1.5 Basic Linear Survey

Question 1

Llnear site survey is carried out to…

Answer 1

A linear site survey is carried out to produce an accurate to scale plan, produced before a design can be developed.
It will accurately plot all features within a garden.

Question 2

Equipment used for site survey

Answer 2

• pegs
• 100m builders string line
• 30m surveyors tape, 10m retractable rule
• Clipboard, paper, pencils, rubber, scale rule

Question 3

To record a linear survey you will begin by…

Answer 3

• establishing a baseline
• measuring features from the baseline by either:
• Offests measured at 90 degrees
  or
• Triangulation

Question 4

Establishing a baseline…

The baseline is a straight line between to known points and it is the point from which all other features will be recorded. It is important to be accurate measuring the baseline as this will affect all other measurements of the Survey.

Answer 4

A flat wall of the main house on site can be used as the baseline, or a line that may be accurately measured a specified distance from it can be used.

eg. Measure 3m (at right angles) from the near corner of the house, label this point A. Then measure 3m (at right angles) from the far corner of the house and label this point B. Suspend a Builders String Line along the two points using pegs or bamboo canes. A surveyors tape suspended along the baseline will also be useful.

Baseline must be measured from a point that is permanent and fixed so a repeatable measurement could be produced in the future.

Make sure the baseline is straight, taut and parallel to the house or points measured from.

Question 5

Offsets

are measurements taken at right angles from the baseline. A method of accurately measuring features that lie away from a baseline for transfer to scale plan.

Answer 5

Take a running measurement along the baseline to where the garden feature is perpendicular. Carefully record this measurement.
At right angles from the baseline record the distance to the garden feature.

Make detailed records of the specific item. Then the running measurement along the baseline from point A, and also the measurement from the baseline perpendicular to the feature.

90degrees may be gained by using a builders square, using the 3,4,5 method or the perpendicular lines method.

Question 6

Triangulation

using the datum points on a baseline to measure distances to the feature. It is used alongside Offsets to measure a site, using which ever method is more accurate and easier.

Answer 6

Measure accurately from the Baseline datum point A, to the specific garden feature (can be labelled as C). Record the measurement.

Measure accurately from the Baseline datum point B to the feature C. Record the measurement accurately.

These three measurements, A-B, A-C, B-C can be used to plot the feature on the scale plan.

Triangulation may also be used, to measure to the boundary corners. Then along the fence line to complete the perimeter measurements.