1947年中国南海断续线精准划定的地形依据

基于1947年中国政府内政部印制的1:400万《南海诸岛位置图》,采用地理信息系统及数字化仿射变换精准测量出11段断续线的地理坐标,同时利用4.4万多个实测水深点数据建立南海海底三维地形模型,通过叠加分析获得了1947年南海断续线所在位置的海底地形特征。结果显示：断续线东长西短,间距东西大、南北小,其走向、形态与下伏地形特征相符合,主要分布在大陆坡和大陆架上;并基于断续线下伏海底地形分析,推断出当时断续线划定时可能遵循如下依据：① 在浅海盆地、海峡处采用“等距离中间线”原则进行划分;② 在具有明显地形变化处沿海槽坡麓或海槽槽沟中线进行划分;③ 在西南部陆坡陆架区,结合岸线走向及下伏地形特征进行划分。

Spatial demarcation principles of the Dotted Line in the South China Sea

The latitude/longitude coordinates of eleven dotted-line segments in The Location Map of the South China Sea Islands (Nanhai zhudao weizhi tu, in Chinese) of the scale 1:4,000,000, produced by the then-Chinese government in 1947, were determined by affine transformation in the geographic information system. Based on this map, a three-dimensional terrain model of the South China Sea was built and then the seafloor topographic characteristics were analyzed with the spatial overlay algorithm. Results show that the lengths and intervals of the dotted-line segments vary with their geographic locations, with larger lengths in the east and smaller lengths in the west. The range and shape of the dotted-line segments, mostly located on the continental slope and shelf, are parallel to the underlying topography. Three principles for demarcation of the dotted line are further summarized: (1) the principle of "equidistance midline" is adopted for the shallow sea basins and canyons; (2) in areas with dramatic reliefs, it follows the axis of troughs; (3) on the southwestern continental slope and shelf of the South China Sea, the shoreline and underlying topography control its distribution. These results could provide the Chinese government a scientific basis for the solution of disputes in the South China Sea.