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Arbejdsgruppemøde - SkyTEM processering

Arbejdsgruppemøde - SkyTEM processering. Esben Auken and Nikolaj Foged. HydroGeophysics Group Department of Earth Sciences, University of Aarhus, Denmark www.hgg.au.dk. Dagsorden. Intro til processering Import: stack division, fortegn og linie fil, +30 sekunder

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Arbejdsgruppemøde - SkyTEM processering

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  1. Arbejdsgruppemøde - SkyTEM processering Esben Auken and Nikolaj Foged • HydroGeophysics Group • Department of Earth Sciences, University of Aarhus, Denmark • www.hgg.au.dk

  2. 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

  3. Processing, Inversion and Management of SkyTEM Data Esben Auken and Kurt Sørensen • HydroGeophysics Group • Department of Earth Sciences, University of Aarhus, Denmark • www.hgg.au.dk

  4. Outline • What is in the database? • Pitch and roll correction • Data filtering • Implementation in the Aarhus Workench

  5. 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

  6. 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

  7. 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

  8. Altitude and Tilt Correction • ”Normal” situation

  9. Altitude and Tilt Correction • ”Normal” situation

  10. Altitude and Tilt Correction • ”Normal” situation – modelled in the inversion

  11. Altitude and Tilt Correction • ”Field” situation

  12. Altitude and Tilt Correction • ”Field” situation

  13. Altitude and Tilt Correction • ”Field” situation

  14. Altitude and Tilt Correction • ”Normal” situation – modelled in the inversion

  15. Tilt data • 5 min  3.5 line km • Tilt of +/-10°  3% correction of voltage data y-tilt +/- 4° x-tilt +/- 8° Filtered

  16. Raw Laser 1 Raw Laser 2 Removed by filtering Final – 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 Difference due to high y-tilt Laser reflections from tree tops Altitude Processing 5 min  3.5 line km

  17. 5s ~ 65 m 30s ~ 400m Box average – Narrow/Wide • SkyTEM data example (Airborne TEM) gate 1 gate 2 gate 3 . . . . . . . gate n SkyTEM data, 2 min ~ 1.5 Km

  18. Raw Average 30 s 5 s 2 min ~ 1.5 Km Box average – Narrow/Wide Raw Average

  19. Trapezoid shaped average • combines the best from the narrow and the wide box average • used for SkyTEM data Trapezoid shaped average Box shaped average

  20. Average Average Average Trapezoid shaped average

  21. Trapezoid average - Sounding view Box average, medium width Trapezoid average

  22. Trapezoid average - Sounding view Box average, medium width Trapezoid average High lateral resolution 3-4 gates culled Only 2 gates culled

  23. 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

  24. 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

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