{
 "schema": "ausmt-station",
 "version": "0.1",
 "ausmt_id": "au.cicada97-1997-98.CNB",
 "station": "CNB",
 "survey": "CICADA97 induction array 1997-98",
 "survey_id": "cicada97-1997-98",
 "country": "Australia",
 "organisation": "Australian National University",
 "location": {
  "lat": -35.315,
  "lon": 149.363333
 },
 "data": {
  "type": "GDS",
  "n_periods": 20,
  "period_min_s": 10.0,
  "period_max_s": 6826.870563
 },
 "diagnostics": {
  "median_relative_error": null,
  "remote_reference": false,
  "tipper_available": true,
  "completeness_smoothness_diagnostic": {
   "value": null,
   "basis": "s",
   "note": "not a quality or geological-value judgement"
  },
  "method": "phase-tensor (Caldwell 2004)",
  "note": "screening diagnostic, not an interpretation product"
 },
 "processing": {
  "software": null,
  "algorithm": null,
  "remote_reference": false,
  "remote_site": null,
  "file_written_by": {
   "name": null,
   "version": null
  },
  "note": "Tipper transfer functions minted from Hitchman, A. P. (1999) 'Interactions\nbetween aeromagnetic data and electromagnetic induction in the earth', PhD\nthesis, The Australian National University, hdl:1885/147975, Table B.2\n(printed 169 to 172), with station positions and elevations from Table 6.2\n(printed 47). Transcription:\nGDS/inventories/hitchman1999_cicada97_table_b2_transfer_functions.csv and\nGDS/inventories/hitchman1999_cicada97_stations.csv, both read off 300 dpi\npage renders rather than off the scan's text layer.\n\nREFERENCE SITE, AND WHAT IT MEANS FOR MAGNITUDE.  These are NOT local\ntippers. The Table B.2 caption and Chapter 6 (printed 50) state that the\nhorizontal variations recorded at CNB, the Canberra Magnetic Observatory,\nwere used to represent the source field at every site, so each value relates\nthe LOCAL vertical field to the horizontal field at CNB rather than to the\nhorizontal field beneath the instrument:\nz(t) at this site = P . x(t) at CNB + Q . y(t) at CNB\nA local tipper is bounded near unity by the physics of a layered earth.  A\nremotely referenced transfer function is not, because the source-field ratio\nbetween two separated sites is itself part of the quantity.  Magnitudes near\nand above 1.0 are therefore EXPECTED here and are not defects: the largest\nreal arrow in this campaign is 1.33, at 1280 s at the continental-slope site\nSolo, which holds above 1.0 at every period from 426.7 s upward.  Do not\ncompare these values against a locally referenced tipper without carrying\nthe reference. CNB itself is in this survey and is self-referenced, so its\nown values are a measure of the observatory against itself and are the\nsmallest in the campaign.\n\nCONVENTION, AND THE TRAP IT AVOIDS.  Every row of Table B.2 prints an\ninduction arrow (Lr, theta_r, Lq, theta_q) beside the transfer functions it\nderives from (Pr, Pq, Qr, Qq).  The thesis symbol list (printed xv to xvi)\nand Equation 3.2 (printed 27) define P as the geographic-NORTH transfer\nfunction and Q as the geographic-EAST one, with subscript r the real part\nand q the quadrature part, in the frame with x geographic north, y\ngeographic east and z positive down.  That is the EDI tipper's own frame, so\nthe mapping is direct and no sign is changed:\nTXR = Pr    TXI = Pq    TYR = Qr    TYI = Qq\nSection 5.2.4 (printed 42) says the ARROWS were reversed 'in accordance with\nthe convention that Parkinson induction arrows point toward a nearby\nconductor'.  The reversal therefore lives in the printed arrow azimuth and\nNOT in P and Q.  Tested over all 129 rows of this table whose real arrow\nreaches 0.10, the printed theta_r equals atan2(Qr, Pr) plus 180 degrees in\nevery single case and equals it without the 180 in none, and the 90\nqualifying quadrature rows behave the same way.  Deriving a tipper from the\narrow columns would publish every value in this survey rotated by 180\ndegrees.  The arrow columns are not used here.\n\nThe result is checked against physics and against this collection.  Taking\nthe printed P and Q as written, the Parkinson form of the real arrow points\nbetween 129 and 149 degrees true at every land site and at Solo, that is,\noffshore into the Tasman Sea, and its magnitude climbs from 0.18 inland to\n0.68 at the coast and 1.23 at the shelf edge before collapsing to 0.14 and\n0.05 at the two abyssal sites, which sit beneath the conductor rather than\nbeside it.  That is the coast effect.  Compared against the compilation\nregister's own arrows at the six re-occupied sites, over periods of an hour\nand longer, the two occupations agree to within 0.5 to 4.5 degrees at the\nfour sites nearest the coast, and to 8 and 18 degrees at the two inland\nsites, where the arrow is shortest and its azimuth least determined.  A\nreversed convention would show as a disagreement near 180 degrees, and\nnothing in that comparison is anywhere near it.\n\nFRAME: geographic.  Table B.2 was derived in the geomagnetic frame and\nrotated to geographic using the AGRF95 declinations of Table B.1, so the\nrotation is the thesis's own and this generator applies none.  Arrow\nazimuths in the printed table are degrees clockwise from geographic north.\n\nUNCERTAINTIES.  Table B.2 prints two error columns, both headed 'e', one\ninside the P group and one inside the Q group.  The caption states that each\nis a STANDARD ERROR and that it applies to BOTH the real and the quadrature\npart of its own pair.  TXVAR.EXP and TYVAR.EXP hold a variance, so this file\nwrites\nTXVAR.EXP = e_P squared        TYVAR.EXP = e_Q squared\nand nothing else: there is no confidence-limit conversion, because the table\nprints none, and no split between the real and quadrature parts, because the\ncaption forbids one.  These are real published uncertainties, not a constant\nfill, and they are the reason the variance blocks are present here where\nthey are absent from other minted files in this collection.\n\nERROR FLOOR.  Twenty-one of this table's error cells print 0.00.  That is a\ntwo-decimal rounding of an error below 0.005, not a claim of perfect\ndetermination, and fourteen of them are at CNB, the reference site itself.\nA printed 0.00 is written here as a variance of 0.005 squared, that is\n2.5E-05, which is the smallest error the print could have rounded to zero\nfrom.  Writing a zero variance would publish an infinite weight on a rounded\nnumber.  The substitution is applied to those cells only; every other\nvariance in this file is the printed error squared, untouched.\n\nIMPEDANCE AND CHANNELS.  None.  CICADA97 deployed three-component\nmagnetometers and recorded no electric field, so this file declares HX, HY\nand HZ only and carries no impedance block, no apparent resistivity, no\nphase and no electric channel of any kind.  Nothing here may be read as\nmagnetotelluric data.\n\nCAMPAIGN: CICADA97, a ten-site vertical-field induction array run from the\nResearch School of Earth Sciences of The Australian National University down\nthe New South Wales south coast and out onto the Tasman abyssal plain.  Land\nrecording opened 30 September 1997 with a second deployment from 18 October\n1997, and BBB was re-occupied 13 to 18 February 1998.  Land instruments were\nFlinders three-component ringcore fluxgates after Chamalaun and Walker\n(1982) sampling at 5 s; CNB is a Narod fluxgate at 1 s.  No per-station\nacquisition date is printed, so ACQDATE is deliberately absent rather than\nfilled with a boilerplate value.\n\nSTATION: Canberra, thesis site code CNB, Canberra Magnetic Observatory,\nAustralian Capital Territory. Table 6.2 position -35.31500, 149.36333,\nelevation 859 m. The 20 rows are this station's block of Table B.2, 6826.7 s\ndown to 10.0 s.\n\nCOORDINATES: Table 6.2 states that every position is GPS 'with the exception\nof CNB', whose position is taken from Hopgood and McEwin (1997).\n\nERROR FLOOR APPLIED at 26.7 s, 40.0 s, 53.3 s, 80.0 s, 106.7 s, 160.0 s,\n213.3 s, 320.0 s, 426.7 s, where the print rounds an error to 0.00.\n\nRE-OCCUPATION: this site was occupied fourteen years earlier by the Tasman\nProject of Seafloor Magnetotelluric Exploration and is published in this\ncollection as au.tasman-land-1983-84.Bungendore, 0.40 km away. That\nseparation is measured when this file is written, between the Table 6.2\nposition above and the position the earlier record carries in the corpus,\nwhich is stored to 3 decimal degrees, about 0.11 km.  It is therefore the\ndifference between what the two campaigns recorded, not an artefact of the\nstored precision and not a disagreement to be reconciled: each occupation\nset up its own site fourteen years apart. That record and this one are\nDISTINCT OCCUPATIONS by different instruments in different years, and\nneither supersedes the other: this one reaches down to 10 s where the\nearlier one stops near an hour.  The cross-reference is given so a consumer\ncan join them deliberately; the two are never merged and are never\ndeduplicated on proximity. Also published as au.awags-1989-90.CNB, 0.40 km\naway, which is a third occupation of the same observatory.  Note that the\nstation published as au.tasman-land-1983-84.Canberra is NOT this site: that\nis Ferguson's BKM, a separate field station 24.49 km away.\n\nThis file is published as station au.cicada97-1997-98.CNB. Dates in this\nfile are ISO 8601."
 },
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  "license": "CC-BY-4.0",
  "edi_path": "edi/cicada97-1997-98/CNB.edi"
 },
 "provenance": {
  "pipeline": "ausmt/extract.build_portal",
  "pipeline_version": "0.2.1",
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  "software": {
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   "mt_metadata": "1.0.10",
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  "parameters": {
   "dimensionality": {
    "beta_per_period_deg": 3.0,
    "skew_3d_deg": 5.0,
    "pct_periods_3d_threshold": 40,
    "ellip_2d_deg": 0.1,
    "min_rez_row_sine": 0.01,
    "beta_physical_cap_deg": 15.0,
    "min_usable_period_frac": 0.5,
    "skew_aggregation": "median"
   },
   "diagnostic": "completeness/smoothness (median rel error + coverage + smoothness)"
  },
  "generated": "2026-09-09T06:22:47.791693+00:00",
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 "coordinate_qc": null,
 "canonical_conditioning": null,
 "frame": {
  "evidence": {
   "branch": "mt",
   "zrot": null,
   "trot": null,
   "rotspec": null,
   "hmeas_azimuths": {
    "hx": 0.0,
    "hy": 90.0
   },
   "emeas_azimuths": {
    "ex": null,
    "ey": null
   }
  },
  "impedance_rotation_deg_source": null,
  "tipper_rotation_deg_source": null,
  "derotated": false,
  "frame_served": "declared-zero",
  "declared_azimuth_deg": 0.0,
  "convention_check": {
   "verdict": "insufficient",
   "phs_xy_median_deg": null,
   "phs_yx_median_deg": null,
   "n_periods_used": 0,
   "detail": "only 0 usable period(s) (< 5) — no convention verdict"
  }
 },
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