What is Chain Surveying

What is Chain Surveying

Chain surveying is that type of surveying in which only linear measurements made in the field. Surveying is suitable for surveys of the small extent on open ground to secure data for an exact description of the boundaries of a piece of land or to take simple details. The principle of chain survey or Chain Triangulation, as is sometimes called, is to provide a skeleton or framework consists of a number of connected triangles, as the triangle is the only simple draw that can be plotted from the lengths of its sides measured in the field book.

To good results in plotting, the framework should be consist of triangles which are as nearly equilateral as possible. Also, read: What Is Bulkage of Sand (Fine Aggregate)

Principle of Chain Surveying

The principle of chain surveying is triangulation. This means that the area to survey is spilled into a number of small triangles which should be well-conditioned.

In chain surveying, the side of the triangles are measured directly from the field by chain or tape, and no angular measurements are used. Here, the check lines and tie lines control the accuracy of the given work.

It is noted that plotting triangles requires no angular measurements to be made if the three sides are known.

Chain surveying used in this situation

More or less level of the ground surface.

A small area is to be surveyed.

A small-scale map is to be prepared.

The formation of well-conditioned triangles is easy.

Chain surveying is unsuitable when

The area is crowded with many details.

The area consists of too many undulations.

The area is very large.

The formation of well-conditioned triangles becomes difficult because of obstacles.

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Procedure of Chain Surveying

Baseline, Tie line, Check line, Main survey stations, Tie Stations, Location sketches of survey station

Two men are required to measure the distance between two places A and B by a chain.One man who grabs the ends of the chain and pulls it forward is called the forerunner and the other, the one that is called the back end of the chain.

The precursor is given a drawing bar and 10 arrows when measuring by a chain.

A knob in the groove inside the handle of the succeeding chain holds the handle of the chain exactly as it is mounted, pressing it down the heel of the foot, and pulling the chain from the forearm to the perpendicular line to the line AB.

Then, with the instructions to the succeeding precursor, the trajectory moves line AB to the left or right, until the straight line connecting the points A and B is reached.

When the drawing is done correctly, the forearm points to the ground where the forearm is fine, with two lines cutting off each other, with the help of a forward shaft or if the ground is hard.Then the handle of the forearm chain instantly grabs the chain with both hands and pulls it exactly above the mark on the ground.

Now the precursor takes one of the ten arrows held by it and knocks it in the semicircular groove provided at the outside of the handle of the chain.

These arrows indicate the end of a chain. Now the forward chain is pulled forward.And when the next arrow is dropped, it stops the pioneer from moving forward. Then he will be there for himself

And when the next arrow is dropped, it stops the pioneer from moving forward. Then he will be there for himself

The arrow drawn in the groove of the handle of the chain holds the handle in a manner that fits exactly between the two-legged and draws the forearm to the line AB by drawing as described above.

Then pull the leading chain straight and end at it. Moves the arrow as described above.

He then pulls the chain forward and lifts the lost arrow in the ground before the successor moves behind it.

In this way, the process of quantification is repeated until it reaches position B.

The precursor is usually given 10 arrows at the beginning. Since the precursor picks up the lost arrow successor, the number of arrows should be ten at any given time.

By doing so, it is not possible to forget the length of the entire chain by measuring the distance.

The number of chain-lengths measured by the arrow that comes to the successor is calculated.

When all 10 arrows are moved to the successor, they note the field and give it to the forearm, thus measuring the distance.

Finally, when the portion of line AB whose length is less than one entire chain remains to be measured, it is precisely drawn to measure the leading chain B reads the distance in front of the link and reports the successor in the field.

Subsequent drawings have to be made when measuring distances, and the measured distances have to be noted in the field book.

Thus his responsibility is more than the foregoing.

Therefore, experienced and intelligent surveyors should be entrusted with the task of succession. Procedure Chain Surveying

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Obstacles in Chain Surveying

Ranging obstructed

Chaining obstructed

Possible to chain around the obstructed

Impossible to a chain around the obstacle

Obstructed in Chaining & Ranging

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Technical terms of Chain Surveying

Base line

Tie Line

Check Line

Main survey stations

Tie Station

Offset

Method of Taking Offsets

Oblique Offsets

Range tie and Check tie

Location Sketches of a survey station

1. Base Line

Chain survey graphs. The three lines of a triangle that depend on one line are called the base lines.

The accuracy of the chain survey, based on the accuracy of the baseline. Is dependent

For this, the long line between the survey structure and the line between the region is taken as the base line. Based on the line and even flat ground, the measurement is chosen in a way that is less difficult.

Base, the line should be measured at least twice in the opposite direction. On the map, the survey lines are displayed along the dotted lines and in the middle of the breaks.

2. Tie line

Vertical when the main survey lines pass away in detail the length of the.

To minimize this length, a secondary line (T1, T2) that is closest to the details is selected, as shown in the drawing

By doing so, it would be shorter to take the details vertically, be more precise. And time is saved.

This secondary line is called the coincidence line. The accuracy of the survey triangles is also tested as these coincidence lines connect the two points above the main survey lines.

3. Check line

If you know the length of the sides of a triangle, then a triangle can be drawn, but it is not possible to measure the length of the sides of the error drawn.

For this, a lock line is kept in each triangle.

The bottom line is the line connecting the main survey location and any known location above it.

An error is made when comparing the measured length of this line with the drawn length on its map.

In this way, the measurements were taken over the field, and the accuracy of their plotting is tested.

4. Main survey stations

The vertices of the survey triangles are called the main survey locations. The following are some things to keep in mind when choosing this survey location

A well-formed triangle should be drawn along the line connecting the survey location.

The main survey line should be as low as possible.

Surface and the open area should pass through till baseline is formed.

The main survey line should pass through the details and until they are made parallel so that the vertical is shortened.

Each triangle must have a lock line.

There should be as little difficulty as possible in placing and drawing the length of the survey line.

All survey lines should pass through the flat ground.

On high-traffic roads, the survey line should pass over one side of the road so as not to cause frequent interruptions in the measurement, as well as not to disturb the vehicles.

Major survey locations are usually 6 mm on the map. The diameter is shown from the circle and the name of the survey space in the circle, for example, A, is typed.

5. Tie station

The coincidence line is called the coincidence location of the survey locations on both ends. This coincidence is located on the main lines.

Coincidence locations are 6 mm above the map. The long-sided equilateral triangles are shown.

6. Offset

Lateral measurements are taken from the survey line to the left and right of the survey line to determine the location (Offset in surveying).

These lateral dimensions are called offsets. There are two types of offset

Vertical offset

Oblique offset

7. Range tie and check tie

When the details of a building, a building, a fence, etc. are located at the most oblique angle of the survey line, their positioning, as shown in Drawing, is done by coincidence.

The building is located diagonally to the PQRS survey line AB. The line that connects the QP side of the house extends to the survey line. This point is the base of the t-traction combination, and Pt is the basis of the traction combination.

Similarly, p is the basis of the Pp traction coincidence found in extending SP.

QR is also a trace coincidence

8. Location sketches of stations

he survey of the vast region cannot be completed in a day.

So there is the danger of leaving the survey site open.

So we have to reschedule the survey location at any time

A graph of each survey location is created to be taken.

After selecting the survey location, the location is fixed with an incorrect location.

The survey site is displayed with oily colors or white on the asphalt or cement road.

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Recording the measurements in the Field Book (Field Measurement Book)

The book in which the chain or tape measurements are entered is called the field book. It is an oblong book of size about 20 cm x 12 cm and opens lengthwise.

The main requirements of the field book are that it should contain good quality stout opaque paper. it should be well-bound and of a size convenient for the pocket.

The chain line may be represented either by a single line or by two lines spaced about 1 to 2 cm apart. ruled down the middle of each page.

The double line field book as per below drawing no-1 is most commonly used for ordinary work, the distance along the chain being entered between the two lines of the page.

Single filed book

Single Line Filed Book No 1

Single line field book as per above drawing no-1 is used for a comparatively large scale and most detailed dimension work.

A chain line is started from the bottom of the page and works upwards.

All distances along the chain line are entered in the space between the two ruled lines while the offsets are entered either to the left or to the right of the chain line, as the case may be.

Offsets are entered in the order they appear at the chain line. As the various details within offsetting distances are reached, they are sketched and entered as shown in as per the above single line filed drawing no-1 and as per below drawing no-2 Every chain line must be stained from a fresh page. All the pages must be machine numbered.

The three main obstacles in chaining of a line are of the following types: 1. Chaining Free, Vision Obstructed 2. Chaining Obstructed, Vision Free 3. Chaining and Vision Both Obstructed.

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