How to read contour topographic map?

First of all, we should master the basic characteristics of isoline map.

(1) quantitative characteristics, look at the numerical contour, read the altitude of any point, compare the altitude of two points to convert the temperature difference, and calculate the actual distance on the ground with the horizontal distance between the two places.

(2) Geomorphological features: the surface presents various forms, and each geomorphological form has certain external features, which will be shown in different forms on the contour map. Look at the density of contour lines and you will know how steep the slope is. By observing the shape of contour lines, we can determine the types of landforms.

Second, we should master the basic knowledge of contour lines, which is the key to identify contour maps.

(1) All points on the same contour are equal in height, and the sea level is taken as zero meter. The height of two adjacent contour lines is the same.

(2) Vertical spacing diagram Consistent vertical spacing refers to the height difference between two adjacent contour lines. For example, the elevations of the three contour lines are 500m, 600m and 700m respectively, and the vertical spacing is100m.

③ Contour lines are closed curves. No matter how tortuous it is, it will eventually form a circle, but it is not necessarily closed on a picture.

(4) Two contour lines must not intersect because under normal circumstances, there will be no two heights in the same place. But on a vertical cliff, contour lines can overlap.

⑤ The density of contour lines reflects gentle slopes and steep slopes. Sparse contour lines indicate gentle slopes, dense ones indicate steep slopes, and evenly spaced ones indicate uniform slopes.

⑥ When the contour lines intersect the ridge line or valley line vertically, the contour lines on both sides of the ridge line are slightly parallel. When the contour line passes through the valley (valley line or catchment line), it bends upstream to form an inverted V-shape.

⑦ When the convex sides of two pairs of contour lines are symmetrical to each other, it is the saddle of the mountain, also called the pass of the mountain.

Today, the slope indicator line indicates the descending direction. The slope indicator line is a short line perpendicular to the contour line, always pointing to a lower height, sometimes called the descending line.

Pet-name ruby several special contour lines, 0 meter line represents sea level, that is, coastline; The 200-meter line separates the plain from the low mountain; 500 meters, 1000 meters shows low mountains or plateaus; 2000 meters and 3000 meters reflect Zhongshan and Plateau; 4000 meters embodies the characteristics of the Qinghai-Tibet Plateau and high mountains.