【作者】 陈明春；

【导师】 江崇礼；

【作者基本信息】 大连理工大学 ， 控制理论与控制工程， 2008， 硕士

【摘要】 地理信息的提取和识别是地理信息系统(GIS)、全球定位系统(GPS)发展的基础和迫切需要。栅格地图矢量化已经成为获取地理信息的主要途径之一。本文在研究、分析目前具有代表性的扫描图像矢量化方法的基础上,针对栅格图像的特点,用Visual C++6.0编程语言实现了一个地图矢量化系统RasToVec。本文采用目前比较流行的基于细化的矢量化方法作为整体设计思想。首先根据地图不同地理对象灰度级不同的特点,将地图中的文字等标注从地图中分离,然后用最大类间方差阈值分割法将地图进行二值化。对二值化后的地图运用数学形态学进行噪声滤除和轮廓提取。然后对图像进行细化,细化时采用一种基于标记的保留节点域的细化方法,该方法避免了传统细化方法中节点变形从而改变图形拓扑结构的问题。对细化后的图像矢量化时,本文根据地图的整体拓扑特征,先将地图中的节点域和连通弧段提取出来,然后利用遗传算法将连通弧段进行矢量化得到连通矢量弧段,根据最长延伸原则合并矢量弧段,确定节点,并得到最终的矢量段。矢量化算法除了采用遗传算法外,还采用了道格拉斯算法,最后对这两种算法的效果和效率进行了比较。在细化及连通弧段编码过程中都采用边处理边擦除象素的方法,有效避免象素的重复处理,降低图像的复杂度,并提高了矢量化的速度。目前矢量化研究大多是在工程图领域进行的,本文提出的算法是根据地理信息系统的要求设计的,在保持地图拓扑结构及矢量化准确性方面取得很好的效果,并实现了与GIS软件MapInfo的接口,在地理信息系统领域有一定的理论意义和应用价值。更多还原

【Abstract】 Extraction and recognition of the geography information is the basis of geographic information system(GIS) and global position system(GPS). The vectorization of grip maps has become one of the main methods of getting digital information. After studying some typical map vectorization methods, the author realizes a map vectorization software, RasToVec, with Visual C++ programming language to recognize and capture the geographic elements in the grid maps.The current prevalent vectorization method based on thinning algorithm is adopted in the paper. Firstly, words labels in the scanned gray map are separated from the map as its gray rank is different from the other objects’ in the map. Then the gray map is transformed into binary map by maximal threshold variance method. Noises in the binary map are filtered and geographic elements’ edges are extracted by morphology. In the process of thinning the image, a new thinning method based on labeling is put forward. Compared with the traditional thinning algorithm, this method avoids the node distortion and map topology changing.In the process of vectorization, the node area and connected segment are abstracted according to the whole topology of map. The connected segment is transformed into its vector form by genetic algorithm(GA). The longest expended principle is used to combine the vector segment, and then the nodes are ensured and the last vector list is got. Besides GA, Douglas-poiker method is used in the process of vectorization and the comparison of these two methods in efficiency and precision is presented in the end. The erasing pixels process after thinning and segments coding avoids re-recognition and complexity, so the speed is improved.At present the research on vectorization is mainly among the engineering images. The method proposed in the paper satisfies the demand of GIS and realizes the interface with software MapInfo. The experimental results show that this method can reestablish the map’s topology and get a good performance in precision and efficiency. This paper presents certain significance and application value in the field of GIS.更多还原