引用本文: 程璐, 郭庆胜, 费立凡, 魏智威. 利用点重要性序列的等高线间接综合[J]. 武汉大学学报 ( 信息科学版), 2024, 49(5): 856-867.
CHENG Lu, GUO Qingsheng, FEI Lifan, WEI Zhiwei. Indirect Generalization of Contours Using Importance Sequence of All Points[J]. Geomatics and Information Science of Wuhan University, 2024, 49(5): 856-867.
 Citation: CHENG Lu, GUO Qingsheng, FEI Lifan, WEI Zhiwei. Indirect Generalization of Contours Using Importance Sequence of All Points[J]. Geomatics and Information Science of Wuhan University, 2024, 49(5): 856-867.

Indirect Generalization of Contours Using Importance Sequence of All Points

• 摘要: 在等高线综合方法中,基于三维（3D） Douglas-Peucker（3DDP）算法的等高线间接综合具有良好的应用前景。3DDP算法是通过设置阈值达到删除地表次要点、保留主要点的目的,然而这种通过阈值更新的方式来获得目标综合尺度所需保留的点集,影响了等高线间接综合的效率,且未考虑点被选取时的语义信息。因此对3DDP算法进行修改,并将基于“最佳位置”收敛法提取的结构化地形特征线作为综合约束,提出一种利用点重要性序列的等高线间接综合方法,即在不删除任何点的情况下,根据点的几何与语义权重计算其重要性值,形成包含所有点的重要性值从大到小排列的一个点重要性序列,并从该点重要性序列中确定目标综合尺度所需保留的点集,从而实现等高线间接综合。实验表明,所提方法不仅能够提高等高线间接综合的效率,而且还能有效地防止等高线拓扑关系的变异。

Abstract:
Objectives In the generalization method of contours, the indirect generalization of contours based on three dimension (3D) Douglas-Peucker (3DDP) algorithm has a good application prospect. This method achieves the purpose of deleting the sub-points of the surface and reserving the main points by setting thresholds, but this threshold updating method affects the efficiency of indirect generalization of contours, and there is no consideration of the semantic characteristics of surface points in selection.
Methods Aiming at above problems, we presented an indirect generalization method for contours using the importance sequence of all points, and topographic feature lines considering terrain slopes extracted by an optimal position convergence method were taken as constraints of generalization. First, data was converted into 3D discrete points and sorted. Second, no points were deleted, and the importance of geometric weight and semantic weight of all discrete points was calculated to form an importance sequence which ordered all points from the largest to the smallest important values. Finally, according to the generalization target scale, the reserved points in the importance sequence were determined to achieve the indirection of contours.
Results Experimental results show that before the point selection method is improved, it takes about 18 minutes to select points by setting thresholds every time, which affects the generalization efficiency. However, the proposed method only takes about 25 minutes to queue all points by their importance values. Besides, by adding semantic information, the topological variation of generalized contours is reduced.
Conclusions The proposed method can not only improve the efficiency for the indirect generalization of contours, but also effectively prevent the topological variation of contours.

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