Chain surveying is a type of surveying method that involves the use of a chain or tape to measure distances and angles on the ground. In this method, various measurements are taken to determine the position and dimensions of objects or features on the land. One of these measurements is known as offsets.

Offsets in chain surveying refer to the lateral measurements that are taken from the chainage (the starting point of the measurement) to the objects or features being surveyed. These lateral measurements are perpendicular to the chain line and are used to determine the distance and location of the objects from the chain line.

Offsets are typically measured using a perpendicular offset rod or a tape measure. The surveyor positions themselves at the chainage and then measures the distance from the chainage to the object in a perpendicular direction. This measurement is the offset distance.

Offsets are important in chain surveying as they allow for the accurate plotting of the objects or features being surveyed. By measuring the offset distances, the surveyor can determine the exact position of the objects in relation to the chain line. This information is then used to create an accurate map or plan of the surveyed area.

In addition to measuring offset distances, other measurements are also taken in chain surveying. These include backsights, check lengths, and forward offsets.

- Backsights are measurements taken from a previously surveyed point back to the current point. They are used to ensure that the survey is being conducted along a straight line and to check for any errors in the measurements.
- Check lengths are measurements taken at regular intervals along the chain line to ensure that the chain or tape is being properly stretched and that accurate measurements are being obtained.
- Forward offsets are measurements taken from the chain line to objects or features in the forward direction. They are used to determine the dimensions and positions of these objects.

In conclusion, offsets are the lateral measurements taken from the chainage to objects or features in chain surveying. They are important in accurately positioning and mapping these objects in relation to the chain line.