There are plenty more beach fieldwork options to come, but first you need to make yourself another piece of equipment – a quadrat.

To make one of these you need something to make the outside frame and then string to divide the central area into smaller squares.  You also need a tape measure to help you get everything in the right place.

For the frame I used garden canes, but lengths of wood would work too and would probably be more robust.  You need to cut 4 lengths of about 60 cm.  The inside edge of the frame will be 50 cm x 50 cm, but you need the extra length to fix them together.

Use string to lash the frame together at the 4 corners.  (Lengths of wood could be screwed together.)

Make sure the internal area of the square is exactly 50 cm by 50 cm.

You are going to divide the frame every 10 cm.  Mark the edge with permanent marker so that you know where to fix the strings, and so that you can see where they should be, if they slip out of position.  There should be marks at 10, 20, 30 and 40 cm on each side.

Now tie strings across.  Go first one way…

…and then the other way, twisting around each of the first set as you go.

Check the squares are still square (10 cm by 10 cm) and adjust if necessary.

And there you have it…

…a very useful piece of kit.

Here’s one way to use it.

As you can see my patio needs weeding!  We can use the quadrat to help us estimate the percentage of my patio that is covered in weeds.

Throw the quadrat down.  Yes, don’t place it, since that would be you choosing the results.

The quadrat has 25 small squares so each of them represents 4%.  Give each square a score:

• Square is all weeds = 4
• Square is ¾ weeds = 3
• Square is ½ weeds = 2
• Square is ¼ weeds = 1
• Square has no weeds = 0

Add them up and you can see that 45% of my patio is covered in weeds.

I’m off to do some gardening, but I’ll be back next week to tell you how to use your quadrat at the beach.