# Angles of elevation and depression

This chapter explores angles of elevation and depression. It covers working with angles of elevation and depression and using scale drawing and trigonometry to calculate heights of tall objects. No prior knowledge is required for this chapter.
Engineers use trigonometry to work out very high heights such as a tree and tall buildings. The following image shows an old chimney. Engineers need to work out how tall it is;
The engineers stand 100m from the chimney. They measure the angle of elevation shown below using a theodolite.
They find out that the angle of elevation is 32°. Suppose they wanted to work out the height.
One way to work out the height of the chimney is to so a scale drawing. We could use a scale of 1cm for 10m. First we draw a line 10cm long.
Then we draw an angle of 32 ° as shown below.
Then we join the height.
Finally we measured the height using a ruler. You’ll find that it is 6.3cm.
6.3cm represents 63metres in the scaling above. We have found out that the chimney is 63m high.