This is the simplest and oldest form of land surveying of an area using linear
measurements only. It can be defined as the process of taking direct measurement,
Equipment Used In Chain Survey
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| Chain survey Equipment |
For Chain Surveying Equipment used can be divided into Three Namely,
1) Those used for linear
measurement. (Chain, steel band, linear tape)
2) Those used for slope
angle measurement and for measuring right angle (Eg.Abney level, clinomater, cross
staff, optical squares)
3) Other items (Ranging
rods or poles, arrows, pegs etc).
* Chain:- The chain is usually made of
steel wire, and consists of long links joined by shorter links. It is designed for
hard usage, and is sufficiently accurate for measuring the chain
lines and offsets of small surveys.
Chains are made up of links which
measure 200mm from centre to centre of each
There are Three Different Types of chain used for Taking measurement named:
i. Engineers chain
ii. Gunter’s chain
iii Steel bands
* Steel Band :- This may be 30m, 50m
or 100m long and 13mm wide. It has handles similar to those on the chain and is wound
on a steel cross. It is more accurate but less robust than the chain. The
operating tension and temperature for which it was graduated should be indicated on
the band.
* Tapes:- Tapes are used where greater
accuracy of measurements are required, such as the
setting out of
buildings and roads. They are 15m or 30m long marked in metres,centimeter and millimeters. Tapes
are classified into three types;
i. Linen or
Linen with steel wire woven into the fabric:
ii. Fibre Glass
Tapes: These are much
stronger than lines and will not stretch in use.
iii. Steel tapes: These are much more
accurate, and are usually used for setting out buildings and
structural steel works. Steel tapes are available in various lengths up to
100m (20m and 30m being the most common) encased in steel or
plastic boxes with a recessed winding lever or mounted on open frames with a folding
winding lever.
* Arrows:- Arrow consists of a piece of
steel wire about 0.5m long, and are used for marking
temporary stations. A
piece of coloured cloth, white or red ribbon is usually attached or tied to the end of
the arrow to be clearly seen on the field.
* Pegs:- Pegs are made of wood 50mm x 50mm
and some convenient length. They are used for points which are
required to be permanently marked, such as intersection points of survey lines. Pegs are
driven with a mallet and nails are set in the tops.
* Ranging Rod:- These are poles of circular
section 2m, 2.5m or 3m long, painted with
characteristic red and white
bands which are usually 0.5m long and tipped with a
* Opticle square:- This instrument is used for
setting out lines at right angle to main chain line. It is used where greater
accuracy is required. There are two types of optical square,one using two mirrors
and the other a prism.
• The mirror method is
constructed based on the fact that a ray of light is reflected
• The prism square
method is a simplified form of optical square consisting of a single prism. It is
used in the same way as the mirror square, but is rather more accurate.
* Cross Staff:- This consists of two pairs of
vanes set at right angle to each other with a wide and narrow slit in each vane. The
instrument is mounted upon a pole, so that when it is set up it is at normal eye level.
It is also used for setting out lines at right angle to the main chain line.
* Clinometer:- This instrument is
used for measuring angles of ground slopes (slope angle).
They are of several form, the common
form is the WATKING’S CLINOMETER, which consist of a small
disc of about 60mm diameter. A weighted ring inside the disc can be made to hang free
and by sighting across this graduated ring angle of slopes can be read off. It is
less accurate than abney level.
* abney Level:- This instrument is generally used
to obtaine roughly the slope angle of the
ground. It consists of a
rectangular, telescopic tube (without lenses) about 125mm long with a graduated arc
attached. A small bubble is fixed to the vernier arm,once the image of
the bubble is seen reflected in the eyepiece the angle of the line of sight can be read off
with the aid of the reading glass.
General Procedure in Chain Surveying:-
1. Reconnaisance:- Walk over the area to
be surveyed and note the general layout, the position of features
and the shape of the area.
2. Choice Of Station:- Decide upon the framework to
be used and drive in the station pegs to mark the stations
selected.
3. Station Marking:- Station marks, where possible
should be tied - in to a permanent objects so that they may be
easily replaced if moved or easily found during the survey. In soft ground wooden
pegs may be used while rails may be used on roads or hard surfaces.
4. Witnessing:- This consists of
making a sketch of the immediate area around the station showing existing
permanent features, the position of the stations and its description and designation.
Measurements are then made from at least three surrounding features to the
station point and recorded on the sketch.The aim of witnessing is to
re-locate a station again at much later date even by
others after a long interval.
5. Offsetting:- Offsets are usually
taken perpendicular to chain lines in order to dodge obstacles on the chain line.
6. Sketching:- The layout on the last page of
the chain book, together with the date and the name of the surveyor, the
longest line of the survey is usually taken as the base line and is measured
first.
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