Estimación de un modelo micro-cuasigeoidal mediante el modelamiento del campo de gravedad local para la incorporación de la primera estación de Colombia en el IHRF

Abstract

In this document, the refinement of the regional gravity field is developed using spherical radial basis functions and a combined extended Gauss–Markov model, with the objective of determining a regional quasigeoid model of high accuracy and spectral richness. For this purpose, a mixture of gravity measurements from different techniques is generated in order to capture and model different frequencies of the signal originating from the gravity field. Likewise, a regularization of the system of equations is carried out through the estimation of the variance components (VCE, for its acronym in English) and, subsequently, the estimation of the Tikhonov regularization parameter λ using the L-curve method. In particular, for the representation of long wavelengths, the global geopotential model XGM2019 is used, whereas short to very short wavelengths are represented by a spherical harmonic combination of the Earth2014 and ERTM2160 models. In parallel, the consistency of the model is validated by means of GNSS/Leveling data, considering this data set as independent. The materialization of the International Height Reference System (IHRS, for its acronym in English) requires a reference geopotential surface that conforms to high-resolution quasigeoid modeling; consequently, the QgeoidMEDE2025 model computed in the present project provides a surface that meets the aforementioned specification and offers a solution for computing the geopotential number C(IHRF) associated with the International Height Reference Frame (IHRF, for its acronym in English) at the permanent monitoring station MEDE, which is part of the SIRGAS-CON geodetic reference frame as well as being one of the IHRF stations. In this order of ideas, the solution provided by the surface computed in this project is compared with the solutions of the continental SAM model (quasigeoid for South America) and the national QgeoidCOL2023 model. In this way, the work is fundamental for addressing the request of SIRGAS Working Group 3 (GT-III), by having three different solutions for the IHRF stations and, furthermore, for showing, in an approximation, that the different quasigeoid modeling configurations have direct implications for the computation of the geopotential numbers for the IHRF, C(IHRF).