An integrated processing scheme for high-resolution airborne electromagnetic surveys, the SkyTEM system

TLDR

The techniques developed for SkyTEM are generally applicable to airborne electromagnetic surveys, including altitude filtering for any airborne system. The SkyTEM helicopter‑borne transient electromagnetic system, developed in 2004, incorporates devices that model its airborne movement to produce high‑resolution subsurface images and is supported by an integrated processing and inversion system. Altitude data are recursively filtered to remove tree reflections, raw voltage data are culled and geometrically corrected for pitch and roll, and the data are de‑spiked and averaged with trapezoid‑shaped kernels before a laterally constrained smooth‑model inversion evaluates and finalizes the processing. The SkyTEM system produces unbiased data beginning 10–12 µs after transmitter current turn‑off.

Abstract

The SkyTEM helicopter-borne transient electromagnetic system was developed in 2004. The system yields unbiased data from 10 to 12 μs after transmitter current turn-off. The system is equipped with several devices enabling a complete modelling of the movement of the system in the air, facilitating excellent high-resolution images of the subsurface.An integrated processing and inversion system for SkyTEM data is discussed. While the authors apply this system with SkyTEM data, most of the techniques are applicable for airborne electromagnetic data in general. Altitude data are processed using a simple recursive filtering technique that efficiently removes reflections from trees. The technique is completely general and can be used to filter altitude data from any airborne system. Raw voltage data that are influenced by electromagnetic coupling to man-made structures are culled from the dataset to avoid uncoupled data being distorted by coupled data, and geometrical corrections are applied to correct for pitch and roll of the transmitter frame. Data are de-spiked and averaged using trapezoid-shaped filter kernels. A Laterally Constrained Inversion using smooth models is actively used to evaluate the processing, and the final inversion is tightly connected to the processing procedures.