Abstract: In order to further improve the loading efficiency of electronic nautical charts based on WebGIS technology in the front-end, the dividing method of nautical chart vector tiles was thoroughly studied. On the basis of considering the spatial distribution consistency of elements, a combined grid division method of nautical chart tiles was proposed. The vector tile data threshold was introduced into the quadtree division process to transform it into an unbalanced quadtree, which was the first stage of tile division. After the tiles were divided to the point where the maximum amount of data for a single tile was less than the data threshold, the second stage of tile division was carried out by the binary tree with the fusion of the variation coefficient. The data and experiment results of vector tiles generated by the combined grid method, the original uniform grid method and the improved uniform grid method were compared. The research indicates that in the range of tile level 3~9, the vector tiles generated by the combined grid method based on element consistency have smaller standard deviation in the same level compared with the two uniform grid methods, and the distribution of the vector elements is more balanced on the tiles, and the vector tiles generated by the combined grid method have shorter loading time in the same view window range.

摘要： 为进一步提升基于WebGIS技术的电子海图在前端的加载效率，对海图矢量瓦片的划分方法进行深入研究。在考虑要素空间分布稠度的基础上，提出一种海图瓦片的组合格网划分方法。在四叉树划分过程中引入矢量瓦片数据阈值将其改造成非平衡四叉树，作为瓦片划分的第1阶段，在瓦片划分至单瓦片最大数据量小于数据阈值后，通过融合变异系数的二叉树对瓦片进行第2阶段的划分。将组合格网法、原始均匀格网法和改进均匀格网法生成的矢量瓦片数据与试验结果进行对比。研究结果表明，在瓦片第3~第9层级范围内，相对于2种均匀格网法，基于要素稠度的组合格网法生成的矢量瓦片在同一层级的标准差更小，矢量要素在瓦片上的分布更加均衡，在同一视窗范围内，组合格网法生成的瓦片加载时间更短。