OR/14/014 Part 3: Data processing - Revision history

Dbk at 08:52, 6 August 2015

2015-08-06T08:52:10Z

← Older revision		Revision as of 09:52, 6 August 2015
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	===Reduction to the pole===		===Reduction to the pole===
	The residual magnetic intensity was reduced to the pole using a ~~2-D~~ frequency domain operator, working from the gridded values of the levelled magnetic data. The calculation, assuming all induced magnetization, was based on the following magnetic field parameters:		The residual magnetic intensity was reduced to the pole using a 2D frequency domain operator, working from the gridded values of the levelled magnetic data. The calculation, assuming all induced magnetization, was based on the following magnetic field parameters:
	* Magnetic declination: 2.5°W.		* Magnetic declination: 2.5°W.
	* Magnetic field inclination 65.5°N.		* Magnetic field inclination 65.5°N.
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	The frequency domain grid for the total field was computed by use of the transfer function below:		The frequency domain grid for the total field was computed by use of the transfer function below:
	{{clear}}		{{clear}}
	[[Image:14014 math1.png\|frameless\|~~center~~\|400px\| ]]		[[Image:14014 math1.png\|frameless\|left\|400px\| ]]
	{{clear}}		{{clear}}

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	{{clear}}		{{clear}}
	[[Image:14014 math1a.png\|frameless\|~~center~~\|120px\| ]]		[[Image:14014 math1a.png\|frameless\|left\|120px\| ]]
	{{clear}}		{{clear}}

Dbk: Protected "OR/14/014 Part 3: Data processing" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

2015-05-05T15:07:08Z

Protected "OR/14/014 Part 3: Data processing" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

← Older revision		Revision as of 16:07, 5 May 2015
(No difference)

Dbk: /* Horizontal gradient gridding */

2015-04-13T11:47:25Z

Horizontal gradient gridding

← Older revision		Revision as of 12:47, 13 April 2015
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	{{clear}}		{{clear}}
	[[Image:14014 math1a.png\|frameless\|center\|~~100px~~\| ]]		[[Image:14014 math1a.png\|frameless\|center\|120px\| ]]
	{{clear}}		{{clear}}

Dbk: /* Horizontal gradient gridding */

2015-04-13T11:47:14Z

Horizontal gradient gridding

← Older revision		Revision as of 12:47, 13 April 2015
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	{{clear}}		{{clear}}
	[[Image:14014 math1a.png\|frameless\|center\|~~200px~~\| ]]		[[Image:14014 math1a.png\|frameless\|center\|100px\| ]]
	{{clear}}		{{clear}}

Dbk: /* Horizontal gradient gridding */

2015-04-13T11:46:41Z

Horizontal gradient gridding

← Older revision		Revision as of 12:46, 13 April 2015
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	The frequency domain grid for the total field was computed by use of the transfer function below:		The frequency domain grid for the total field was computed by use of the transfer function below:
	{{clear}}		{{clear}}
	[[Image:14014 math1.png\|~~thumb~~\|center\|~~500px~~\| ]]		[[Image:14014 math1.png\|frameless\|center\|400px\| ]]
	{{clear}}		{{clear}}

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	{{clear}}		{{clear}}
	[[Image:14014 math1a.png\|~~thumb~~\|center\|200px\| ]]		[[Image:14014 math1a.png\|frameless\|center\|200px\| ]]
	{{clear}}		{{clear}}

Dbk: /* Horizontal gradient gridding */

2015-04-13T11:45:46Z

Horizontal gradient gridding

← Older revision		Revision as of 12:45, 13 April 2015
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	{{clear}}		{{clear}}

	where kx and ky were the wave numbers in the x and y directions and k2 was ~~<math>''kx<sup>2</sup>'' + ''ky<sup>2</sup>''</math>~~. This transform was computed for every point in the frequency domain except kx=ky=0. This point represented the DC value of the total field, which was computed by calculating the average total field value for the survey area.		where kx and ky were the wave numbers in the x and y directions and k2 was:

			{{clear}}
			[[Image:14014 math1a.png\|thumb\|center\|200px\| ]]
			{{clear}}

			This transform was computed for every point in the frequency domain except kx=ky=0. This point represented the DC value of the total field, which was computed by calculating the average total field value for the survey area.

	The reverse FFT was then computed for the above frequency domain grid and the DC value above added.		The reverse FFT was then computed for the above frequency domain grid and the DC value above added.

Dbk: /* Gridding */

2015-04-13T10:54:42Z

Gridding

← Older revision		Revision as of 11:54, 13 April 2015
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	===Gridding===		===Gridding===
	Levelled data were then gridded to produce 2D maps of the data. Refer to Table A5.1 in Appendix 4 for gridding parameters.		Levelled data were then gridded to produce 2D maps of the data. Refer to Table A5.1 in [[OR/14/014_Appendix_4:_Gridding_parameters \| Appendix 4]] for gridding parameters.

	===Residual magnetic intensity===		===Residual magnetic intensity===

Dbk: /* Removal of system Parallax and Heading */

2015-04-13T10:53:18Z

Removal of system Parallax and Heading

← Older revision		Revision as of 11:53, 13 April 2015
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	The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and calibration \| Tests and calibration]].		The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and calibration \| Tests and calibration]].

	Parallax corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #PARALLAX CONTROL \| Parallax Control. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| Heading Test]].		Parallax corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #PARALLAX CONTROL \| Parallax Control]]. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| Heading Test]].

	===Correction for temporal magnetic ('Diurnal') variation===		===Correction for temporal magnetic ('Diurnal') variation===

Dbk: /* Removal of system Parallax and Heading */

2015-04-13T10:52:56Z

Removal of system Parallax and Heading

← Older revision		Revision as of 11:52, 13 April 2015
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	===Removal of system Parallax and Heading===		===Removal of system Parallax and Heading===
	The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and calibration \| ~~Section 3.4~~]].		The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and calibration \| Tests and calibration]].

	Parallax corrections were applied to the data as per the tests carried out and detailed in ~~Section 3.4.2.2 above~~. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| ~~Section 3.4.2.3~~]].		Parallax corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #PARALLAX CONTROL \| Parallax Control. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| Heading Test]].

	===Correction for temporal magnetic ('Diurnal') variation===		===Correction for temporal magnetic ('Diurnal') variation===

Dbk: /* Removal of system Parallax and Heading */

2015-04-13T10:50:34Z

Removal of system Parallax and Heading

← Older revision		Revision as of 11:50, 13 April 2015
Line 7:		Line 7:

	===Removal of system Parallax and Heading===		===Removal of system Parallax and Heading===
	The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and ~~calibrations~~ \| Section 3.4]].		The instruments recording magnetic intensity, magnetic gradient and various altitude parameters are at physically different locations to the instrument recording the aircraft position. In addition, each instrument requires a slightly different amount of time to process its raw inputs (frequency, voltage, etc.) and compute the raw data recorded by the acquisition system. The cumulative result of these effects is that data readings are recorded at a different time position to that at which they were actually acquired. As a result, the position with which they are recorded is offset in time from the position at which they were acquired. In order to correct for this discrepancy, a time offset is applied to the data readings to restore them to their correct time and thus location. The required offsets for each aircraft and each instrument are determined in field tests as described in [[OR/14/014_Part_2:_Survey_logistics #Tests and calibration \| Section 3.4]].

	Parallax corrections were applied to the data as per the tests carried out and detailed in Section 3.4.2.2 above. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| Section 3.4.2.3]].		Parallax corrections were applied to the data as per the tests carried out and detailed in Section 3.4.2.2 above. Heading corrections were applied to the data as per the tests carried out and detailed in [[OR/14/014_Part_2:_Survey_logistics #HEADING TEST \| Section 3.4.2.3]].