripter can handle all possible input file types and performs a stabilization of the data first. When the box 'Auto-run scripter' is checked, Scripter will auto-run the above checked procedures after loading new input data. When checking Show Scripter warning in the Edit | Program settings window, a warning will pop-up at data import, reminding you that the Auto-run functionality of Scripter is enabled.
The TAB Output messages is a future expansion of Gamman and is not implemented yet in this version.