URUANA 2026 — THREE-MODEL VECTOR AUDIT
Frozen center: -16.0593, -46.2585

IMPORTANT NOAA SIGN CONVENTION
Z positive = downward into Earth.
Z negative = upward away from Earth.
All three models at Uruana have Z ~ -12.8 microtesla and inclination ~ -33 deg:
the local field vector points upward by about 33 deg from the horizontal.

CENTER FIELD GEOMETRY
IGRF2025: D=-22.546390 deg, I=-33.027946 deg
WMM2025:  D=-22.562644 deg, I=-33.024956 deg
WMMHR2025:D=-22.565616 deg, I=-33.015444 deg

FULL N-S GRADIENT VECTORS (nT/km)
IGRF:  (np.float64(3.279192), np.float64(-1.27074), np.float64(3.310668))
WMM:   (np.float64(3.261565), np.float64(-1.274607), np.float64(3.292682))
WMMHR: (np.float64(3.152388), np.float64(-1.502944), np.float64(2.972344))

IGRF vs WMM gradient angle = 0.123459 deg
IGRF vs WMMHR gradient angle = 4.304179 deg
WMM vs WMMHR gradient angle = 4.192355 deg

WMMHR - IGRF gradient increment:
(np.float64(-0.126804), np.float64(-0.232205), np.float64(-0.338324)) nT/km
WMMHR - WMM gradient increment:
(np.float64(-0.109177), np.float64(-0.228337), np.float64(-0.320338)) nT/km

Thus the negative Z-gradient increment is present against BOTH low-resolution/main-field baselines.
The IGRF and WMM gradients are almost collinear (~0.12 deg apart), while WMMHR rotates
the gradient by ~4.2-4.3 deg. This supports describing the HR directional signature as
baseline-robust at this grid scale.

CRITICAL DISTINCTION
The ABSOLUTE field vector B points upward (negative Z) in all models.
This is normal geomagnetic geometry in this part of the Southern Hemisphere and is not by itself
a local anomaly.

At the frozen center, WMMHR has a less-negative Z than WMM, so the pointwise WMMHR-WMM
correction itself does NOT make the absolute field more upward; it makes inclination slightly
less negative (closer to horizontal) by about
34.241 arcsec.

What points upward is the NORTHWARD SPATIAL CHANGE of the HR increment:
d/dN[(B_WMMHR - B_baseline)] has a negative Z component for either IGRF or WMM baseline.
These are different vectors and must not be conflated.