Core Viewpoint - The article discusses the establishment of China's first tidal observation station at Kanmen, which marked a significant step in creating a national elevation benchmark, allowing China to independently measure sea levels and break free from foreign control over tidal observations [4][48]. Group 1: Historical Context - China has the largest elevation difference in the world, with a height difference of 9003 meters between Mount Everest and the Turpan Basin [5]. - Before 1934, China lacked a unified elevation benchmark, leading to confusion and discrepancies in measurements across different regions [20][26]. - The establishment of a standardized elevation point was crucial for efficient governance and infrastructure development, as seen in historical examples like the unification of measurement standards by Qin Shi Huang [21][22]. Group 2: Establishment of Kanmen Tidal Station - The Kanmen tidal station was established in 1930 after extensive research and site selection by Cao Mu, a prominent figure in Chinese surveying [29][30]. - The location was chosen for its ideal conditions, being away from major river mouths and coastal disturbances, ensuring accurate tidal measurements [31][34]. - The station faced initial challenges, including structural issues due to erosion, which were later resolved with upgrades to the observation well [39][40]. Group 3: Impact and Legacy - The Kanmen station provided the first independently calculated elevation benchmark for China, ending reliance on foreign measurement standards [45][48]. - The elevation benchmark established at Kanmen was critical for the development of a unified national elevation system in 1956 [50]. - The station has continued to evolve, contributing to marine observation and disaster response efforts, demonstrating its ongoing relevance in modern times [56][58].