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Arbejdsgruppemøde - SkyTEM processering Esben Auken and Nikolaj Foged ydroGeophysics Group epartment of Earth Sciences, University of Aarhus, Denmark ww.hgg.au.dk
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Arbejdsgruppemøde - SkyTEM processering
Esben Auken and Nikolaj Foged
HydroGeophysics GroupDepartment of Earth Sciences, University of Aarhus, Denmarkwww.hgg.au.dk
Dagsorden Intro til processering
Import: stack division, fortegn og linie fil, +30 sekunder
Processeringsvindue: højdeprocessering, midlingsfiltre, genkørsel
Manuel klipning af data: rådata versus average data
Workflow: • Koblinger fjerne fra raw data• Støjbeskæring i average• Fast inversion • Evaluering og justering af processering
Nye data - tæt sampling til tidlige tider - ny software - nyt møde
Processing, Inversion and Management of SkyTEM Data
Esben Auken and Kurt Sørensen
HydroGeophysics GroupDepartment of Earth Sciences, University of Aarhus, Denmarkwww.hgg.au.dk
Outline What is in the database?
Pitch and roll correction
Data filtering
Implementation in the Aarhus Workench
Ensuring Best Possible Data Quality Obtain maximum information about the Earth resistivity
distribution
5% data reproducibility of SkyTEM data on national test site
5% repeatability at each take off and landing
Accurate data processing and inversion
Data Basis Data types measured by the system
• GPS – 2 per sec.• Tilt of transmitter frame – 1.5 per sec. in in- and off-flight
directions• Laser altitude – 20 per sec. from two devices• Transmitter current – 1 per dataset• Single decays from 2 or more receiver channels – 40-120 Mb
per hour
Data Processing Voltage data and altitudes corrected with respect to the
tilt of the frame
To some degree manual intervention is necessary for• Altitudes • Culling of distorted data caused by coupling to wires and
fences
Data are not leveled
Altitude and Tilt Correction ”Normal” situation
Tx
R x
G round
1
lTx
R x
G round
1
l
Altitude and Tilt Correction ”Normal” situation
Tx
R x
G round
1
Tx A lt
l
Altitude and Tilt Correction ”Normal” situation – modelled in the inversion
Tx
R x
G round
1
Tx A lt R x A lt
l
Altitude and Tilt Correction ”Field” situation
G round
2
Altitude and Tilt Correction ”Field” situation
G round
2
Tx A lt
l
Altitude and Tilt Correction ”Field” situation
G round
2
Tx A lt
Altitude and Tilt Correction ”Normal” situation – modelled in the inversion
G round
2
Tx A lt R x A lt
R xl cos
Tilt data 5 min 3.5 line km
Tilt of +/-10° correction of voltage data
Time
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Tilt [D
eg
ree
s]
10.0
8.0
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
Time
10
:16
:30
10
:16
:20
10
:16
:10
10
:16
:00
10
:15
:50
10
:15
:40
10
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10
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:10
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:00
10
:14
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10
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10
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10
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:20
10
:14
:10
10
:14
:00
10
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:50
10
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:40
10
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:30
10
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10
:13
:10
10
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:00
10
:12
:50
10
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:40
10
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:30
10
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:20
10
:12
:10
10
:12
:00
10
:11
:50
10
:11
:40
Tilt [D
eg
ree
s]
10.0
8.0
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
Time
10
:16
:30
10
:16
:20
10
:16
:10
10
:16
:00
10
:15
:50
10
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:40
10
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:30
10
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10
:15
:10
10
:15
:00
10
:14
:50
10
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:40
10
:14
:30
10
:14
:20
10
:14
:10
10
:14
:00
10
:13
:50
10
:13
:40
10
:13
:30
10
:13
:20
10
:13
:10
10
:13
:00
10
:12
:50
10
:12
:40
10
:12
:30
10
:12
:20
10
:12
:10
10
:12
:00
10
:11
:50
10
:11
:40
Tilt [D
eg
ree
s]
10.0
8.0
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
y-tilt +/- 4°x-tilt +/- 8°Filtered
Altitude Processing
Time
10
:16
:30
10
:16
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10
:16
:10
10
:16
:00
10
:15
:50
10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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:00
10
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10
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:40
Altitu
de
[m]
60.0
55.0
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
Time
10
:16
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10
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10
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10
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:00
10
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10
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Altitu
de
[m]
60.0
55.0
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
Time
10
:16
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10
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10
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:10
10
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:00
10
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10
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10
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10
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10
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10
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10
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10
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10
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10
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:40
Altitu
de
[m]
60.0
55.0
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
Time
10
:16
:30
10
:16
:20
10
:16
:10
10
:16
:00
10
:15
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10
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10
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10
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Altitu
de
[m]
60.0
55.0
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
Raw Laser 1Raw Laser 2Removed by filteringFinal – tilt corrected and relocated
Removal of laser reflection from tree tops
Correction of altitudes for tilt – non perpendicular reflections from the ground
Relocation of altitudes to center of Tx and Rx coils
Laser reflections from tree tops
Difference due to high y-tilt
5 min 3.5 line km
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Box average – Narrow/Wide SkyTEM data example (Airborne TEM)
30s ~ 400m
SkyTEM data, 2 min ~ 1.5 Km
5s ~ 65 m
gate 1 gate 2 gate 3 . . . . . . . gate n
Box average – Narrow/Wide
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Raw
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Raw
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Average
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Average
30 s
5 s
2 min ~ 1.5 Km
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Trapezoid shaped average combines the best from the narrow and the wide box
average
used for SkyTEM data
Trapezoid shaped average
Box shaped average
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Average
Trapezoid shaped average
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Average
Time14:29:5014:29:4014:29:3014:29:2014:29:1014:29:0014:28:5014:28:4014:28:3014:28:2014:28:1014:28:00
Log
- N
o U
nit
1e+00
1e+01
1e+02
1e+03
1e+04
1e+05
Average
Trapezoid average - Sounding view
Trapezoid averageBox average, medium width
Trapezoid average - Sounding view
Trapezoid average
Box average, medium width
3-4 gates culled
Only 2 gates culled
High lateral resolution
Summary Shallow part of model section/early time gates
• maximum lateral resolution is obtain with a narrow data average
• large data stack is not needed because of a high signal to noise ratio
Deep part of model section/late time gates• Wide data average suppress the background noise and
increase penetration depth.• Wide data average does not reduce the lateral resolution
Trapezoid shaped average• maximum lateral resolution • maximum penetration depth• Could be applied to any continuous TEM-method
Summary Frame tilt is used for correction of altitudes and voltage
data
Coupled data are culled before inversion
Data average using trapezoid shaped filters and pruning
