Abstract
The global navigation satellite system (GNSS)-derived height determination technique is applied in the field of surveying owing to the broad use of GNSS and the development of precise local geoid models. In Korea, this technique was officially adopted in 2020 for public surveying, such as urban facility mapping; it is also treated as an efficient way to unify the vertical datum of the inland and island areas of Korea. Here, GNSS surveying was conducted on 19 stations located in Korea’s coastal regions and islands, and GNSS-derived elevations were determined. When each GNSS-derived elevation was compared with elevations from spirit leveling, all stations showed differences of less than 3 cm when GNSS surveying was conducted for 4 h/day over two days; they were smaller than 5 cm with 2 h of surveying. These differences meet the standards of GNSS-derived elevations in Korea. In addition, GNSS-derived elevations were compared with those obtained via sea-crossing leveling in two regions, showing differences smaller than 1 cm. Sea-crossing leveling takes longer than GNSS-derived height determination, and its accuracy can be significantly affected by various environments, such as sea fog. Thus, GNSS-derived height determination represents a practical and useful technique.
Highlights
The global navigation satellite system (GNSS) is one of the most commonly used techniques for determining the precise positions of various objects, including surveying control stations
To evaluate the precision of the GNSS-derived elevations in coastal and island areas, here, GNSS surveying was conducted on control stations with elevations determined by spirit leveling and comparisons were made between the two methods
When surveying is performed again, the elevation difference between stations should not exceed 15 mm S according to the Korean surveying guidelines [27]. This means that the results from seacrossing leveling and GNSS-derived height determination should coincide with a level of approximately 2.7 cm; in both cases, these techniques met this limit
Summary
The global navigation satellite system (GNSS) is one of the most commonly used techniques for determining the precise positions of various objects, including surveying control stations. Spirit leveling has been continuously used to determine (orthometric) height so as to coincide with the local vertical datum in each case and to ensure precision, despite the widespread use of GNSS in the field of surveying. In the case of Korea, control stations located inland were determined through spirit leveling by fixing the origin of the benchmark, which is connected to the Incheon mean sea level. GNSS-derived height determination is considered an efficient way to determine elevations of stations located in the coastal and island areas and connect the separated vertical datum, but its precision has not been evaluated clearly. To evaluate the precision of the GNSS-derived elevations in coastal and island areas, here, GNSS surveying was conducted on control stations with elevations determined by spirit leveling and comparisons were made between the two methods. The elevations of the control stations located in the two regions were determined by sea-crossing leveling and compared to elevations from GNSS-derived and spirit leveling to analyze the possibility of replacing sea-crossing leveling with GNSS-derived height determination
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