A Study on Methods for Determining the National Normal Height in Vietnam

The establishment of a national standard height system is essential for ensuring the consistency and accuracy of geodetic and surveying activities. In this study, 09 points first-class national benchmarks, selected for their superior stability, were utilized as reference points. A formula was subsequently proposed to determine the standard heights of 75 second-class national benchmarks. The benchmarks were measured using high-precision Global Navigation Satellite System (GNSS) techniques, with data processing conducted within the International Terrestrial Reference Frame (ITRF). The analysis revealed that, assuming an accuracy of ± 0.075 meters for GNSS-based height determination, 45 out of 75 second-class benchmarks (60%) exhibited deviations exceeding the ± 0.075-meter threshold, while 30 points (40%) remained within acceptable limits. These findings highlight the need for further refinement of the national quasigeoid model. It is anticipated that as Vietnam continues to enhance the precision of its quasigeoid model, the accuracy of national height determination will correspondingly improve, contributing to the development of a unified and reliable geodetic infrastructure.