Method and principle of making contour lines

1. Definition and principle of contour line: contour line refers to a closed curve formed by connecting adjacent equal elevation points on topographic map. Connect the points with the same altitude on the ground into a closed curve, project it vertically on the horizontal plane, and draw it on the map in proportion to get the contour line. The contour line can also be regarded as the intersection line between the horizontal plane with different heights and the actual ground, so the contour line is a closed curve. The number marked on the contour line is the height of the contour line.

Second, the production method of contour lines:

Firstly, connect geological lines, that is, valley line and ridge line; Connect the upper and lower adjacent points, calculate the passing position of the instrument curve by interpolation method, get the passing position of the instrument curve between all points in the same way, and connect all the passing points to form the instrument curve; Insert five first curves evenly by interpolation, and pay attention to the relationship with the actual elevation to avoid the contradiction between lines and points. Pay attention to the intersection of contour lines and geological lines. At the ridge, the contour line protrudes outward, and at the valley, it protrudes upstream. The basic principle of computer drawing is the same, but it is more convenient. ?

Third, contour production steps:

(1) feature points refer to the vertex, saddle point, slope transformation point, slope toe transformation point, intersection point between the foot of the mountain and the flat ground, etc. The plane position of feature points on the map is determined by polar coordinate method or intersection method, which is represented by small points, and the elevation is marked next to the small points.

(2) After determining the characteristic points of the landform, the geodetic line should be connected first, and the contour line cannot be drawn immediately. Usually, the solid line is connected with the ridge line and the dotted line is connected with the valley line, so you must draw while measuring. With the determination of the breakpoint, the earth line must be connected at any time.

(3) After the geological line connection is completed, the contour line of each whole meter elevation can be interpolated between two adjacent points with the same slope through points, and then the points with the same elevation can be connected according to the characteristics of the contour line, which is the contour line.