THEODOLITE LESSON 7
TRAVERSING
•
A traverse consists of several sides or lines connected each other
continuously as shown in figure 1
TYPES OF TRAVERSE
•
Closed traverse
First and last point meets on the same station
(Figure 2)
•
Open traverse First and last point do not meet on the
same station (Figure 3)
Stages of conducting traverse
•
Reconnaissance
survey
•
Selection and
marking of stations
•
Running of
survey lines (sides)
•
Locating the
details
•
Booking the
field notes
•
Measuring the
distances preferably with steel tape
Methods of traversing
•
Direct
observation of angles between successive survey lines
•
Direct
observation of bearings of survey lines
Direct observation of angles between successive survey
lines
•
Traversing by
the method of included (Interior or Exterior)
•
Traversing by
the method of direct angles
•
Traversing by
the method of deflection angles
Traversing by the method of included angles (Interior
or exterior)
•
This method is used where greater accuracy is required.
• In this method, included angles of successive stations
are measured by taking bearings of
previous line and later.
Measurement of included angles
•
Angles PQR,QRS RST, STP, and TPQ
are the exterior angles of a traverse as
shown in Figure 4
Note:
These angles occur if the traverse is in clock wise direction
•
Angles VPQ, PQR,QRS, RST,STU, TUV, and UVP are the interior angles of a traverse as shown in Figure 5
Note:
These angles occur if the traverse is in anti clock wise direction
•
Set up theodolite over station “P” and complete the temporary
adjustments accurately ( see figure-4)
•
Bring index of verniers “A” to zero degrees
•
Release lower plate clamp screw and sight to magnetic
north
•
Bisect the station “Q” accurately with the help of
corresponding slow motion screw
•
Read main scale and corresponding vernier scales “A”
and “B”. This angle is called bearing of line “PQ”
•
Bring the index of veriners to zero
•
Set up theodolite over station “Q” and complete the
temporary adjustments accurately
•
Sight to the
station “P” accurately
•
Unclamp the upper clamp screw and sight to station “R
•
Read main scales and corresponding vernier scales
•
Angle PQR is an exterior angle
•
Continue the same procedure at other stations
•
Measure the distances simultaneously
•
Enter the readings in the profarma
•
Take the readings with face right for further accuracy
Note: Follow the same procedure for the
traverse in anti clockwise direction
Traversing by the method of direct angles
•
Direct angles
are those which are measured clock wise from the preceding line to the
following line
The
following figure shows the traverse by direct
angles
•
Set up the Theodolite at station “A”, level it
accurately and observe the bearing of line “AB”
•
Set up the Theodolite at station “B” and level the
Theodolite accurately and set vernier “A” to zero
•
Loosen the lower clamp and sight to the preceding
station “A” and bisect the station exactly
by corresponding slow motion screw
•
Release the upper plate and rotate the telescope clock
wise and bisect the forward station “C”
accurately
•
Read both verniers. The mean of the two readings will
give the direct angle “ABC”.
•
Repeat the same work with face right of the theodolite
•
The mean of the two readings will give the direct
angle “ABC”
•
Take the average of readings taken by both faces for
further accuracy
Traversing by the method of Deflection angles
Deflection
angle:
It is the angle made by a survey
line with respect to the extended line of previous line
Angle
B’BC – Left deflection Angle
Angle
C’CD – Right deflection Angle
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