| Title | Joining multiple AEM datasets to improve accuracy, cross calibration and derived products: The Spiritwood VTEM and AeroTEM case study |
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| Author | Sapia, V; Viezzoli, A; Oldenborger, G |
| Source | Near Surface Geophysics vol. 13, no. 1, 2015 p. 61-72, https://doi.org/10.3997/1873-0604.2014041 |
| Image |  |
| Year | 2015 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140147 |
| Publisher | EAGE Publications |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Manitoba |
| NTS | 73G/05 |
| Area | Spiritwood Valley |
| Lat/Long WENS | -108.0000 -107.5000 53.5000 53.2500 |
| Subjects | hydrogeology; geophysics; e m surveys, airborne; magnetic field; conductivity; modelling; aquifers |
| Illustrations | magnetic maps; seismic reflection profiles |
| Program | Groundwater Geoscience Aquifer Assessment &
support to mapping |
| Released | 2010 02 01 |
| Abstract | Airborne time-domain electromagnetic methods (AEM) are useful for hydrogeological mapping due to their rapid and extensive spatial coverage and high correlation between measured magnetic fields,
electrical conductivity, and relevant hydrogeological parameters. However, AEM data, preprocessing and modelling procedures can suffer from inaccuracies that may dramatically affect the final interpretation. We demonstrate the importance and the
benefits of advanced data processing for two AEM datasets (AeroTEM III and VTEM) collected over the Spiritwood buried valley aquifer in southern Manitoba, Canada. Early-time data gates are identified as having significant flightdependent signal bias
that reflects survey flights and flight lines. These data are removed from inversions along with late time data gates contaminated by apparently random noise. In conjunction with supporting information, the less-extensive, but broader-band VTEM data
are used to construct an electrical reference model. The reference model is subsequently used to calibrate the AeroTEM dataset via forward modelling for coincident soundings. The procedure produces calibration factors that we apply to AeroTEM data
over the entire survey domain. Inversion of the calibrated data results in improved data fits, particularly at early times, but some flight-line artefacts remain. Residual striping between adjacent flights is corrected by including a mean empirical
amplitude correction factor within the spatially constrained inversion scheme. Finally, the AeroTEM and VTEM data are combined in a joint inversion. Results confirm consistency between the two different AEM datasets and the recovered models. On the
contrary, joint inversion of unprocessed or uncalibrated AEM datasets results in erroneous resistivity models which, in turn, can result in an inappropriate hydrogeological interpretation of the study area. |
| Summary | (Plain Language Summary, not published)
Airborne electromagnetic geophysics surveys are useful for aquifer mapping due to rapid and extensive spatial coverage. However, proper data processing
and modelling are required to ensure reliable products. We compare two different airborne electromagnetic datasets over the Spiritwood buried valley aquifer in southern Manitoba. We demonstrate the importance of data processing and calibration on the
resulting geological models and we discuss implications for hydrogeological interpretations. |
| GEOSCAN ID | 295055 |
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