OR/14/014 Appendix 6: Calibration report aircraft ZS-SSC
| Beamish D and White J. 2014. TellusSW: airborne geophysical data and processing report . British Geological Survey Internal Report, OR/14/014. |
Calibration Report Aircraft ZS-SSC - Prepared by: CGG Airborne Survey - Date: July 2013
Aircraft ZS-SSC (Reims F406)
Equipment installed
| Radiometric Equipment Serial Numbers | |
| Description | Serial Number |
| Exploranium GR820 Console | 8253 |
| GPX 1024/256 Detector Pack A | 3022 |
| GPX 1024/256 Detector Pack B | 2651 |
Pad calibration procedure
The Pad calibrations were performed at Lanseria Airport using the CGG Airborne Survey portable pads on the 4th of July 2013. The following procedure was used:
- The Spectrometer system was allowed to stabilize on thorium for two hours prior to the calibration.
- The aircraft was positioned out of the way of any traffic for the duration of the tests.
- The 'hand sources' (Caesium, Uranium and Thorium) were stored in a lead box at 10 meters away from the aircraft when not used.
- The four pads, background pad (B-pad), Potassium pad (K-pad), Uranium pad (U-pad) and thorium pad (Th-pad) were stored at 15 meters away from the aircraft when not used.
- Each detector pack was calibrated separately.
- After the stabilization period the outputs from the pack not being calibrated were physically disconnected. The inputs from the pack not being calibrated were switched off in the GR820 console. Power however was maintained to the pack not being calibrated to ensure its stabilization. The above method ensures that only the response from the pack being calibrated is recorded.
- Standard background and thorium source tests were performed using aircraft jigs prior and post pad calibrations.
- The response from the B-pad was then recorded for a period of 10 minutes. This was repeated for the K-pad, U-pad and Th-pad. After the Thorium pad the response from the B-pad was again recorded. Following this the standard post calibration background and thorium source test was carried out.
- This procedure was then repeated for the other pack.
- The statistics for the data were then calculated and the stripping coefficients were calculated with the routines from Jens Hovgaard’s program padwin.
Pad calibration results
Refer to Appendix A for observed results.
Results of pack A/N 3022
| Stripping Constants | Constants | Std Devn |
| Alpha | 0.2432 | 0.0039 |
| Beta | 0.4311 | 0.0072 |
| Gamma | 0.7755 | 0.0111 |
| .a | 0.0586 | 0.0041 |
| .b | -.0065 | 0.0018 |
| .g | 0.0045 | 0.0019 |
Results of pack S/N 2651
| Stripping Constants | Constants | Std Devn |
| Alpha | 0.2285 | .0028 |
| Beta | 0.3945 | .0051 |
| Gamma | 0.7359 | .0085 |
| .a | 0.0487 | .0033 |
| .b | 0.0027 | .0016 |
| g | 0.0027 | .0016 |
Averages
| Stripping Constants | Constants |
| Alpha | 0.2359 |
| Beta | 0.4128 |
| Gamma | 0.7577 |
| .a | 0.0537 |
| .b | 0.0046 |
| .g | 0.0036 |
Height attenuation tests
Height attenuation tests were conducted at the Namibian Geological Survey Dynamic Calibration Range at Henties Bay Namibia on 10th July and 11th July 2013. The first attenuation calibration was rejected as it was found that there was a temperature inversion layer at approximately 130 m. For the second calibration there was no wind and the sky was clear.
The spectrometer system was run for two hours prior to the attenuation flight to allow it to stabilize. Standard pre-flight test background and thorium source checks were recorded for three minutes. The aircraft was flown low level to the attenuation site to maintain stabilization.
Each portion over land and water was flown sequentially at ground clearances of 900, 750, 680, 610, 540, 460, 390, 320, 250 and 180 feet. All crystals were checked during the flight to be sure of proper stabilization.
The observed data for each level was then background corrected by subtracting the mean of the background observed over water at that level. After this Compton stripping was performed. The co-efficients used were those determined at Lanseria airport. The altimeter was then corrected for standard temperature and pressure. For each channel a regression was performed between the mean STP altitudes and the natural logs of the background corrected, stripped data.
The results are shown in Appendix B below.
The attenuation co-efficients determined are:
- TOTC: -0.0077
- KCNT: -0.0099
- UCNT: -0.0089
- TCNT: -0.0078
5 Sensitivity calibration
The concentrations at the base point of the Geological Survey of Namibia (GSN) Dynamic Calibration Range at Henties Bay were measured to determine if there were any significant differences in concentrations as measured by the GSN and as measured for the current survey. The measurements are attached in Appendix C below. The concentration differences were less than 1 standard deviation and therefore the GSN concentrations for the DCR concentrations were used. These are for potassium, uranium and thorium 3.79 percent, 4.37 ppm, 16.7 ppm respectively.
From the equations of the lines for potassium, uranium and thorium determined by the above regressions the average response at ground level and 80 meters was determined in counts per second for potassium, uranium and thorium. The count rates for each channel at ground level and 80 meters respectively were divided by the respective average concentrations of the test range to give the sensitivity.
At ground level
- Exposure: 46.93 CPS/nG/hr
- Potassium: 192.74 CPS/pct
- Uranium: 18.11 CPS/ppm
- Thorium: 9.86 CPS/ppm
At 80 meters
- Exposure: 26.70 CPS/nG/hr
- Potassium: 87.31 CPS/pct
- Uranium: 8.89 CPS/ppm
- Thorium: 5.28 CPS/ppm
At height (H)
- Exposure: exp(-0.0077 * h) * 49.4260
- Potassium: exp(-0.0099 * h) * 192.7146
- Uranium: exp(-0.0089 * h) * 18.114
- Thorium: exp(-0.0078 * h) * 9.8568
Cosmic calibration
Cosmic calibrations were carried out on the 9th and 13th of July 2013 offshore from Swakopmund Namibia. The first calibration was rejected as it was affected by the presence of radon. The on shore wind was very light. The second calibration was carried out approximately 200 km out to sea. There were onshore winds of approximately 10 knots.
The spectrometer was allowed to stabilize for two hours prior to the calibration flight to ensure stability. The standard pre-flight calibrations background and thorium were performed and recorded. En route to the area the air in aircraft was flushed. Each altitude was flown at a constant height and for duration of 15 minutes. The following height levels were flown 13 000 ft, 12 000 ft, 11 000 ft, 10 000 ft, 9000 ft, and 8000 ft. Tests were flown from the highest to lowest altitude.
The results are as follows:
| Region Of Interest | Cosmic Stripping | Aircraft Background | R2 |
| Total Count | 0. 6602 | 190.49 | .9943 |
| Potassium | 0. 0380 | 23.99 | .9748 |
| Uranium | 0. 0267 |
9.89 |
.9952 |
| Thorium | 0. 0334 |
1.52 |
.9987 |
| Upward | 0. 0061 |
2.61 |
.9892 |
Summary
The calibration was carried out according to the procedures recommended in a 'Guide to the Technical Specifications for Airborne Gamma-Ray Surveys' by R.F GRASTY and BRS MINTY Record 1995/60.
The pre and post thorium source test results for the attenuation and cosmic calibrations are less than the recommended maximum of 3 % for annual calibrations. The goodness of fit coefficients, R squared, are all close to 1.
APPENDIX A
Pad Calibration Calculations
Pack S/N 3022
CALIBRATION OF K-U-TH ROI COUNTS FROM PAD MEASUREMENTS
Pad Concentration file = c:\padcal\Lanseria_Pad _Concentrations.txt
**************************************************************************
CalibrationPadName = TRANSPORTABLE TEST PADS (HANGER, LANSERIA)
**************************************************************************
| NumberOfPads | = | 4 |
| BackgroundPad_K | = | 0.290 (0.010) |
| BackgroundPad_U | = | 1.100 (0.020) |
| BackgroundPad_Th | = | 3.330 (0.070) |
| PotassiumPad_K | = | 5.795 (0.180) |
| PotassiumPad_U | = | 1.140 (0.030) |
| PotassiumPad_Th | = | 3.370 (0.060) |
| UraniumPad_K | = | 0.449 (0.010) |
| UraniumPad_U | = | 37.150 (0.390) |
| UraniumPad_Th | = | 4 .160 (0.090) |
| ThoriumPad_K | = | 0.316 (0.010) |
| ThoriumPad_U | = | 6.550 (0.040) |
| ThoriumPad_Th | = | 89.590 (1.420) |
NUMBERS IN PARENTHESES ARE ESTIMATED STANDARD DEVIATIONS
===========================================================
Processing Crystal Pack 1 (ID = S/N 3022)
| Background Pad line | : | L71003:1 21600.00 27780.00 |
| Potassium Pad line | : | L71006:1 47920.00 54180.00 |
| Uranium Pad line | : | L71005:1 38950.00 45040.00 |
| Thorium Pad line | : | L71004:1 30100.00 37050.00 |
| Background Pad line (2) | : | L71007:1 55930.00 61970.00 |
ROI COUNTS FOR PADS
| Potassium | Uranium | Thorium | #Samples | Time (Sec) | |
| Background pad | 98546.33 | 25616.45 | 22096.35 | 619 | 619.00 |
| Potassium pad | 208663.44 | 26577.14 | 21734.93 | 627 | 627.00 |
| Uranium pad | 140973.61 | 76681.82 | 25426.45 | 610 | 610.00 |
| Thorium pad | 152670.81 | 56608.91 | 103056.24 | 696 | 696.00 |
| Background pad(2) | 98011.64 | 25179.30 | 21631.77 | 605 | 605.00 |
STRIPPING RATIOS:
| TH into U (A23/A33) | : | Alpha = 0.2432 ( 0.0039) |
| TH into K (A13/A33) | : | Beta = 0.4311 ( 0.0072) |
| U into K (A13/A33) | : | Gamma = 0.7755 ( 0.0111) |
| U into TH (A32/A22) | : | a = 0.0586 ( 0.0041) |
| K into TH (A31/A11) | : | b = -0.0065 ( 0.0018) |
| K into U (A21/A11) | : | g = 0.0045 ( 0.0019) |
BACKGROUND COUNT RATES:
| K ROI : | 147.6763 ( 0.6136) |
| U ROI : | 37.8499 ( 0.2162) |
| TH ROI : | 31.3260 ( 0.2280) |
NUMBERS IN PARENTHESES ARE ESTIMATED STANDARD DEVIATIONS.
2013/07/05, 13:31:56 - Log Ended.
| THORIUM SOURCE TEST RESULTS | CPS | SDEV |
| TOTAL THORIUM RESPONSE: | 99.39 | 9.8 |
| BACKGROUND RESPONSE: | 40.32 | 5.5 |
| THORIUM RESPONSE: | 59.07 |
| THORIUM SOURCE TEST RESULTS | CPS | SDEV |
| TOTAL THORIUM RESPONSE: | 100.12 | 9.8 |
| BACKGROUND RESPONSE: | 39.91 | 5.5 |
| THORIUM RESPONSE: | 60.21 | |
| PRE & POST DIFFERENCE: | 1.930% |
PACK S/N 2651
CALIBRATION OF K-U-TH ROI COUNTS FROM PAD MEASUREMENTS
Pad Concentration file = c:\padcal\Lanseria_Pad _Concentrations.txt
*******************************************************************************************
CalibrationPadName = TRANSPORTABLE TEST PADS (HANGER, LANSERIA)
*******************************************************************************************
NumberOfPads = 4
| BackgroundPad_K | = | 0.290 | (0.010) |
| BackgroundPad_U | = | 1.100 | (0.020) |
| BackgroundPad_Th | = | 3.330 | (0.070) |
| PotassiumPad_K | = | 5.795 | (0.180) |
| PotassiumPad_U | = | 1.140 | (0.030) |
| PotassiumPad_Th | = | 3.370 | (0.060) |
| UraniumPad_K | = | 0.449 | (0.010) |
| UraniumPad_U | = | 37.150 | (0.390) |
| UraniumPad_Th | = |
4.160 | (0.090) |
| ThoriumPad_K | = | 0.316 | (0.010) |
| ThoriumPad_U | = | 6.550 | (0.040) |
| ThoriumPad_Th | = | 89.590 | (1.420) |
NUMBERS IN PARENTHESES ARE ESTIMATED STANDARD DEVIATIONS.
==========================================================================
Processing Crystal Pack 1 (ID = S/N 2651)
| Background Pad line | : | L72003:1 95360.00102180.00 |
| Potassium Pad line | : | L72006:1 120280.00126320.00 |
| Uranium Pad line | : | L72005:1 112430.00118470.00 |
| Thorium Pad line | : | L72004:1 104340.00110460.00 |
| Background Pad line (2) | : | L72007:1 128110.00134140.00 |
| ROI COUNTS FOR PADS |
| Potassium | Uranium | Thorium | #Samples | Time (Sec) | |
| Background pad | 117354.26 | 30142.29 | 27747.93 | 683 | 683.00 |
| Potassium pad | 243520.78 | 27366.97 | 24641.00 | 605 | 605.00 |
| Uranium pad | 165563.77 | 102664.05 | 29736.21 | 605 | 605.00 |
| Thorium pad | 162184.52 | 65484.70 | 142534.95 | 613 | 613.00 |
| Background pad(2) | 107260.35 | 27087.48 | 25348.23 | 604 | 604.00 |
A-MATRIX FROM NONLINEAR REGRESSION:
| 41.389866 (1.365360) |
| 2.547291 (0.038825) |
| 0.870513 (0.018000) |
| 0.110524 (0.064823) |
| 3.461555 (0.040665) |
| 0.504181 (0.010275) |
| -0.112955 (0.068226) |
| 0.168695 (0.011712) |
| 2.206679 (0.037153) |
INVERSE A-MATRIX:
| 0.024192 (0.000799) |
| -0.017533 (0.000646) |
| -0.005538 (0.000213) |
| -0.000964 (0.000463) |
| 0.292839 (0.003460) |
| -0.066528 (0.001333) |
| 0.001312 (0.000753) |
| -0.023284 (0.001542) |
| 0.457972 (0.007739) |
| STRIPPING RATIOS: | ||
| TH into U (A23/A33): | Alpha = | 0.2285 (0.0028) |
| TH into K (A13/A33): | Beta = | 0.3945 (0.0051) |
| U into K (A13/A33): | Gamma = | 0.7359 (0.0085) |
| U into TH (A32/A22): | a = | 0.0487 (0.0033) |
| K into TH (A31/A11): | b = | -0.0027 (0.0016) |
| K into U (A21/A11): | g = | 0.0027 ( 0.0016) |
BACKGROUND COUNT RATES:
| K ROI : | 156.8219 (0.7376) |
| U ROI : | 38.9489 (0.2302) |
| TH ROI : | 33.7547 (0.2912) |
NUMBERS IN PARENTHESES ARE ESTIMATED STANDARD DEVIATIONS.
=========================================================
Average stripping coefficients
=========================================================
| Alpha | : | 0.228479 |
| Beta | : | 0.394490 |
| Gamma | : | 0.735881 |
| a | : | 0.048734 |
| b | : | -0.002729 |
| g | : | 0.002670 |
=========================================================
2013/07/05, 14:30:08 - Log Ended.
| THORIUM SOURCE TEST RESULTS | CPS | SDEV |
| TOTAL THORIUM RESPONSE | 111.56 | 11.29 |
| BACKGROUND RESPONSE: | 47.56 | 6.62 |
| THORIUM RESPONSE: | 64 |
| THORIUM SOURCE TEST RESULTS | CPS | SDEV |
| TOTAL THORIUM RESPONSE: | 112.03 | 11.52 |
| BACKGROUND RESPONSE: | 46.82 | 7.76 |
| THORIUM RESPONSE: | 65.21 | |
| PRE & POST DIFFERENCE: | 1.891% |
APPENDIX B
Graphic representation of results
Thorium Source Test Results
Pre Calibration Results:
| Total Response Thorium | 261.3 cps (18.2) |
| Background Response | 117.2 cps (12.3) |
| Thorium Response | 144.1 cps |
Post Calibration
| Total Response Thorium | 264.94 cps (17.97) |
| Background Response | 117.2 cps (12.3) |
| Thorium Response | 143.65 cps |
Pre & Post difference: 1.03 cps, 0.72 pct
APPENDIX C
| ZS-SSC 2013-07-10 | ||||||||||
| Peg/position | Sample | Time | TOT | K% | U ppm | Th ppm | Tot counts | K counts | U counts | Th ppm |
| 1 | 5min | 10:00 | 32.3 | 3.4 | 4.3 | 18.8 | 1072 | 961 | 179 | 179 |
| 2 | 5min | 10:07 | 30.2 | 3.2 | 3.4 | 18.3 | 3803 | 893 | 158 | 173 |
| 3 | 5min | 10:13 | 32.4 | 3.6 | 4.0 | 18.5 | 4077 | 933 | 172 | 176 |
| 4 | 5min | 10:28 | 33.9 | 3.6 | 4.6 | 19.7 | 4272 | 1011 | 190 | 187 |
| 6 | 5min | 10:34 | 30.9 | 3.6 | 3.7 | 15.9 | 4895 | 978 | 153 | 151 |
| 7 | 5min | 10:40 | 32.3 | 3.6 | 4.0 | 18.4 | 4070 | 1006 | 172 | 175 |
| 8 | 5min | 10:46 | 30.4 | 3.6 | 3.9 | 15.6 | 3836 | 968 | 156 | 149 |
| 9 | 5min | 10:52 | 32.0 | 3.4 | 4.0 | 19.1 | 4072 | 956 | 174 | 180 |
| 10 | 5min | 10:58 | 31.1 | 3.5 | 4.3 | 16.2 | 3919 | 958 | 164 | 154 |
| 11 | 5min | 11.04 | 30.3 | 3.4 | 3.7 | 16.1 | 3820 | 942 | 154 | 153 |
| 12 | 5min | 11:10 | 29.4 | 3.6 | 3.5 | 14.4 | 3702 | 967 | 141 | 137 |
| Averages | 31.3 | 3.5 | 3.9 | 17.1 | 3944.8 | 970.6 | 162.9 | 162.2 | ||
| Std Devn | 1.3 | 0.2 | 0.4 | 1.9 | 166.0 | 233.9 | 14.9 | 18.3 | ||
| . | . | . | . | . | . | . | . | . | . | . |
| Pier 1 | 15min | 12:18 | 1.5 | 0.0 | 0.5 | 0.0 | 185 | 4 | 10 | 1 |
| Pier 2 | 15min | 12:35 | 1.4 | 0.0 | 0.2 | 0.0 | 171 | 4 | 7.5 | 1 |
| Averages | 1.45 | 0 | 0.35 | 0 | 178 | 4 | 7.5 | 1 | ||
| Pier adjustment | -2.92 | -0.4 | -0.51 | -2.12 | ||||||
| Total correction | -1.47 | -0.4 | -0.16 | -2.12 | ||||||
| . | . | . | . | . | . | . | . | |||
| Background corrected base station concentrations |
32.8 | 3.9 | 4.1 | 19.2 | ||||||
APPENDIX D
Thorium source test results
Pre calibration
Total Thorium Response: 262.57 cps (18.06)
Background Response: 118.88 cps (12.5) Thorium Response: 143.69 cps
Post Calibration
Total Thorium Response: 263.1 cps (17.54)
Background Response: 118.8 cps (11.44)
Thorium Response: 144.3 cps
Pre & Post difference: 0.61 cps, 0.43 pct