[S-GD01] Geodetic Advances in Crustal Dynamics and Environmental Change for Taiwan and Neighboring Regions

[SGD01-11] Coastal GNSS-IR Altimetry for Determination of Vertical and Depth Datums: A Case Study in Taiwan

*Chi-Ming Lee¹, Chung-Yen Kuo¹, Wen-Hau Lan², He-Chin Chen³, Ning-Kai Kang³, C.K. Shum⁴ (1.National Cheng Kung University, 2.National Kaohsiung University of Science and Technology, 3.National Land Surveying and Mapping Center, Ministry of the Interior, 4.The Ohio State University)

Keywords:Vertical datum, Depth datum, GNSS-IR, Tide gauge, Satellite Altimetry

The establishment of precise and reliable vertical and depth datums is crucial for various applications, including maritime navigation, coastal engineering, and sea level monitoring. Traditionally, these datums are determined using long-term (> 18.61 years) tide gauge observations, with vertical datum referenced to mean sea level (MSL) and depth (chart) datum based on the lowest astronomical tide (LAT), respectively. This study investigates the utilization of a GNSS station at Kaohsiung Harbor, Taiwan, to complement coastal GNSS Interferometric Reflectometry (GNSS-IR) altimetry for datum determination. By incorporating GNSS positioning results, the ellipsoidal heights of the sea surface can also be calculated, providing the absolute mean sea surface relative to the ellipsoid. The GNSS-IR retrievals are evaluated through comparisons with co-located tide gauge measurements, assessing the accuracy and reliability of the GNSS-IR derived MSL, LAT, and other reference surfaces used in depth datums. In addition, gridded and along-track satellite altimetry is also utilized for sea level changes validation. This study aims to explore the feasibility of GNSS-IR technology as a viable alternative or complementary to conventional tide gauge network for defining vertical and depth datums, potentially improving coastal geodetic infrastructure and sea level observation systems.