1, convex low is high, convex high is low. In contour lines, the higher the contour line indicates, the ridge, and the lower the contour line indicates, the ditch or valley. This rule applies to all contours.

2. If it is a contour line, if the height of the bulge is low, it means that the contour line bulges to a high value, and the low altitude here is the valley line (circle 2 below); The convex low is high, indicating that the contour line protrudes to the low value, and the altitude here is high, which is the ridge line (the circle below 1).

The second question:

The circle 1 in the above figure is the ridge; Circle 2 is a valley; Circle 3 is a depression or basin; Circle 4 is the peak (the contour line is closed and the middle is higher than the surrounding).