Quasi-geoid modelling using a fixed GBVP solution based on Brovar series in the Colorado experiment area

The solutions contributed to the Colorado 1 cm Geoid Experiment (CE) represent the state-of-the-art in precise high-resolution geoid and quasi-geoid modeling. They can be compared with other solutions, strategies, and procedures for determining regional models, including the implementation of the International Height Reference Frame (IHRF). We calculated a quasi-geoid model in the CE area using the 'simple' fixed Geodetic Boundary Value Problem (GBVP) solution based on the Brovar series and Hotine’s integral. This was solved using an efficient algorithm of numerical integration. The quasi-geoid model was calculated using data provided by the National Geodetic Survey (NGS) and in the Remove-Compute-Restore (RCR) fashion. Different tests were performed to determine the optimal configuration for the modeling. The optimal configuration was found employing a cap size of 1°, a modification degree of 719, and a transition degree/order ( d / o ) of 719. The model was statistically validated using Geoid Slope Validation Survey 2017 (GSVS17) GPS/leveling data and 12 contributing quasi-geoid models to the CE. The Root Mean Square (RMS) of the height anomaly differences between the computed quasi-geoid model and the GSVS17 data is 2.7 cm. When compared to the mean of the 12 quasi-geoid models, the RMS value is 2 cm. These results demonstrate that the proposed solution can be applied in the context of implementing the IHRF in other regions of the globe. It is worth noting that the methodology used here for the fixed GBVP solution differs from other fixed solutions contributed to the CE. Thus, this can be proposed as an additional contribution to the CE.