Radiometrics processing
Contents
1. number of samples to gather statistics and aid the signal de noising process This is most beneficial for Uranium estimates You may be able to further enhance results by combining local spectra to boost the signal noise statistics There is an option to do this in INTREPID Overview NASVD smoothing 1 Run Multi Channel Processing and input the spectrum to be smoothed 2 Select only NASVD Smoothing and Channels to be Saved 3 Accept the default 8 principal components for the NASVD process unless you have a strong reason for doing otherwise 4 Save the spectrum as an output file If you save the windowed data you can grid it and check the results of the NASVD processing 2012 Intrepid Geophysics 4 Back gt Library Help Top INTREPID User Manual Radiometrics processing C07b 13 Library Help Top lt 4 Back gt Overview MNF smoothing 1 In the Project Manager from the Radiometrics menu launch the Maximum Noise Fraction tool and open the dataset 2 Specify the spectrum to be smoothed 3 Specify whether you want INTREPID to perform the integration or stacking of the individual spectra on a line by line or a flight by flight basis before PC analysis 4 Specify the name of the output smoothed spectrum 5 Select the Advanced tab 6 Specify the number of principal components for the MNF process Accept the defaults for First and Last Good Channel What is in the radiometrics sample data cookboo2. INTREPID Gridding tool grid the uppm_1_lev field As before use the Visualisation tool to examine the grid Further exploration If you have completed the main exercise and have some spare time try adjusting the parameters following parameters and examine any differences in the results The following table suggests some adjustments you can make Parameter Change Implication and Effects C1 Decrease Estimates that the contribution from Radon to the Radon window is larger so removes a higher proportion of counts C2 Decrease Estimates that there is a smaller Compton scattering contribution from Uranium in the Radon window Integration time bunch size Decrease Uses shorter line segments to calculate the Radon contribution If you make it too small you degrade the data Library Help Top See Minty 1997 for a description of the derivation of C1 C2 C3 and C4 You can also save the Radon peak as a dataset field by selecting it in the Channels to be saved dialog box Gridding and inspecting this field may give you a clearer picture of where Radon is affecting the survey data 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing CO7b 12 Library Help Top 4 Back gt View individual spectra If you are processing 256 channel data it can sometimes be useful to view the raw spectra We shall do this using the supplied data 1 Launch the Multi C
3. see Gridding T22a Solution datasets and optional steps For each stage of this worked example we have provided solution datasets or fields that you can use as input for the next stage if you do not wish to carry out this stage of the example Location of sample data for Cookbooks Where install_path is the path of your INTREPID installation the project directory for the Cookbooks sample data is install_path sample_data cookbooks For example if INTREPID is installed in C Program Files Intrepid Intrepid4 5 then you can find the sample data at C Program Files Intrepid Intrepid4 5 sample_data cookbooks For information about installing or reinstalling the sample data see Sample data for the INTREPID Cookbooks in Using INTREPID Cookbooks R19 For a description of INTREPID datasets see Introduction to the INTREPID database G20 For more detail see INTREPID database file and data structures R05 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 2 Library Help Top lt 4 Back gt Location of dataset files In this worked example we assume that the example datasets reside in directory install_path sample_data cookbooks radiometrics buffalo If the sample data is not present If the sample data is not present as described above and we have not supplied you with a CD ROM you need to download it from our website Go to http www intrepid geophysics com then
4. INTREPID User Manual Radiometrics processing C07b 1 Library Help Top 4 Back gt Radiometrics processing C07b Top Overview This cookbook demonstrates the stages in processing radiometric data In the exercises you 1 Ensure that your copy of INTREPID is registered and install the Cookbook data from the INTREPID install CDROM 2 View the grid datasets provided showing the original data and the results of the radiometrics processing 3 Use the Multi Channel Processing tool to compute NASVD spectral smoothing on the raw 256 spectra data 4 Use the Multi Channel Processing tool to perform remaining full spectra corrections and extract standard K U Th and Total Count windows 5 Use the Standard3 tool to compute Compton stripping height corrections and radio element conversions on K U Th and Total Count fields 6 Grid the processed radiometric fields 7 Use the Uranium levelling tool to remove any residual radon levelling problems from the Uranium field 8 Miuicrolevel etc Preliminary notes Library Help Top We assume that you understand How to use a suitable visualisation tool for examining grids For this worked example we recommend the INTREPID Flight Path Editor the INTREPID Visualisation tool or ERMapper For instructions on using both of the INTREPID tools see Flight Path Editor T19 If necessary for your choice of optional steps how to use the INTREPID Gridding tool For instructions
5. cify output fields for windowed data Run the task and view its progress Library Help Top Channels to be saved Under Field Selector heading use the Select buttons to display dialog boxes for selecting fields and specify output windowed data fields Radiometrics processing C07b 7 4 Back gt If you do not want to overwrite the existing fields add _1 to the field names totnasvd256_1 knasvd256_1 unasvd256_1 thnasvd256_1 Choose OK Channels to be saved Channel to Save Save Channel Parameters selected as a group Low Mev limit High Mev limit Save Field Selector Dataset Field Spectral data 0 0000000 3 0000 x TotalCount Window 0 4100 2 8100 Select No Alias Present Select totnasvd256 1 3700 1 6600 2 4100 0 5800 Potassium Window Uranium Window Thorium Window LowUranium Window 1 5700 Select knasvd256 aa E Select unasvd256 Select thnasvd256 r Select No Alias Present OK Cancel Choose OK then choose OK to dismiss the Processing Options dialog box Run the task as specified Watch the progress of the task in the graphs that INTREPID displays Choose Apply in the main window INTREPID displays six spectra profiles corresponding to the stages of the process as shown in the diagram below It displays the data for the line just processed refreshing the display for each line Stage 4 The airc
6. counts in the 0 609 MeV Radon window to the Bi214 U window to estimate the amount of Radon contamination The process requires a 256 channel pure Radon spectrum in the calibration file The constants C1 and C2 and the integration period control the extent of radon removal from the data C3 and C4 are normally set to zero Increasing C1 estimates that the contribution from Radon to the Radon window is larger so removes a higher proportion of counts Decreasing C2 estimates that there is a smaller Compton scattering contribution from Uranium in the Radon window The Compton stripping ratios alpha beta and gamma and terrain clearance parameters are used to remove K U Th contributions from the raw Radon count rate NOTE This process does NOT perform Compton stripping even though the stripping ratios are required Initially we use the default values for C1 and C2 Set the values for C3 and C4 to zero Initially we leave the integration period at 400 samples Set the stripping ratios Alpha Beta Gamma to 0 2395 0 3940 0 6443 This process also requires the survey terrain clearance Make sure the reference terrain clearance is set to 80m which was the nominal survey height Click on the Select Terrain Clearance button and from the dialog box select effective_ht_ml and choose OK Choose OK to dismiss the Radon Background Removal dialog box 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Spe
7. ctrometric processing C07 Library Help Top 2012 Intrepid Geophysics 4 Back gt
8. e noise cleaned spectrum as a new output file in the dataset 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 5 Library Help Top Run the remainder of the multi channel processing corrections View the dataset parameters Examine other parameters lt 4 Back gt Clear the Save check box corresponding to the Totent K U Th windows At this stage there is no need to extract the standard windows Press OK to exit the dialog box and OK to exit the Processing Options dialog box Now select Apply in the main window of the tool After a pause the processing begins and graphs appear showing the raw spectrum the NASVD smoothed spectrum and the 8 principal components for each processed line When all lines are processed a message box appears Choose OK to return to the main tool From the File menu Choose Quit to exit from the tool Run the remainder of the multi channel processing corrections As before launch the Multi Channel Processing tool From the File menu choose Load Line Dataset Choose Select Line Dataset and open buffalo_sub DIR Choose Select Calibration Data and select cosmic_radon_jwf asc from the list of calibration files This file contains the calibration spectra for aircraft cosmic and radon background signatures Select Spectrum Field this time set the Spectrum Field to spectrum_nasvd this is the NASVD smoothed spectrum Leave the sample in
9. ecords the Live time as a data field Choose the Use Measured Live Time option and choose Select Live Time From the dialog box with the list of fields select 1time and choose OK Energy Calibration The Energy Calibration process needs to know where in the spectrum the main K U Th peaks are located The Energy Calibration parameters supply this information in terms of the spectrum channels Normally you would derive these values from the spectrum data by using the View spectrum function on the main tool interface However for this example we just use the default values which should suffice Energy calibration by line is recommended Cosmic and Aircraft Background Removal With 256 channel processing the background corrections can be done as full spectrum corrections Single window coefficients are replaced by spectra which have a unique value for each channel in the spectrum These spectra are stored in the calibration file Consequently the background corrections can be performed more accurately than is possible using windowed data In the Cosmic Aircraft Background Removal dialog box check Remove Cosmic Background and click the corresponding button From the dialog box select cosmic and choose OK Check the Remove Aircraft Background check box and choose OK Radon Background Removal INTREPID uses the spectral ratioing method described by Minty 1992 to remove radon from the 256 channel spectra data It examines the ratio of
10. fficients with 54 48 6 21 3 14 Choose OK Apply the process Choose Apply in the main window to run the selected processes 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 11 Library Help Top lt 4 Back gt 7 Grid the fields Using the INTREPID Gridding tool grid the totcps_1 kpcent_1 uppm 1 thppm_1 fields Compare the grids to the previous grids Uranium levelling Try adjusting In this section you learn how to use the Potassium and Thorium fields to remove any residual radon artifacts in the Uranium data The method is based on the assumption that for background corrected data the U flight line means are a linear function of the K and Th flight line means 1 Dataset Selection parameters Launch the Uranium Levelling tool From the File menu choose Load Input data gt Open Input Potassium Select buffalo_sub DIR and then select the kpcent_1 field in the Select Input Potassium Field dialog box In the Select Input Uranium Field dialog box select uppm_1 In the Select Input Thorium Field dialog box select thppm_1 From the File menu choose Save Output Data In the Select Output Uranum Field dialog box type uppm_1_ulev Choose OK 2 Apply the process To apply the process press Apply in the main window A message box appears containing a log summary of the mean line values for the input fields and the corrections applied to the output field Using the
11. for errors If the energy calibration process stage 3 is going wrong the red area surrounding a peak appears markedly asymmetric perhaps excluding the peak itself This is the most common cause of failure If the aircraft or cosmic background processes stages 4 and 5 are going wrong the profile drops significantly Under normal circumstances the change in these stages should be imperceptible in the profile display If the Radon background process stage 6 is going wrong the Uranium peak channel 149 disappears The main change you see when the process is going correctly is fluctuations in the Radon lower Uranium window channel 51 when compared with the stage 5 profile If an error appears note the line number at which it occurs You can then view the log file for the line and review the parameters for the process Tip Log file The Multi Channel Processing tool can generate a comprehensive log as it proceeds This log contains vital information for checking the results troubleshooting and obtaining technical support The Windows version of INTREPID appends this log to its log file nt lt user gt 1log Return to the main tool interface but leave the Multi Channel Processing tool open 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 9 Library Help Top 4 Back gt Grid the corrected data fields Using the INTREPID Gridding tool grid the totnasvd256_1 knasvd256_1
12. ge of processing the count rate representing each K U Th window is significantly affected by counts from the adjacent windows The data is also contaminated by background radiation contributions from the aircraft cosmic rays and the presence of Radon gas escaping from the ground You can see the effect of Radon most clearly in the U grid The count rate is also affected by the ground clearance of the detector as well as the volume of the detector In order to reduce the data to a more meaningful state such that we can draw valid conclusions as well as make sensible comparisons with other surveys we need to carry out a series of corrections to the raw data Central to applying these corrections are a series of calibrations which are carried out separately before during and after the survey The calibration data must be prepared and the results of these calibrations are stored in a special file which INTREPID uses during the processing of the 256 channel data Accurate radiometric data processing is impossible without properly collected calibration data In INTREPID the preparation of calibration data is done using the Calibration spectra processing tool prior to any radiometric data processing In INTREPID radiometric data processing is done using the following tools e Multichannel Processing for 256 channel data corrections Standard3 Corrections for corrections to extracted window data Uranium Leveling for removal of residual Rad
13. hannel Processing Tool 2 From the File menu choose Load Line Dataset 3 Ihn the Please select the line dataset dialog box Choose Select Line Dataset and open buffalo_sub DIR Leave the calibration file as the default Choose Select Spectrum Field and select spect rum Choose OK 4 Inthe main window choose View INTREPID displays the Choose line number for testing dialog box 5 Select any line from the list and choose OK INTREPID sums all the individual spectra for the current line and displays them as a single spectrum plot Choose Next or Previous to navigate to different lines Determine channel positions of IAEA peaks The Energy Calibration process requires high and low channel bounds for the main photo peaks These must be determined accurately from the data otherwise the process may fail to find the main peaks In the Multi Channel Processing tool point to the spectrum plot Values for x and y appear on the graph The x value is the spectrometer channel number corresponding to the cursor position When you are finished choose Cancel From the File menu choose Quit Performing NASVD or MNF smoothing You may wish to perform NASVD or MNF smoothing before the multi channel corrections On a large dataset the spectral smoothing could take several hours Both NASVD and MNF processes are straightforward so we have omitted detailed steps If you process by flight instead of by line it ensures that INTREPID uses a higher
14. her parameters the same Choose OK to dismiss the Radon Background Removal dialog box Choose OK to dismiss the Processing Options dialog box Choose Apply in the main window Grid the corrected data fields Library Help Top Using the INTREPID Gridding tool grid the totnasvd256_1 knasvd256_1 unasvd256_1 thnasvd256_1 fields Compare the grids to the previous grids 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 10 Library Help Top 4 Back gt The standard 3 processing tool Dataset selection parameters Library Help Top In this section you learn how to apply the following corrections to the standard gamma ray spectrometer fields K U Th and Total Count 1 6 Stripping correction for Compton scattering Normalise measurements to a standard distance above the ground Height attenuation Conversion of count rates in the air to element concentrations on the ground Dataset Selection parameters Launch the Standard 3 gamma ray adjustment tool From the File menu choose Load Line Dataset The Select Line dataset dialog box appears Choose Select Line Dataset and open buffalo_sub DIR Next choose Select TotalCount Field and select the field totnasvd256_1 from the list of field names Similarly for Potassium Uranium Thorium select the fields knasvd256_1 unasvd256_1 thnasvd256_1 fields If you have previously completed the 256 multichanne
15. k The radiometrics cookbook contains the following datasets The radiometrics line dataset buffalo_sub DIR This radiometrics dataset is a subset of a larger dataset that was originally flown over the 1 100 000 Buffalo map sheet in the Eastern Highlands of Victoria Australia The test dataset is a helicopter survey with specifications e 200 metre line spacing 80 metre terrain clearance GR820 spectrometer with 16 8 litres of crystal detector 1 second sample rate 40 metres second aircraft speed Real time Differential GPS navigation The buffalo_sub DIR dataset contains the following fields Field Dimension Description fid Scalar Fiducial flight Scalar Flight number line Scalar Line number linetype Scalar Line type easting Scalar East West location northing Scalar North South location radalt Scalar Terrain clearance temp Scalar Temperature effective _ht_ml Scalar Terrain clearance corrected for temperature and pressure also called STP height dtmfinal_ml Scalar Digital terrain model microlevelled spectrum 256 band Raw 256 channel spectra recorded by the spectrometer in real time Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing CO7b 14 Library Help Top 4 Back gt Field Dimension Description spectrum_nasvd 256 band 256 channel spectra af
16. l helicopter equipped with an Exploranium GR820 256 channel spectrometer These instruments utilise real time automatic gain stabilisation based on tracking of the Thorium peak to control the tendency of the spectrometer to drift The gamma ray detector had a total crystal volume of 16 8 litres The sampling interval for the radiometric data was 1 0 second approx 45 metres sample spacing The survey line spacing was 200 metres and the flight lines were flown in an E W direction The mean survey flying height was 80 metres 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 3 Library Help Top lt 4 Back gt View the grid datasets provided View the View the three supplied grids kroi uroi troi of the window data supplied For supplied grids ease of viewing the three grids simultaneously we suggest that you use the INTREPID Flight Path Editor the INTREPID Visualisation tool or ERMapper These grids show the standard radiometric windows extracted from the International Atomic Energy Agency IAEA defined regions of interest K U Th in the raw 256 channel spectrum data They represent the data at a completely unprocessed stage Using the visualisation tool the Load Ternary Grid option is a good way of viewing the 3 bands of radiometric data Chosose K as the red colour Th as the green colour and U as the blue colour This create a standard RGB 3 channel display At this early sta
17. l processing exercise fields for Cosmic Livetime and Clearance should already be assigned If not make sure that you assign them Leave the Sample interval at 1 0 seconds From the File menu choose Save Output Fields Specify output data fields totcps_1 kpcent_1 uppm_1 thppm_1 if you do not want to overwrite the existing fields Run Compton stripping From the Processes menu choose Compton Stripping For the Value at ground replace the default Alpha Beta Gamma stripping ratios with 0 2395 0 3940 0 6443 Leave the reverse ratios and height attenuation factors as defaults Choose OK Height attenuation From the Processes menu choose Height Attenuation Replace the default Total Count Potassium Uranium Thorium coefficients with 0 006958 0 008911 0 006510 0 006878 Choose OK Terrain clearance limits From the Processes menu choose Terrain Clearance Limits These are the valid height ranges and the nominal survey altitude for the height correction Enter a minimum value of 10m maximum value of 110m and a nominal value of 80m Choose OK Conversion to Ground Concentrations From the Processes menu choose Conversion to Ground Concentrations These sensitivity coefficients are used to convert counts per second to ground concentrations For this exercise we convert K U Th but leave Total Count as counts per second Leave the value for Total Count as the default of 1 0 Replace the Potassium Uranium Thorium coe
18. o Launch the Multi Channel Processing tool From the File menu choose Load Line Dataset Choose Select Line Dataset and open buffalo_sub DIR Select Calibration Data leave the calibration file as dfa_default asc The NASVD process does not require any special calibration data Select Spectrum Field ensure that the Spectrum Field is set to spect rum this is the raw spectrum Leave the sample interval as 1 0 seconds Choose OK From the Processes menu select Corrections The Processing Options dialog box appears Selected check boxes which are checked indicate that those options included in the processing Check the Selected check box corresponding to NASVD smoothing and choose NASVD smoothing The dialog box allows you to specify the number of principal components which the NASVD process uses to reconstruct the spectra For this exercise we save the default of 8 components Choose OK The following further options are available e Boost Signal Noise ratio by Adjacent Spectra addition e Save Spectralal Components and Amplitudes The Selected check box for Channels to be saved is already checked Click on the coresponding button The Channels to be saved dialog box appears From Field Selector choose the top Select button corresponding to Spectral data The Select Spectrum Field dialog box appears At Enter New Field Name type spectrum_nasvd and choose OK Check the Save box to the left of the Select button This saves th
19. on problems e Maximum Noise Fraction for an alternative spectral smoothing method to NASVD Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 4 Library Help Top 4 Back gt The Multichannel Processing Tool Run NASVD spectral smoothing Library Help Top In this section you learn how to apply the following corrections to 256 channel radiometric data Noise Adjusted Singular Value Decomposition NASVD spectral smoothing Livetime corrections Aircraft background and cosmic radiation corrections Radon corrections Extraction of IAEA standard Total Count and K U Th photopeaks from the 256 channel spectra data All steps can be run in one single operation However in practise the NASVD smoothing takes much longer to run than the other steps so with a large dataset it is more practical to run the Multi Channel Processing tool in two stages NASVD spectral noise reduction smoothing The remainder of the multi channel processing and corrections In this tutorial we do the processing in two stages 1 Run NASVD spectral smoothing This is the first step in the radiometrics data processing sequence In this example we shall use the NASVD method to smooth the raw 256 channel spectra data Note that both NASVD and MNF smoothing methods support line or flight based processing and also spectra stacking a method which boosts the Signal Noise rati
20. raft background removed spectrum Stage 5 The cosmic background removed spectrum The display includes the Stage 6 The radon background removed spectrum The display includes the The raw spectrum The normalised spectrum corrected for livetime dead time The display includes IAEA standard windows IAEA standard windows the IAEA standard windows Stage 1 Stage 2 Stage 3 The energy calibrated spectrum stretched or contracted so that the peaks corresponding to the IAEA standard windows have standard channel numbers From this stage INTREPID displays the IAEA standard windows K U Th 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Radiometrics processing C07b 8 Library Help Top Library Help Top lt 4 Back gt Here is an illustration of the profile windows as they appear on the screen Aircraft Background Removed Spectrum Cosmic Background Removed Spectrum Radon Removed Spectrum Line 142011 Line 142011 Line 142011 1 00 0 00 128 00 256 00 0 00 128 00 256 00 Channel No Channel No Raw Spectrum Nomeksed Spootrum Energy Calibrated Spectrum Line 142011 Line 142011 1 00 Lire 142011 256 00 0 00 128 00 256 00 Channel No 128 00 Channel No Tip Watching
21. ter NASVD smoothing deleted ltime Scalar Live time recorded by the spectrometer in real time cosmic Scalar Cosmic count total counts gt 3 MeV recorded by the spectrometer in real time totroi Scalar Raw Total Count 0 4 3 0MeV recorded by the spectrometer in real time and summed kroi Scalar Raw data recorded by the spectrometer in real time and summed for K window uroi Scalar Raw data recorded by the spectrometer in real time and summed for U window troi Scalar Raw data recorded by the spectrometer in real time and summed for Th window totcps Scalar Final processed Total Count data kpcent Scalar Final processed Potassium data uppm Scalar Final processed Uranium data thppm Scalar Final processed Thorium data totnasvd256 Scalar Total Count data after NASVD correction multi channel processing and then rewindowing knasvd256 Scalar Potassium data after NASVD correction multi channel processing and then rewindowing unasvd256 Scalar Uranium data after NASVD correction multi channel processing and then rewindowing thnasvd256 Scalar Thorium data after NASVD correction multi channel processing and then rewindowing Spectra Calibration file A spectra calibration file cosmic_radon_jwf asc contains the aircraft background cosmic background and Radon calibration spectra for the data This file exists in the directory install_path config calibration_spectra References See References in Multi channel gamma ray spe
22. terval as 1 0 seconds Choose OK View the dataset parameters Please select the line dataset Please select the line dataset Dataset Selection Parameters Select Line Dataset CAlntrepid int37c226 cookbook radiometrics cookrad_ DIR Select Calibration Data CAlntrepid int37c226 config calibration_spectra cosmic_radon_jwf asc Select Spectrum Field lspectrum_nasvd Sample Interval seconds 1 0000 OK Cancel Examine the parameters for the other corrections From the Processes menu choose Select Corrections INTREPID displasy the Processing Options dialog box Check boxes that are checked indicate that those options are included in the processing Check all processes except for NASVD smoothing which has already been done Processing Options Processing Options Processing Options Option Selected NASVD smoothing Livetime Deadtime Normalisation aa 7 Energy Calibration al Cosmic Aircraft Background Removal a Radon Background Removal Channels to be saved al OK Cancel 2012 Intrepid Geophysics Library Help Top 4 Back gt INTREPID User Manual Library Help Top Library Help Top Radiometrics processing C07b 6 4 Back gt We now go through the parameters for each step in detail To view the parameters for each process click on the appropriate process button Livetime Deadtime Normalisation In this survey the spectrometer was a GR820 which r
23. to Downloads Log in creating an account if necessary and go to Data The dataset is available in that page Download it and unzip it into the folder described above System requirements To process the Radiometrics worked example you need about 45 Mb hard disk space If you wish to save your own new NASVD or MNF smoothed spectrum you need an additional 25 Mb Steps to follow Registering your copy of INTREPID Ensure that your INTREPID installation is licensed You must have at least an evaluation licence to run the radiometrics worked examples Contact Intrepid Geophysics or one of our agents if you require an evaluation license Copy the radiometrics sample data from the supplied CDROM Introduction Library Help Top If we supplied you with a CD ROM copy the radiometrics sample data to install_path sample_data cookbooks radiometrics buffalo For more information see Preliminary notes The data includes e The survey line dataset buffalo_sub DIR with raw data and supplied solution fields Solution grid datasets The data you process in this cookbook was acquired over the 1 100 000 Buffalo map sheet as part of the Victorian Initiative for Minerals and Petroleum VIMP The data custodians are Geoscience Victoria Department of Primary Industries Melbourne Australia The data is freely available through the Geoscience Australia GADDS Geophysical Archive Data Delivery System This data was acquired by a Bel
24. unasvd256_1 thnasvd256_1 fields Using the visualisation tool view the grids you have created The Load Ternary Grid option is a good way of viewing the 3 bands of radiometric data Select K as the red colour Th as the green colour and U as the blue colour This creates a standard RGB 3 channel display What can you say about the Uranium grid Has all of the Radon contamination been removed It is clear from this example that not all of the radon has been removed from the Uranium signal For most surveys flown over relatively flat terrain Radon contamination is generally fairly constant down a flight line however this dataset was collected over a series of hills and valleys resulting in an uneven radon distribution down the flight lines You can see from examining the RGB display that the Radon has collected in localised pockets in the valleys under the flight lines In the next example we re apply all the corrections except for NASVD using different parameters for the Radon correction Return to the main menu of the tool and from Processes select Corrections Radon Background Removal An integration period for the radon removal must be used because of the low count rate in the Radon window Decreasing the integration time results in more localised radon removal but the downside is that a smaller integration time also introduces more noise into the corrected data This time change the integration time to 50 seconds Leave all ot
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