Nikolaj Foged*, A.V. Christiansen**, and Esben Auken**HydroGeophysics Group, Department of Earth Sciences, Aarhus University, Denmark **Geological Survey of Denmark and Greenland - GEUS

Validating SkyTEM Data Against Ground-based TEM Data at the Danish National Test Site by Upward Continuation

z-receiver

z-receiver coil

x-receiver coil

Transmitter frame

instrumentation

• Super low moment (SLM), 45 000 Am2

• High moment (HM),180 000 Am2

• SLM + HM is applied sequential

SkyTEM at the extended Test site

Laser altimeters

inclinometers,pitch and roll

SkyTEM, extended Test site - dataset

• Altitudes: 15 m, 25 m, 35 m

• Four repetitions per line and altitude. Total of 12 repetitions per line

• Standard processing and inversion is applied

• Sounding/model spacing: 20 m

• Independent LCI-inversion of each line repetitions

1 km

Validation of SkyTEM - model space

Validation of SkyTEM - model space

• Repeated line, altitude 15 m

Line1A

Line 1B

Validation of SkyTEM - model space

• Repeated line, altitude 15 m

• Background: SkyTEM, Line 1A

• Front bars: SkyTEM, Line 1B

Line1ALine 1B

Validation of SkyTEM - model space

• Repeated line, altitude 15 m and 35 m

15 m

35 m

Validation of SkyTEM - model space

• Repeated line, altitude 15 m and 35 m

• Background: Altitude 15 m

• Front bars: Altitude 35 m

15 m35 m

Validation of SkyTEM - model space

• Comparison with ground based TEM: Altitude 15 m

SkyTEM

Ground TEM

Validation of SkyTEM - model space

• Comparison with ground based TEM: Altitude 15 m

• Background: SkyTEM, altitude 15 m

• Front bars: Ground based TEM

• Background: Altitude 35 m

• Front bars: Altitude 15 m

Validation of SkyTEM - model space

• Comparison with ground based TEM: Altitude 15 m, 35 m

• Background: SkyTEM, altitude 15 m, 35 m

• Front bars: Ground based TEM

15 m

35 m

Validation of SkyTEM - data space

Repeatability, 15 m, data space

115 sAltitude ~15 m

Raw data

Repeatability, 15 m, data space

115 sAltitude ~15 m

Raw data

Repeatability, 15 m, data space

115 sAltitude ~15 m

Raw data

Repeatability, altitude 15 m

115 sAltitude ~15 m

Raw data

Upward continuation to a nominal height

Forward 23.1 m, 25 m

Model Calculate correction factor per time gate

Data, 25 m

Apply correction factor to data

• How ?

Data, 23.1 m

Inversion

Upward continuation of ground based TEM

Forward, SkyTEM system, 25 m

Reference model

SkyTEM refe-rence responce

• To compare/evaluate the SkyTEM system with the ground based TEM in data space

• How ?

Ground TEM

Inversion

Repeatability, nomial altitude 15 m

115 s

Nominal altitude

Raw data

Repeatability, nomial altitude 15 m

14 s

3.6 ms

115 s

Repeatability, nomial altitude 15, 25, 35 m

115 s

Match to reference section, 15, 25, 35 m

115 s

Reference response

Reference response

Reference response

Match to reference section, 15 m

14 s

3.6 ms

115 s

Reference response

Reference response

Reference response

Conclusion• Calibration on the National test site insures

consistence mapping results

• Validation of the SkyTEM system

Repeatability - same altitude Repeatability - different altitudes Match to ground based TEM / reference

section

• Also validation of:• the detailed and carefull processing scheme • the high precision inversion code (em1dinv)

• Validation is demanded for any TEM-system to participate in the Danish groundwater mapping campaign

All data to nominal height of 25 m