Physics & Scientific Methods
This directory documents the scientific methods and modelling approaches implemented in YmerFlow's processing pipelines. Each document covers a self-contained group of processes, including the mathematical formulations, algorithms, and links to relevant peer-reviewed literature.
Pipelines
Airborne Electromagnetics (AEM)
| Document | Description |
|---|---|
| AEM Data Processing | Corrections (altitude/topo, tilt, moving average), noise modelling, and data culling (roll/pitch/alt, STD, slope, curvature, geometry) |
| AEM Inversion & Forward Modelling | 1D layered EM inversion (SimPEG), dual-moment system description (SkyTEM), regularization, IRLS, forward modelling |
| AEM 3D Gridding | Step-function vertical assignment and 3D interpolation (scipy/pyinterp) of layered resistivity models to regular voxel grids |
AEM pipeline: Import (XYZ/GEX or msgpack) → Processing → Inversion → Forward modelling → 3D Gridding
Airborne Magnetics
| Document | Description |
|---|---|
| Magnetics Processing | QC filters: 4th difference noise, diurnal chord analysis, drape analysis, Butterworth filters (derived from GSC standards) |
| Magnetics Inversion | Equivalent source gridding (flat-layer dipole inversion) and full 3D OcTree inversion (susceptibility/MVI/amplitude) via SimPEG |
Magnetics pipeline: Import (CSV) → Processing (QC) → Equivalent source gridding → 3D inversion
Infrastructure
| Document | Description |
|---|---|
| Common Infrastructure | Sensitivity matrix caching, data formats (msgpack, webxtile), entry-point registration, swaggerspect schema generation |
Key References
- AEM layered inversion: Auken, E., Christiansen, A. V., Westergaard, J. H., Kirkegaard, C., Foged, N., & Viezzoli, A. (2009). "An integrated processing scheme for high-resolution airborne electromagnetic surveys, the SkyTEM system." Exploration Geophysics, 40(2), 184-192. DOI: 10.1071/eg08128
- Magnetic Vector Inversion (MVI): Lelièvre, P. G., & Oldenburg, D. W. (2009). "A 3D total magnetization inversion applicable when significant, complicated remanence is present." Geophysics, 74(3), L21-L30. DOI: 10.1190/1.3103249
- Amplitude magnetic inversion: Li, Y., Oldenburg, D. W., Farquharson, C. G., & Shekhtman, R. (2017). "Magnetic amplitude inversion for determining magnetization." Geophysics, 82(2). DOI: 10.1190/geo2016-0302.1
- IRLS sparse regularization: Farquharson, C. G., & Oldenburg, D. W. (1998). "Non-linear inversion using general measures of data misfit and model structure." Geophysical Journal International, 134(1), 213-227. DOI: 10.1046/j.1365-246x.1998.00555.x
- SimPEG framework: Cockett, R., Kang, S., Heagy, L. J., Pidlisecky, A., & Oldenburg, D. W. (2015). "SimPEG: An open source framework for simulation and gradient based parameter estimation in geophysical applications." Computers & Geosciences, 85, 142-154. DOI: 10.1016/j.cageo.2015.09.015
- Aarhus Workbench: Auken, E., Foged, N., & Sørensen, K. I. (2002). "Model recognition by 1-D laterally constrained inversion of resistivity data." Geophysics, 67(5), 1468-1475. DOI: 10.1190/1.1512750
- GSC magnetic QC: Geological Survey of Canada, standard magnetic QC procedures (4th difference noise, diurnal chord analysis).