OR/14/014 Appendix 6: Calibration report aircraft ZS-SSC

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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

14014 appendixB1.jpg
14014 appendixB2.jpg


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

14014 appendixB3.jpg
14014 appendixB4.jpg

APPENDIX C

Tabular representation of results
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

14014 appendixD1.jpg
14014 appendixD2.jpg


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