How Many Types Of Chains Are Used In Chain Surveying?
Chain surveying measure distances using either a chain or a tape. It is a type of land surveying that focuses solely on linear measurements and does not involve angular measurements. This discussion will cover the definition of chain surveying, the principles underlying this technique, the various types of chains in surveying, the instruments employed in chain surveying, the procedure followed in conducting a chain survey, and a diagram illustrating chain surveying. Chain surveying is well-suited for rugged terrains and challenging conditions.
What Is The Principle of Chain Surveying?
Chain surveying uses the triangulation method to divide an area into smaller areas. These measurements are then used to plot a drawing on paper. Chain surveying is also referred to as chain triangulation because the triangulation method is its fundamental principle.
The goal is to form triangles that resemble equilateral shapes, known as well-conditioned triangles. By noting the sequence and lengths of the sides of a triangular survey area, its plan can be easily drawn. However, if the survey area has more than 3 straight boundaries, simply measuring side lengths is not sufficient. The field measurements need to be well-organized to establish triangles and other necessary plans.
5 Different Types of Chains in Surveying
These chains and measuring tapes are essential tools in surveying to accurately measure distances and establish boundaries during land surveys. The choice of the chain depends on the specific requirements of the survey and the desired units of measurement.
1. Metric Chain
The metric chain use stems from the global adoption of the metric system, which is the standard in most countries. The metric chain is typically 20 meters long and divided into 100 links, with each link measuring 20 centimeters. Metric chains come in various lengths such as 5 m, 10 m, 20 m, and 30 m.
These chains used in surveying are equipped with fixed markers at each meter interval for 5 and 10-meter chains, and every 5-meter interval for 20-meter and 30-meter chains. These markers facilitate easier measurement readings and reduce the need for fractional calculations. Additionally, there is a small brass ring present at each meter except where the markers are attached.
2. Revenue Chain
The revenue chain is made of steel and is available in different lengths, typically ranging from 20 meters to 66 feet. It features tallies fixed at each meter, allowing for convenient and accurate readings. Surveyors can easily count the number of tallies to determine the distance covered. Additionally, the Revenue Chain includes brass rings at every meter, except where tallies are attached, ensuring consistent and reliable measurements.
3. Engineer’s Chain
These types of chain in surveying is typically made of high-quality steel, ensuring durability and precision. To use it, surveyors stretch the 100 feet chain along the desired path, making sure it remains straight and taut. Each chain consists of around 100 links, usually measuring 20 cm in length, with brass or steel rings placed at every meter.
4. Band Chain or Steel Band
It consists of a series of links, usually one meter in length, with markings for easy measurement. Surveyors employ band chains by stretching them between two points and counting the number of links to determine the distance. The bands are resistant to stretching, ensuring reliable measurements.
These types of chains in surveying consist of a lengthy, narrow strip of steel with a consistent width ranging from 12mm to 16mm and a thickness of 0.3mm to 0.6mm. To divide the chain, brass studs are placed at intervals of 20cm. Alternatively, band chains may have graduated markings in centimeters instead of brass studs.
In surveying, band chains are conveniently wrapped around steel crosses or metal supports for easy unrolling and usability. These steel bands are available in lengths of 20m and 30m, with a width of approximately 12mm to 16mm.
5. Gunter’s Chain or Surveyor’s Chain
The chain consists of a series of interconnected links, typically made of steel or brass. Its standardized length of 66 feet (20.12 meters) facilitates easy conversion into acres, a commonly used unit for land measurement. Surveyors employ this chain by stretching it along the desired path and securing it with marking stakes.
This particular type of chain used in surveying has a length of 66 feet for the sake of convenient measurement. It is worth noting that 10 square chains are equivalent to 1 acre. Furthermore, when linear measurements are needed in furlongs and miles, this chain proves to be more convenient, as 10 chains constitute 1 furlong and 80 chains constitute 1 mile.
7 Types of Instruments Used in Chain Surveying
To conduct an effective chain survey in India, you would need the following instruments:
1. Chain
A measuring chain is an essential tool in chain surveying. It consists of a series of connected metallic links, typically made of steel or brass, with a known length, such as 66 feet or 100 feet. These chains consist of straight links created from galvanized mild steel wires that are curved into rings at the ends of these wires. These curved rings are connected using three small circular rings.
Swivel joints are attached to the chain’s ends to allow for easy turning without causing any twists. The length of a surveying chain link is the distance between the two consecutive middle rings measured from their centers, while the overall length of the surveying chain is measured from the outer handle of one end to the outer handle of the other end.
2. Ranging Rods
Ranging rods, also known as range poles, are available in lengths of 2m or 3m and typically possess a circular shape with a diameter of 30mm. They are painted with alternating bands of white and red or white and black, each band being 200mm wide. To safeguard the rod from damage, the lower ends are equipped with a steel shoe spanning 150mm in length. Ranging rods serve the dual function of ranging and marking stations to ensure accuracy and consistency.
3. Arrows
The different types of chains in surveying consist of arrows made of steel wires with a diameter of 4mm, measuring approximately 400mm long. The wire is shaped into either a hook or a ring at one end, and it tapers to a sharp point at the other end. The ring serves as a handle for carrying the arrow, while the pointed end facilitates its insertion into the ground. Typically, a group of 10 arrows is transported together using a chain, with the arrows inserted at the chain’s end.
4. Cross Staff
A cross-staff, also known as a ranging rod cross, is used to determine right angles or to set up perpendicular lines during the survey. It consists of two perpendicular-ranging rods or poles joined together.
5. Plumb Bob
A plumb bob is a weighted object attached to a string. It is used to establish vertical lines or to determine the true vertical position of a point.
6. Measuring Tape
While a type of chain in surveying is commonly used for linear measurements, a measuring tape can also be used as an alternative for smaller distances or in situations where a chain is not available.
7. Field Book
A field book or survey notebook is used to record all the measurements, observations, and calculations made during the survey. It helps in organizing and documenting the data for later analysis and mapping.
A Final Word On Types Of Chain In Surveying
It is important to note that modern surveying techniques may incorporate electronic instruments such as total stations or GPS receivers for more accurate and efficient data collection. However, the instruments mentioned above are the traditional tools used in chain surveying, which is still commonly practiced in certain situations in India.
