Types of Levelling staff - TS

 A levelling staff (or levelling rod) is a graduated wooden, aluminum, or fiberglass rod used in surveying with an instrument like an automatic or dumpy level. It determines the difference in elevation or relative heights of points on the ground. There are two main categories: 

1. Self-Reading Staff

The surveyor reads the measurements directly through the telescope of the surveying instrument. These are the most common staffs used in the field and include: 

• Solid Staff: A rigid, one-piece staff. Because it cannot fold or retract, it offers high accuracy but is harder to transport.
• Folding (Hinged) Staff: Usually a 3 or 4-meter staff that folds in half using hinges for easy portability.
• Telescopic Staff: Interlocking sliding sections (typically 3 pieces) that pull out to reach lengths of 4 or 5 meters. It is highly compact for storage and transport. 

2. Target Staff

Used primarily for long-distance sightings where reading numbers directly through a telescope is difficult. 

• It features a sliding target fitted with a vernier scale. The instrument operator directs a staff-man on the field to move the target up or down until it perfectly aligns with the crosshair of the leveling instrument. The staff-man then reads the precise measurement from the target. 

Staff Materials

In addition to the physical design, staffs are grouped by the material used to build them:

• Wooden Staff: Traditional and prone to expansion or contraction with temperature changes, though highly seasoned wood minimizes this. 
• Aluminum Staff: Lightweight and resistant to rusting, though it can expand in high heat. 
• Invar Staff: An expensive, highly precise staff constructed with a special nickel-steel alloy that resists thermal expansion. It is used in high-order geodetic surveys. 
• Barcode/Digital Staff: A modern staff with a digitized barcode. It is read by an electronic digital level automatically, eliminating human reading errors.

For any clarification go through the video links   :https://youtu.be/z-EsiZZUAHE

                                                                            :https://youtu.be/GYnWjFgn5oY