We often need to calculate the area of regular or irregular shapes to help estimate how much fertiliser or chemical needs to be applied to a section of turf.
Regular shapes
The area of a regular shape can be calculated using the formula:
area = length x width
For example, to calculate the area of a tennis court and its surrounds, use the following formula:
area = length (L) x width (w)
= 30 m x 20 m
= 600 square metres
Triangular shapes use a different formula:
Area of a triangle = half the base x height
For example, to establish the area of the throwing arc of a discus enclosure:
area = ½ base (b) x height (h)
= ½ 50 m x 80 m
= 25 x 80
= 2000 square metres
Circular shapes use a different formula:
Area of a circle = r2
For example, to work out the area of a circular golf green
Area = r2
= 3.14 x 15 x 15
= 706.5 square metres
Irregular shapes
Sometimes it's necessary to estimate volumes of irregular areas such as kidney shaped garden beds or hourglass greens.
The key to measuring the area of curved shapes is to calculate an average radius and then apply the formula for circular shapes.
For example, to calculate the area of a kidney shaped green firstly calculate an average radius. This is done by measuring from a central point (not necessarily the exact centre) of the green to the edge of the green at ten degree intervals.
Click on the 'Play' button below to see how this is done.
Total all the measurements and then divide by the number of measurements to give an average radius. This can then be used in the standard formula for the area of a circle:
Area = r2
If the average radius was 15 metres then:
= 3.14 x 15 x 15
= 706.5 square metres
Some irregular shapes may actually have a combination of regular shapes, which you can use to work out the area
For example, a golf practice tee with bell shaped ends actually looks as if it is an irregular shape. However, it can easily be divided into a number of regular shapes – a rectangle and two half circles.
Therefore the formulas for the area of a rectangle and area of a circle can be used to calculate the area.
Area of a rectangle = length x width
= 40 x 20
= 800 square metres
Area of a circle = r2
= 3.14 x 10 x 10
= 314 square metres
As this area is for a full circle, each half circle will have an area of 157 square metres.
Therefore the total area of the practice tee = area of rectangle + area of circle
r2
r2