基于规则格网DEM的等高线绘制与优化

Drawing and Optimization of Contour Lines Based on Grid DEM

针对高程格网数据的海量性,以增强数据可读性和提高绘图效率为目的,对传统绘制等高线过程进行优化。实验将绘制等高线图分为3大步:数据预处理、建立高度索引、根据索引绘图。首先,采集和简单处理原始DEM(数字高程模型)数据,提取数据中与绘图相关的核心信息,如整幅地图中左上端点和右下端点的经纬度,最大高度和最小高度等。其次,在数据预处理后的基础上,再次解剖数据,即通过等值点判断、等值点线性内插和等值点追踪生成可读性强的高度索引文件。最后,根据建立好的高度索引数据来构建数据结构,合理储存信息,利于计算机快速绘制等高线图。

According to the large amount of DEM data , in order to enhance the data readability and improve drawing efficiency , we optimized the traditional process of drawing the contour lines .The entire process was divided into three operations：Data pre-processing , building height index , mapping in accordance with the index .First of all , by collecting and simply processing the o-riginal DEM （digital elevation model） data, we extracted the key information related to mapping in the data , such as the latitude, longitude, maximum height and minimum height of the endpoints left-up and right-down in the whole map.Secondly, based on data preprocessing , we analyzed the data again through the equivalent point judging , the equivalent point linear interpolation and the equivalent point tracking to establish the strongly readable index files of height .At last, according to the height index data , the data structure was constructed to reasonably store data , so it could help the computer fast drawing contour map .