10. Stratagem Surveys#

The pycsamt.stratagem package covers the post-acquisition workflow for AMT surveys collected with Geometrics/EMI Stratagem hardware, from raw instrument output through to processed, georeferenced EDI files ready for EM Tools Guide or inversion. Stratagem hardware does not export EDI directly: each station is recorded as a set of whitespace-separated 19-column ASCII component files (frequency, stack count, cross-spectral values), and a separate desktop tool (WinGLink) converts those into EDI files with placeholder coordinates (LAT=0:00:00.00). Everything from that point on — reading the raw files for hardware-level QC, injecting real station coordinates from a GPS table, statistical QC, static-shift correction, frequency editing, noise removal, and final export/renaming — is what this package handles.

raw hardware files (X*.NNN, Y*.NNN, Z*.NNN)
  ↓  WinGLink (external tool, required once)
    ↓  EDIBatch / Sites        load & natural-sort the EDI export
      ↓  CoordinateInjector    inject GPS coords from CSV / XLS / XLSX
        ↓  QualityController   per-station QC report (optional)
          ↓  StaticShiftCorrector  AMA static-shift removal
            ↓  FrequencyFilter     band select + incoherent-freq masking
              ↓  NoiseRemover      powerline notch + Hampel + smoothing
                ↓  export() / rename()   write corrected, renamed EDIs

StratagemSurvey composes every step above into a single fluent pipeline, but each stage is also usable on its own — useful when a survey needs a non-standard station-count reconciliation, a custom coordinate table layout, or only a subset of the processing steps.

Real Stratagem deliveries are rarely clean: GPS tables often don’t have one row per station (calibration shots, repeat “check point” measurements, stations the instrument failed to record), coordinate columns can be mislabeled or shifted, and a bad GPS fix can sit undetected among hundreds of otherwise-good rows. This guide works through those cases directly rather than only the happy path.

Use this section when ingesting a new Stratagem field delivery, when GPS coordinates need reconciling against a field report before CoordinateInjector can run, or when composing the full raw-to-corrected-EDI pipeline with StratagemSurvey. Field-to-Inversion Case Study runs that same workflow as one visual, reproducible case study, using pycsamt.map and pycsamt.emtools to check the result at each step rather than only reading printed numbers. For the complete callable reference, see pycsamt.stratagem.