Impact of residual terrain modeling (RTM) approaches on local quasigeoid determination in Argentina

The determination of the short-wavelength components of the Earth’s gravity field is crucial for regional quasigeoid modeling within the remove-compute-restore (RCR) framework. Residual terrain modeling (RTM) estimates these high-frequency signals by calculating the gravitational effects of masses between the topography/bathymetry and a smoother reference, referred to as the RTM surface. This study evaluates two RTM approaches for quasigeoid modeling in five regions surrounding the Argentinean stations of the International Height Reference Frame (IHRF). The first approach, named classical (CL), is based on numerical integration with an RTM surface derived from a moving-average operator applied to the SRTM v4.1 and SRTM15+ v2.5.5 models. The second approach, denoted spectral (SP), employs a spherical harmonic representation of the topographic gravity field based on dV_ELL_Earth 2014 and numerically-integrated RTM effects from ERTM2160. Both approaches are used along with the XGM2019e global geopotential model (GGM) at four truncation degrees. Height anomalies are computed from residual gravity anomalies by employing the Molodensky integral with a Wong-Gore kernel modification. The results show that the SP approach yields residual gravity anomalies up to 75% smoother than the CL approach and reduces the GGM truncation ringing effects. The models' agreement with GNSS/leveling data shows an improvement of up to 0.04 m between the lowest and highest truncation degrees. The highest estimated precisions range from 0.165 m in regions with more complex topography down to 0.052 m in flat areas. Overall, the SP approach has a comparable or slightly higher performance than the CL approach.