曲面和地形面 Curved and topographic surfaces

一、曲面 curved surface

      在标高投影中，用一系列高差相等的水平面与曲面相交，得到一系列交线 —— 即等高线，画出这些等高线的标高投影就得到曲面的标高投影。

      In elevation projection, cross a curved surface with a series of horizontal planes with the same elevation difference, and get a series of intersecting lines —— that is, contour lines. Draw the elevation projection of these contour lines to get the elevation projection of the curved surface.

正圆锥面 Right Circular Conical Surface

      正圆锥面等高线的特性：等高线都是同心圆；等高线高差相等时，其水平间距（即半径差）也相等；锥面坡度越陡，等高线越密；坡度越缓，等高线越稀；当圆锥面正立时，等高线越靠近圆心，标高数值越大；当圆锥面倒立时则相反。见图10-11。

      Characteristics of contour of conical plane: contour lines are concentric circles; When the height difference of contour lines is equal, their horizontal spacing (i.e., radius difference) is also equal. The steeper the taper slope, the denser the contour line. The slower the slope, the thinner the contour line; When the conical surface is upright, the closer the contour line is to the center of the circle, the higher the elevation value is. The opposite is true when conical surfaces stand upside down.

图10-11  正圆锥面等高线

      正圆锥面的坡度线：正圆锥面的素线就是锥面上的坡度线，所有素线的坡度都是相等的；圆锥面的示坡线均应通过锥顶。见图10-12。

      Slope line of normal conical plane: the prime line of normal conical plane is the slope line on the cone. All the prime lines have the same slope. The slope line of the conical plane should pass through the top of the cone.

图10-12  正圆锥面坡度线

图10-13  正圆锥面的应用实例 —— 河渠的转弯坡面

二、地形断面图 Topographic section

      用铅垂面剖切地形面所得到的断面形状称为地形断面图。见图10-14。

      The shape of topographic section is known as topographic section.

10-14  地形断面图