Introduction Of Chain survey
Chain surveying is a traditional method of land surveying that involves the measurement of distances and angles using a chain or tape measure. While modern surveying techniques have largely replaced chain surveying in many applications, it is still used in certain situations, especially in areas with challenging terrain. The basic instruments used in chain surveying include:
Instruments used in chain surveying
1.Chain or Tape Measure:
- Chain: Historically, a chain made of metal links was commonly used. The Guntur chain and the Engineer’s chain are examples.
- Tape Measure: Nowadays, steel or fiberglass tapes are more common due to their flexibility, ease of use, and accuracy.
- Ranging rods are used to mark the ends of the survey line. They are typically made of wood or metal and painted in contrasting colors for easy visibility. Ranging rods help in aligning the chain or tape during measurement.
3.Arrows and Flags:
- Arrows or flags are attached to ranging rods to make them more visible, especially over long distances or in challenging terrain.
- The cross staff is used to set perpendicular lines during the survey. It consists of two arms joined at right angles, and it helps in setting right angles from a baseline.
- A prismatic compass is used for measuring angles. It consists of a magnetic needle and a prism that allows the user to simultaneously sight the target and read the magnetic bearing.
- A plumb bob is used to ensure that ranging rods are vertically aligned. It helps in establishing accurate vertical points.
- Ranging poles are used for marking intermediate points along the survey line. They are shorter than ranging rods and help in maintaining a straight line between the end points.
- A tripod stand is used to support the prismatic compass or other instruments at a desired height and stability.
- Offset rods are used to measure perpendicular distances from the survey line to features or objects of interest.
10.Leveling Instruments (optional):
In some cases, a dumpy level or a leveling instrument may be used to establish horizontal lines or elevations.
It’s important to note that while chain surveying has its applications, modern surveying techniques like total stations, GPS, and GIS have become more prevalent due to their higher accuracy, efficiency, and ability to handle complex surveying tasks.