E L E V A T I O N & D E P R E S S I O N

Angles of elevation or inclination are angles above the horizontal, like looking up from ground level toward the top of a flagpole. If the object is below you, the angle of depression is the angle your eyes look down.

Angles of depression or declination are angles below the horizontal, like looking down from your window to the base of the building in the next lot. 
















Whenever you have one of these angles, you should immediately start picturing how a right triangle will fit into the description.

Angles of elevation and depression are measured from the horizontal. It is common mistake not to measure the angle of depression from the horizontal.

Using the angle of depression or elevation to an object, and knowing how far away the object is, enables us to find the height of the object using trigonometry.

The advantage of doing this is that it is very difficult to measure the height of a mountain or the depth of a canyon directly; it is much easier to measure how far away it is (horizontal distance) and to measure the angle of elevation or depression.

Suppose that we want to find the height of this tree. We mark point A and measure how far it is from the base of the tree and then we measure the angle of elevation from A to the top of the tree.















Now,






we have measured x and θ, so we can calculate tanθ and thus we can find h, which is the height of the tree.

-k. v.