中文摘要：

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。

英文摘要：

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 .