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MEASURING YOUR GARDEN: TRIANGULATION
Suppose the example on the earlier page had a plot that wasn't square. The easiest way to take measurements from a plot like this is to triangulate. This involves taking two measurements from a fixed point that is square onto the page - usually the house - to the point that you wish to plot. In this case, we will use points A and B as shown in figure 1 for our fixed points.
Take running measurements of the house only and draw it onto your scaled plan. Then take two horizontal measurements from a point on the house to the boundary. Try to come straight out, at right angles to the house. These will give you points C and D. Scale those measurements onto your plan and mark with a cross. (Figure 2).
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Now, we need to find points E and F and, to do this, we need to triangulate. Take a measurement from point A to point E and another from point B to point E. (Figure 3)
On your scaled plan, draw (in pencil) two lines, one from point A and one from point B. These lines can go in any direction as long as they are the same measurement as the one you have taken. For example on a 1:100 scaled drawing, the line from point A will be 7cm.
Now, with a compass draw a circle (in pencil) which has, as its centre, point A and its circumference touching the end of the line you have drawn. In other words, you draw a circle, centre point A and radius 7cm. Do the same for point B.
You will see that both of the circles cross at a specific point. (Figure 4) This is your point E and you can mark this on your diagram with an X and remove the circles and lines you have just drawn. Repeat the procedure for point F.
Now you can join up the crosses to complete your boundary. (Figure 5)
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You can now use triangulation to mark the position of permanent features in your garden such as trees. But, suppose you have a feature you want to keep that is curved. In that case, you need to take OFFSETS.