SURVEY STATIONS
SURVEY STATIONS
Survey stations are the points at the beginning and at the end of the chain line. They may
also occur at any convenient position on the chain line. Such stations may be :
(a) Main stations (b) Subsidiary stations (c) Tie stations
(a) Main stations : Stations taken along the boundary of an area as controlling points
known as ‘main stations’. The lines joining the main stations are called ‘main survey
lines’. The main survey lines should be cover the whole area to be surveyed. The main
stations are denoted by ‘ ’ with letters A,B,C,D, etc.
(B) Subsidiary stations : Stations which are on the main survey lines or any other survey
lines are known as ‘Subsidiary stations’. These stations are taken to run subsidiary lines
for dividing the area into triangles , for checking the accuracy of triangles and for
locating interior details. these stations are denoted by ‘ ‘ with letters S1, S2, S3, etc.
(c) Tie stations : These are also subsidiary stations taken on the main survey lines. Lines
joining the tie stations are known as ‘tie lines’. Tie lines are taken to locate interior
details. The stations are denoted by ‘ ’ with letters T1 , T2 , T3 , etc.
(2) MAIN SURVEY LINES : The lines joining the main stations are called ‘main
survey lines’ or chain lines in fig. AB,BC,CD and DA are the main survey lines.
(3) BASE LINE : The line on which the framework of the survey is built is known as the
‘base line’ . It is the most important line of the survey .Generally , the longest of the main
survey line is considered as the base line. This line should be measured very carefully and
accurately. In fig. BD is the base line
(4) CHECK LINE : The line joining the apex point of a triangle to some fixed points on
its base is known as the ‘check line’. It is taken to check the accuracy of the triangle .
Sometimes this line is helps to locate interior details .In fig.CS1 , AS2 are the check lines.
(5) TIE – LINE : A line joining tie stations is termed as a tie line. It is run to take the
interior details which are far away from the main lines and also to avoid long offsets. It
can also serve as check line. In Fig. T1 T2 is the tie line.
PROCEDURE:
(1) Fix station A and B at some distance by fixing wooden peg to determine horizontal
distance between them.
(2) Position of station A and B is fixed by measuring their position from at least three
permanent objects and location sketch of station A and B are drawn.
(3) The follower holds one handle of the chain in contact with peg at station A.
(4) The leader takes the other handle of the chain, arrows and ranging rod & walks in the
forward direction dragging chain with him.
(5) After the chain is stretched completely along the line the follower steps on one side of
the line with the ranging rod touching the handle.
(6) The follower directs to leader to stand exactly in the line. The leader puts a scratch at
the position & inserts an arrow. He then moves forward with the chain handle with the
remaining arrows and ranging rod till the follower reaches the next arrow point.
No comments:
Post a Comment