Estimation of the NAVD88 Bias Relative to the IHRF in Mexico Using Optimized Spatial Filtering

The estimation of the vertical datum potential in Mexico (Ŵ0NAVD88) and its geopotential bias (δŴ0) relative to the International Height Reference Frame (IHRF) is essential for integrating national vertical systems into a global reference frame. We propose a methodology based on GNSS observations, orthometric heights, and geoid undulations derived from two regional geoid models (xGGM23 and GGM25) and four high-resolution global geopotential models (WHU-CASM-UGM2025_2159, EIGEN-6C4, XGM2019e_2159, and SGG-UGM-2), combining adaptive spatial filtering with a weighting scheme that integrates spatial density and orthometric height. The results show consistent estimates of δŴ0 between −6.456 and −6.746 m2 s−2, corresponding to Ŵ0NAVD88 values between 62,636,859.856 and 62,636,860.146 m2 s−2. The formal SEM ranges from ±0.768 to ±1.060 m2 s−2 (≈8–11 cm) but quantifies formal precision only; the combined systematic error budget is ≈3.3 m2 s−2 (RSS) and exceeds the inter-model spread by an order of magnitude. Consequently, no hierarchical ranking is attributed to the six solutions. The methodology provides a reproducible framework for IHRF integration, and the reported δŴ0 values represent a national mean estimate; the spatial structure of the residuals, consistent with the documented tilt of NAVD88, will be addressed in future regional analyses.