In my previous post I have discussed about the procedure, principle and only brief introduction of instruments used in chain surveying. In this post I am going to elaborate in detail about the equipment used in chain surveying. All the chain surveying tools or types of chains that and used in surveying along with their features.
[su_box title=”Pro Tip” style=”bubbles” box_color=”#22c55e” radius=”5″]You can read about introduction to chain surveying from this post. [/su_box]
List of Instruments used for Chain Surveying
The following are the tools and equipments that I had mentioned in my previous post :-
- Ranging Rods
- Offset Staff / Rods
- Plum Bobs
Arrows also known as making pins or chaining pins are made of tempered steel wire 4mm in diameter and generally 10 arrows are supplied with a chain.
Usually the arrow mark the end of chain during process of chaining. An arrow is inserted into the ground after the chain length is measured on the ground. Usually the length of an arrow is 40cm and one end of it is made sharp and the other end is bent into a circle for facility of carrying.
They are made up of good quality hardened and tempered steel wire of 4mm in diameter. The arrows are made 400 mm in length. They are pointed at one end of inserting in to the ground. The other end is in to a ring.
Pegs are made of hard wood or iron and are 40 mm square by 50 cm in length and are used for permanently marking positions during survey.
These rods are tapered at one end, generally 25mm or 30mm square and 150mm long wooden pegs are used to mark the position of the station on. In soft ground 40 to 60 cm long and 4 to 5 cm square is suitable.
They should be driven in the ground with about 4 cm lengths, projecting above the ground.
As you are about to execute chain surveying so chain is the requisite tool that is a must. A chain is made up of steel or galvanized mild steel wire which is divided into straight links and tags (rings) to facilitate folding and for ease in storage.
The ends of each link are bent into a loop hand connected together by means of three oral rings. For ease in dragging the chain on ground brass handles are provided at the ends.
The length of chain is measured from outside of one handle to the outside of the other while the length of a link is the distance between the centers of two consecutive middle rings.
Chain is used as unit of measurement for horizontal distances in chain surveying. It has brass handles at both ends for easy handling. The links is 0.2 m or 200 mm in diameter. The length is 20 m or 30 m.
The metallic rings or tags are attached with chain to facilitate quick reading of the fraction of a chain in surveying measurement. Different types of chains used in surveying are based on their length and are as follows:-
- Metric chains
- Steel band or Band chain
- Gunter’s chain or surveyor’s chain
- Engineer’s chain
- Revenue chain
The ranging rods are used for making the intermediate positions / points of stations and for ranging the lines. They are made of seasoned straight grained timber of teak, blue pine, sisov or deodar. They are circular or octagonal in cross section with 3cm diameter and have a length of either 2 or 3 m. They are painted alternatively black and white or red and white.
They are shod at the bottom with a heavy iron points. In order to make them visible at a distance, they are pained alternatively black and white or red and white. When they are at considerable distance, red and white or white and yellow flags about 25 cm square should be fastened at the top.
Offset Staff / Rods
Similar to the ranging rod, they are usually 3 m long and is divided into parts each 0.2 m length. On top open ring for puling or pushing the chain through a wedge.
The offset rod is used for measuring the offset of short lengths. It has two short narrow vertical slots. It is used for aligning short offsets.
While chaining along sloping ground, a plumb bobs is required to transfer the points to the ground. It is also sometimes used for testing the verticality of ranging poles.
The surveyor’s band is made of a steel strip which is rolled into a metal frame with a winding handle. It is 30m, 50m or 100m long. It is used in projects where more accuracy measurement is required.
The cross staff is made of metal or wood with eye slips at right angles and is used to measure right angles from the line of traverse
In order to note the readings of chain survey a note book or surveyor’s book is used.
In this post I have enlisted and explained all the tools and instruments used in chain surveying. Knowing instruments before start of any work is very important as far as success or failure of the surveying is considered. There are different types of chains that are used in chain surveying all of these are also enlisted.