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), Am 2 High moment (HM), Am 2 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

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 Line1A Line 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 m 35 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  s Altitude ~15 m Raw data

Repeatability, 15 m, data space 115  s Altitude ~15 m Raw data

Repeatability, 15 m, data space 115  s Altitude ~15 m Raw data

Repeatability, altitude 15 m 115  s Altitude ~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

Match to reference section, 15 m 14  s 3.6 ms 115  s 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