SURVEYING II
(FOR IV – SEMESTER)
UNIT
I
= TACHEOMETRIC SURVEYING
UNIT II
= CONTROL SURVEYING
UNIT III
= SURVEY ADJUSTMENTS
UNIT IV
= ASTRONOMICAL SURVEYING
UNIT V
= HYDROGRAPHIC AND ADVANCE SURVEYING
PREPARED BY
A.SENTHIL KUMAR,M.E
ASST.PROF/CE

DEPARTMENT OF CIVIL ENGINEERING
UNIT – 2
CONTROL SURVEYING
Working from whole to part - Horizontal and vertical control methods - Triangulation -
Signals - Base line - Instruments and accessores - Corrections - Satellite station -
Reduction to centre - Trignometric levelling - Single and reciprocal observations -
Modern trends – Bench marking
Two Mark Questions and Answers
1. What is trignometric levelling?
Trignometrical levelling is the process of determining the differences of
elevations of stations from observed vertical angles and known distances, which are
assumed to be either horizontal or geodetic lengths at mean sea level. The vertical
angles may be measured by means of an accurate theodolite and the horizontal
distances may either be measured (in the case of plane surveying) or computed (in
the case of geodetic observations).
2. Define geodetic surveying
The object of the geodetic surveying is to determine very precisely the relative
or absolute positions on the earth’s surface of a system of widely separated points.
The relative positions are determined in terms of the lengths and azimuths of the
lines joining them. The absolute positions are determined in terms of latitude,
longitude, and elevation above mean sea level. However, the distinction between
geodetic surveying and Plane surveying is fundamentally one of extent of area rather
than of operations.
3. What is triangulation?
In triangulation, the system consists of a number of inter-connected triangles
in which the length of only one line, called the base line, and the angles of the

triangles are measured very precisely. Knowing the length of one side and the three
angles, the lengths of the other two sides of each triangle can be computed.
4. What are the disadvantages of using triangulation?
The defect of triangulation is that it tends to accumulate errors of length and
azimuth, since the length and azimuth of each line is based on the length and
azimuth of the preceding line. To control the accumulation of errors, subsidiary bases
are also selected. At certain stations, astronomical observations for azimuth and
longitude are also made. These stations are called Laplace Stations.
5. What are the objects of Geodetic Triangulation?
(1) To provide the most accurate system of horizontal control points on which
the less precise triangles may be based, which in turn may form a framework to
which cadastral, topographical, hydrographical, engineering and other surveys may
be referred.
(2) To assist in the determination of the size and shape of the earth by making
observations for latitude, longitude and gravity.

#### You've reached the end of your free preview.

Want to read all 99 pages?

- Spring '20
- Celestial coordinate system, great circle, base line