Chain Surveying

Principles of Chain Surveying or Linear Surveying | Civil Engineering

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Chain Surveying or Linear Surveying | Surveying and Levelling

It is the method of land surveying in which only linear measurements are made.

Chain surveying requires chain, tape and ranging rods.

Chain surveying is not suitable for large areas having many details.

(The term “details” means a natural or manmade features at or near the ground surface).

Chain Surveying
Chain Surveying

It consists of the following:

Hard details

Hard details include buildings, roads, walls etc.

Soft Details

Soft details include river, vegetation, trees etc.

Overhead details

Overhead details include power and telephone lines.

Underground details

Underground details include survey of water mains, sewer etc.

Principles of Chain Survey

A triangle is a simple figure which can be plotted from the lengths of three sides even if the angles are not known.

In chain survey, the area to be surveyed is divided into a framework consisting of triangles.

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Types of Ranging | Chain Surveying

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Methods of Ranging in Chain Surveying | Guide to Surveying and Levelling

In measuring a survey line, the chain has to be laid out on the ground between the stations.

If the line is short, the chain could be put in alignment easily but if it is long or the end station is not clearly visible, then intermediate points has to be established in line with end points to know the directions of the line by ranging.

Types of Ranging

There are two types of ranging:

  1. Direct ranging
  2. Indirect ranging

Direct ranging

Direct ranging is possible when the stations are intervisible.

Ranging is done by eye-judgement. Ranging rods are erected vertically beyond each end of survey line.

The surveyor stands 2m beyond the ranging rod while the assistant folds the ranging rod vertically in the intermediate stations.

The ranging rod is held roughly in line by the thumb and fore-finger.

The surveyor directs the assistant to move the rod to the left or right until the three ranging rods appear to be in a straight line.

To avoid errors due to the ranging rods not being vertical, the lower end of the rod are cited for alignment.

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Errors in Chaining | Guide to Surveying and Levelling

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Types of Errors occurring in Chain Surveying

There are two types of Errors that are commonly seen to occur in Chain Surveying. For students studying the concept of Chain Surveying, study of the occurrence of different types of Errors in Chain Surveying is important. In this article, we will briefly discuss different types of Errors in Chain Surveying and the situations in which they occur.

Types of Errors:

  1. Cumulative error
  2. Compensative error

Cumulative error

These errors always accumulate in one direction and are serious in nature. They affect the survey work considerably.

They make measurements too long or too short.

These errors are of two types and are known as systematic errors.

They are classified as follows:

  1. Positive error
  2. Negative error

Positive error

These errors make the measured length more than the actual length which results into wrong calculations by the Surveyor.

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Field work in Chain survey | Surveying in Civil Engineering

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Field work in Chain surveying | Surveying and Levelling

Earlier, we discussed “Principles of Chain Surveying” and the considerations that are taken for carrying out Chain Surveying… In this article, we will discuss various instruments that are essential for carrying out Chain Surveying.

Here are the steps to be followed for carrying out Chain Surveying:

  1. Reconnaissance Survey
  2. Marking stations
  3. Running survey lines
  4. Taking offsets

Instruments used in Chain Survey

  1. Chain, 20m or 30m long
  2. Tape
  3. Arrows
  4. Ranging rods
  5. Wooden or Iron Pegs
  6. Plumb bob
  7. Cross staff

Chain used for Surveying

20m chain – 100 links

30m chain – 150 links

1 links – 20cm

Links of chain are made by mild steel wire – 4mm diameter.

Chain used for Chain Surveying
Chain used for Chain Surveying

Each link at the end is bent into a loop and is connected to adjoiningly by means of three oval rings which offers flexibility to the chain. Ends of chains carry brass handle.

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