THEODOLITE TRAVERSING, PURPOSE AND PRINCIPLES OF THEODOLITE TRAVERSING

Dolat Ram15CRP25

Mehran UET, Jamshoro

THEODOLITE TRAVERSING• Theodolite traversing is a method of

establishing control points, their position being determined by measuring the distances between the traverse stations (which serve as control points) and the angles subtended at the various stations by their adjacent stations.

• The angles are measured by using theodolite and the distances are measured by using the measurement tape or chain.

INSTRUMENTS USED IN THEODOLITE TRAVERSING

Generally, there are two instruments used in theodolite traversing.

1. Theodolite:Theodolite is an instrument used for measuring horizontal and vertical angles. Vertical angles are required for the calculation of elevation of points for example the reduction of slope distance to the horizontal. Horizontal angles are required to obtain the relative direction to a survey control station or points of detail. It gives accuracy upto 1’’.

• Two types: Optical theodolite and Electronic digital theodolite.

2. Chain or Tape:Chain and tape are used to measure the distance

between traverse stations.

Traverse• A traverse consists of a series of straight lines

of known length related one another by known angles between the lines. The points defining the ends of the traverse lines are called traverse stations.

Two types of traverse

1) Open traverse2) Closed traverse

PURPOSE OR OBJECTIVES

• Theodolite traversing is used to compute the area of a traverse.

• To make a traverse survey.• To reduce the field data, adjusting a traverse and

plot the results graphically.• To find the elavation or height of a pole or

building indirectly.• To find the horizontal, vertical and inclined

distances indirectly etc.

PRINCIPLES• A theodolite is an instrument which is capable of

measuring angles to the nearest whole second (1’’). This can be done for both vertical and horizontal angles.

• Vertical angles are required for the calculation of elevation of points for example the reduction of slope distance to the horizontal.

• Horizontal angles are required to obtain the relative direction to a survey control station or points of detail.

Before doing the theodolite traversing survey, there are a few things that must be considered, which are:

• Tripod stand must be in a straight line with the picket (station).

• After setting out, wooden adjustment legs and theodolite must be in a straight line to the picket.

• Value from bearing must be entered correctly.• Distance between one point to the other must be

clearly seen.

When survey was taking on, there are several things that must be clearly taken place; which are:

• The cross hairs must be clearly seen by observer.• The parallax error might be occur when reading was

taken. Therefore the observer must be the same person and very sure that the reading was taken correctly.

• During the changing of left face and right face, be sure that the position of tripod did not change.

• Distance between one point to another was taken correctly.