Doubling the spectrum of time-domain induced polarization by harmonic de-noising, drift correction, spike removal, tapered gating and data uncertainty estimation

Investigations of a Cretaceous limestone with spectral induced polarization and scanning electron microscopy

“…Furthermore, the processing applies a despiking algorithm and an improved estimate of the background drift which can handle also non-linear drift cases such as electrode polarization effects. This improved drift estimate ensures a more accurate recovery of the IP decay shape (and thus spectral IP content) at late times compared to the normally used linear background drift estimate (see Olsson et al 2016). Data examples of the difference in time ranges obtained before and after the signal processing scheme are visualized in Fig.…”

“…3), the DCIP results were also compared to satellite images in order to identify possible 3D-effects in the inverted models. Olsson et al (2016). Due to the challenging urban setting in the main survey area with buried infrastructure and electromagnetic noise, a reference DCIP profile was also carried out with the same measurement setup and settings. The reference line was located at a distance of approximately 4 km north of the main survey area (see Fig.…”

“…However, the collection of full-waveform data in this survey enabled the possibility to regate the IP decays after the measurements. A processing scheme recently developed by Olsson et al (2016) was used to recover data from early times and increase the spectral information content of the IP decays. This processing scheme applies a model based harmonic denoizing for supressing the periodic noise which reduces the need for long (60 ms) gates and makes it is possible to retrieve the decay information from one to two milliseconds after the current pulse.…”

“…The time domain IP data measured in the current survey were processed with a novel approach presented by Olsson et al (2016), which enabled early IP decay times to be recovered. In this way, the spectral range of the time decays increased despite the short acquisition times that had been used during the field acquisition, and the data could be inverted for spectral Cole-Cole parameters (Fiandaca et al 2012Auken et al 2014).…”

BeFo 382 - Detailed Comparison Study of 3D-characterized Rock Mass and Geophysical Models

“…A Terrameter LS with modified input filters was used for measuring potentials and for transmitting a 100% duty-cycle current with a pulse duration of four seconds. Resistivity and integral chargeability (0.014 to 3.7 s) data were extracted from the full waveform recordings using recent developments in full waveform signal processing (Olsson et al, 2016). The pre-processed field data were inverted with robust L1-norm and vertical, horizontal, diagonal and cross-diagonal regularization in Res3Dinv (v. 3.11.62) for a subsurface discretized in 160 by 20 1x1-meter horizontal cells and 13 layers with log-increasing cell depth.…”