关键词: 渐进式传输, WebGIS, 等级搜索树, 可缩放的矢量图形（SVG）

Abstract: In order to satisfy real-time publication requirements of GIS spatial data in marine oberservation system，a novel incremental storage model，based on thorough discussion of models for progressive transmission of vector spatial data，adopted an variant multi-way search tree named level search tree，is introduced.In the proposed method，a classic Douglas-Peucker （DP） algorithm and a new vector height classification algorithm are adopted to retrieve spatial data with diverse resolution and then the new level search tree is introduced as the incremental data buffer storage model.Finally，vector maps are created using SVG technique.The experiments in the end also demonstrates the applicability，feasibility and efficiency of this new model on embedded WebGIS platform，and it enhances its real-time ability while saving much bandwidth.

Key words: progressive transmission, WebGIS, level search tree, Scalable Vector Graphics（SVG）