URUANA 2026 — ROTATION-ONLY OBSERVABLE AUDIT
Frozen center: -16.0593, -46.2585

WMM baseline -> WMMHR:
  pointwise 3-D rotation angle at center = 0.010544 deg = 37.957 arcsec
  inclination change = 34.238 arcsec
  declination change = -10.692 arcsec
  tangential |delta B| = 4.321 nT
  radial delta B = -37.321 nT
  scalar delta F = -37.321 nT

IGRF baseline -> WMMHR:
  pointwise 3-D rotation angle at center = 0.020979 deg = 75.525 arcsec
  inclination change = 45.003 arcsec
  declination change = -69.207 arcsec
  tangential |delta B| = 8.598 nT
  radial delta B = -45.232 nT
  scalar delta F = -45.230 nT

N-S gradient of the pure rotation angle across each longitude (arcsec/km toward north):
  WMM: -2.9141, -2.6097, -1.5715, -0.2304
  WMM: sign consistent? YES
  IGRF: -1.9154, -1.0805, -0.2122, +0.5905
  IGRF: sign consistent? NO

Interpretation:
The rotation-only observable theta = arccos(Bhat_baseline · Bhat_HR) is invariant to a pure scalar rescaling of field magnitude.
Therefore non-zero theta proves that the higher-resolution model changes direction, not only intensity.
The signed delta-I and delta-D terms locate that rotation in vertical and horizontal angular coordinates.
This remains a regional model-scale signature, not a direct 0-8 km observation.