AusMT survey data — licence and attribution
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Licence:     CC-BY-4.0
Licence URL: https://creativecommons.org/licenses/by/4.0/
Licensor:    Geological Survey of South Australia
Year:        2006

Attribution (cite as):
  Crabb, T.N.; Mortimer, L.; Doerner, W.; Maude, G. (2006) Black Hill 2005-06

This LICENSE.txt travels with the data files in this archive. The transfer functions were
distributed via the AusMT portal, which serves only openly licensed Australian magnetotelluric
releases; the licence above is the custodian's, set in the survey's survey.yaml. Reuse under the
terms of that licence (https://creativecommons.org/licenses/by/4.0/).

Changes were made: This release is a derived rendition in two classes, and every one of its 409 files declares which class it is under ausmt.station.tf_provenance. For the 229 contractor-processed stations: impedance tensors computed from the delivered cross-spectra and rotated from the acquisition frame into the standard magnetotelluric frame; stations named from the contractor's own SECTID; two defective coordinates repaired against the contractor's coverage tables. For the 180 figure-recovered stations: the custodian delivered no data at all, and the transfer functions were read from the sounding curve figures in the contractor's reports, taken from the PDF's own vector drawing operators and rebuilt as files. Those 180 carry the off diagonal impedance and the tipper only, because the figures plot no Zxx and no Zyy, so they have no diagonal impedance and no phase tensor and none is inferred; their uncertainty is the contractor's stated survey wide data accuracy rather than a per station measurement, and they carry no tipper uncertainty because the figures draw none. Every absent value in those files, the diagonal and the tipper uncertainty included, is written as the literal nan rather than as the format's EMPTY sentinel, which the common reader of this format turns into a measured zero; nan is not a token SEG EDI defines and a strict third party reader may object to it. Both classes are served in one frame, under one survey, with one station naming scheme.. AusMT serves derived renditions (canonical EMTF XML; MTH5 where available) generated from the deposited files; per-station conditioning notes are recorded in the machine-readable products.
