栅格地形图断裂等高线的自动重建

Auto-reconstructing Broken Contour Lines Extracted from Raster Topographic Maps

彩色栅格地形图分割提取的等高线图像中往往存在大量断裂,影响了等高线快速数字化采集.为了最大程度地实现图中所有断裂等高线正确匹配连接,提出一种断裂等高线自动连接重建方法.首先设计了多重递增回溯加权算术平均求断点方向角算法来提高断点方向角运算精度;然后设计了梯级最大约束角控制策略,从局部到全局逐级控制断点间匹配连接时的平缓程度,保留满足最大约束角条件的备选断点;最后采用欧氏距离和偏移角加权组合求断点匹配度算法确定最佳匹配断点;山脊、山谷等处折角过大的断点设计了抛物线形状断点方位码双向匹配算法进行匹配连接,图像边界区域断点沿前进方向自然延伸到图边.实验结果表明,该方法具备更高的正确率和完成率,稳定性和实用性好.

There often are various gaps on the extracted contour lines images after color raster topographic maps＇ segmentation, which affect digitalizing contour lines quickly and automatically. In order to realize broken contour lines＇ accurate matching and connection as many as possible, an efficient approach for broken contour lines＇ automatic reconstruction is proposed in this paper. Firstly, the algorithm of multiple incremental back-tracing and getting weighted average of endpoint＇s directional angle is designed for enhancing the precision of endpoint＇s directional angle; then max constraint angles control mechanism with multiple graded ranks is used to control transitional smoothing degree, and obtain the chosen endpoints satisfying the condition; lastly, the algorithm combining weighted Euclidean distance and offset angle between endpoints is put forward to determine the optimum matching endpoint. Besides, bidirectional matching algo-rithm based on parabola shape is supplemented to solve the remaining complicated and acute end points located in ridge and valley areas. The end points close to the map＇s edge are also prolonged in their respective line direction until reach the edge of map. The comparative experimental results indicate that the proposed approach holds higher accuracy and completeness, better stability and applicability.