About Lesson
Open Cross-Staff
- A simple surveying instrument used to lay out right angles on the ground during chain surveying.
Main Components
a) Head:
- Made of four metal arms with vertical slits.
- Arms arranged to form two perpendicular lines.
- One slit in each line is narrower than the other.
- A horse hair is fixed at the center of the wider slit for alignment.
b) Leg:
- A 25 mm diameter, 1.5 m long pole used to mount the cross-staff vertically on the ground.