Describe how to carry out basic linear surveying techniques, including the use of tapes, offsets and triangulation.

How to carry out a linear survey using measuring tapes; including running measurements along a defined base line, offsets at 90 degrees and triangulation to specific points.

LINEAR SURVEY

Surveying from baseline / offset Start by roughly dissecting your garden as shown with the long pink line. Put a wooden peg into the ground at each end (in the case of a patio you will have to tie it to a chair or heavy object. It does not have to be parallel to anything but we are going to project off of this at right angles so take the easiest route possible.

Surveying from baseline / offset Now tie a small piece of string or electricians tape at regular known intervals i.e. 50cm or 100cm. Now simply measure across from your line, maintaining a right angle, until the tape touches an object or boundary. Reproduce all of these dimensions on your paper and fill it in like dot to dot and you will have a simple plan.

Recording data To record points of interest, measure along the tape (or, baseline), then take a measurement at right angles from the tape to the point you wish to record. Plot these measurements on to your graph paper. The accuracy of a right angle can easily be checked by basic triangulation (3-4-5 triangle).

BASE LINE Base Lines: It is main and longest line, which passes approximately through the centre of the field. All the other measurements to show the details of the work are taken with respect of this line.

RUNNING MEASUREMENT

OFFSET MEASUREMENT

These are the lateral measurements from the base line to fix the positions of the different objects of the work with respect to base line. These are generally set at right angle offsets. It can also be drawn with the help of a tape. There are two kinds of offsets: 1) Perpendicular offsets, and 2) Oblique offsets.

The measurements are taken at right angle to the survey line called perpendicular or right angled offsets.

The measurements which are not made at right angles to the survey line are called oblique offsets or tie line offsets.

TRIANGULATION

Triangulation triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly (trilateration)