一种基于云图绘制的等高线生成方法

A Method of Generating Contour Based on Nephogram

针对不规则三角网法在绘制等高线时仅在三边提取等高线控制点而出现控制点不足,从而导致绘制线形差的问题,提出了一种基于数据点高程云图对整个云图区域提取控制点的等高线绘制方法,首先利用OpenGL图形库提供的丰富的图形程序接口,根据距离最短和角度最大原理,建立数据点不规则三角网(TIN)模型;然后将数据点高程和颜色RGB值一一对应,实现数据点高程云图的生成;最后遍历数据点高程云图,按高程对应的颜色值提取等高线控制点,连接具有同一颜色值的控制点完成等高线图的绘制。实例应用结果表明,运用该法绘制等高线扩大了控制点的搜索范围,增加了等高线控制点的数量,使绘制的等高线图的线性较好,且与实际地形较符合。

Aiming at the problem that it has not enough control points and bad lineshape when using irregular trian- gulation method to draw contour line, this paper proposes a method that extracts the contour control points from the whole nephogram zone instead of the three edges of irregular triangulation method. By using the rich graphics program in- terfaces provided by OpenGL graphics library and according to two principles of shortest distance between two points and maximum angle among three points, the triangular irregular network （TIN） of data points is established and the nepho- gram of data points are generated by one-to-one correspondence between data-points elevation and color RGB values. And then, the control points of contour line are extracted with the same color value by traversing the elevation nephogram of data points. Finally, the contour plot is generated by connecting the control points with the same color. An example shows that this method for plotting contour line expands the search scope of control points and increases the number of contour control points. So, the line-type of the contour is better and it is suitable for the actual terrain.