One of the following surveying instruments is used to set out lines at right angles to the main chain line?
Answer Details
The surveying instrument used to set out lines at right angles to the main chain line is the optical square. An optical square is a small device that has a built-in spirit level and a sighting mechanism. The spirit level helps to ensure that the device is level and the sighting mechanism helps to align the device with the main chain line. By using an optical square, surveyors can easily set out lines that are perpendicular to the main chain line.