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Ground tracking
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PERGOLAS and GAZEBOS do-it-yourself
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Ground tracking

Friday 15 June 2012,

In this first step, you perform the identification on the ground

The reference line

The reference line serves as a benchmark for the duration of the work. It is the basis to determine all other measures.

One might be tempted to take as a reference the facade housing against which the pergola will be contiguous. But a façade is rarely well straight. May be dips and bumps. Then it could get errors in positioning depending on the location of the facade from which we take our measure.

It will draw a new reference to a few inches of the front line. This falls well, this pergola model must not be pasted against the facade but detached from 10 cm (edge of the beam-carrier). It adds the width of the beam-carrier B and it gets the distance from the wall to the poles or X 1 = 13.8 cm. It is at this distance we trace our line of reference. And the Poles against the facade are aligned on the line.

To draw the line, took two measures of X 1 = 13.8 cm. from the edge of the façade. The two points are remote as possible.

1 - Mark on the left
On the left side of the façade, plotted a line of reference to X 1 = cm to the edge of the façade.
2 - Mark right
then it is the same right.
3 - Tracade of the reference line
Between the two lines mark drawn previously, we trace the reference line. On this diagram uses a rule of Mâcon. But can also be used a powder cord which allows to make beautiful straight on great lengths.

1St line perpendicular

This line forms the right edge of the pergola. It is important to be precise on the path and achieve a perfect perpendicular. Can be used a square of macon has the advantage of simplicity but is not very precise. However, the method "3-4-5", a little more technical to get good accuracy.

1 - Identification of the width L1
On the reference line, plotted two L1 =350cm spaced guides. This represents the left and right edges of the pergola.
2 - Trace of the perpendicular
  • According to the method "3-4-5" (see below).
  • or with a square of Mâcon.

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The method "3-4-5" :

According to Pythagoras, C² = A² + B². Where C is the length of the diagonal, A and B two perpendicular lines.
Or, he is as 5² = 3² + 4² (25 = 16 + 9).
This means that if a diagonal of 5 m connecting two lines 3 and 4 m, then these two lines are perpendicular.


  • on first spotted a line of 3 m on the reference line (if your rule of Mâcon is 4 m) or 4 m (if your rule is 3 m).
  • Then it positions macon rule roughly perpendicular to the 1st line.
  • With a metre to Ribbon, or at best with another rule of 5 m macon, it positions the diagonal to the two lines.
  • It adjusts the rule of Mâcon and the diagonal until it measures 4 m and 5 m coincide. This requires a bit of successive adjustment but through trial and error while finesse, it gets a good accuracy.

2Nd perpendicular

1 Benchmark P1
On the 1st perpendicular line, locate the P1 distance from the reference line.
2 - Benchmark P1 and L1 left

Identify the distance L1 on a 1 meter tape from the 1st perpendicular. At the same time, identify P1 from the reference line on a 2 metre Ribbon. Make coincide the two-metre Ribbon. At the junction, draw a cross.

If you don’t have that one meter, locate successively L1 and P1 by drawing a small circle arc, by pivot on the meter casing.

3 - Draw 2 perpendicular
Using the rule of Mâcon, which part of the marker on the reference line, and that aligns the mark cross as it drew 2, plotted the second perpendicular line.

The last row

1 - Draw the last line
The last line is drawn after the previously traced benchmarks. Macon rule or the cord to powder can be used.
2 - This is what you should get
3 - Audit

Check the diagonals one way then the other. The value of the diagonal should be 430.1 cm.

If the difference is greater than 5 mm, try again and check of the beginning.

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