When the line of sight is above the horizontal line, the angle between the line of sight and the horizontal line in the vertical plane where the line of sight is located is called elevation angle.
I guess it's not that you don't know the definition. Only in the application of mathematics, you don't have abstract thinking, or you don't feel very good. It is suggested to find a building, a freshman. From top to bottom, the angle formed by your eyes and the ground is the depression angle. Isn't there a word overlooking in Chinese? You're downstairs on the runway. When you look from the bottom up, the angle formed by the ground along your eyes is the elevation angle, which means looking up in Chinese. Have you ever seen a War of Resistance against Japanese Aggression movie? When the plane dives downward, it is necessary to use the depression angle. Look up at the ground observation plane or shoot the plane with elevation angle. To know that words cannot be explained, the key is to have abstract thinking, especially mathematics, otherwise geometry will be more difficult to learn in the future.