Accessories of linear measurement 

A. Chain 
B. Tape
C. Peg
D. Arrow 
E. Ranging rod 
F. Offset rod 
G. Plumb bob

A. Chain 

It is a type of linear measurement. It is formed by several links having a fixed length provided with circular ring with handles at both ends with swivel joints. 

chain in surveyingSo that, the chain may be turned without twisting. The chain is available in several in numerous different lengths. Generally it's in 5 m,10 m,20 m,and 30 m.

There are following types of chain are as follows :-

1. Metric chain
2. Guntor'S chain 
3. Engineer's chain 
4. Revenue chain 
5. Steel band chain 

1. Metric chain

                  The chain in which a reading is taken in metric system is called metric chain. It is generally available in 5 m, 10 m, 20 m,and 30 m. In 5 m and 10 m chain, tally are provided at each one meter length. 

• It is made up of galvanized mild steel wire. 
• Handle is made up of brass. 
• In 20 m, and 30 m chain, tally are provided at each 5 m length and every 1m length ring is provided. 

2. Guntor's chain 

                     In this chain, 100 links are attached to form a length of 66 feet and each link length is 0.66 foot. This chain is used in convenience land measure due to following advantages.

                     

                     10 square chains = 1 Acre

                     10 chains = 1 Furlong 

                     80 chains = 1 Mile

                     8 furlong = 1 mile

3. Engineer's chain

                         The length of this chain is 100 feet. They consist of 100 links. Any link length is 1 foot. Tally are provided at every 10 links (10 feet) and central tally can be round.

4. Revenue chain

                      The length of this chain is 33 feet and consist of 16 links. Hence, each link will be two and one sixteenth feet. It is mainly used in codastral survey.

5. Steel band chain( Band chain) 

                          It is consist of a steel having width 12 mm to 16 mm and thickness 0.32 mm to 0.66 mm. It is available in length of 20 m,and 30 m. 

It has a brass handle at each ends. The readings are marking in meter, decimeter, or centimeter one side. 

The steel band is used in projected area where more accuracy is required.

Advantages of chain

• They can be ready easily & quickly. 
• They can with stand wear and tear. 
• They can be easily repaired in the field. 

Disadvantages of chain

• They are heavy and take an excessive amount of time to open or fold. 
• They become longer or shorter because of continuos use. 
• When the measurement is taken in suspension the chain sag excessively.

B. Tape 

It is also linear measuring instrument by which a distance can be measured more accurately than a chain. 

Generally it is available in 2 m, 5 m, 10 m, 20 m, 25 m, 50 m, 100 m,and also in feet such as 33 feet, 50 feet, 66 feet, and 100 feet available in market. 

There are following types of chain are as follows :-

1. Cloth or linen tape 
2. Metallic tape 
3. Steel tape
4. Inver tape

C. Peg 

It is used to mark the position of the station or terminal point of a survey line. It is made up of seasoned timber. 

Generally upper surface of peg is 2.5 cm square or 3 cm square and 15 cm length tapered at the end. They are driven into the ground with the help of wooden hammer.

D. Arrow 

It is made up of steel wire of 4 mm diameter. One end of the arrow  is bent into a ring of 50 mm diameter and other end is inserted in the ground. It is used for the counting number of chains.

E. Ranging rod

It is made up of well seasoned straight timber which is used ranging rod and offset rod ranging rods are used forranging rod in surveyingfor ranging the intermediate points in the survey line. Generally it is available in 2 m & 3 m length. 

It can be easily inserted in the ground. It is painted in alternative colour/ band of either black or white. Each bands being 20 cm or 0.2 m depend upon ranging rod.

F. Offset rod

It is similar to ranging rod which is used for drawing offset on survey line. It is available in 3 m and alternatively coloured in black & white. 

It is painted with iron shoe at one end and provided with notch or hook on the other end.

G. Plumb bob

It is an instrument which is used for transferring the height to the ground. It is also used in centring the theodolite, compass and plane table in survey.

plumb bob in civil engineering