25.2 : Leveling Equipment

As leveling involves measuring vertical distances relative to a horizontal line of sight, it requires a graduated rod, called a level rod, for vertical measurements and an instrument called a level for a horizontal sight line. A level includes a high-powered telescope with a mechanism for leveling to ensure the line of sight is horizontal when the bubble in the spirit level is centered. Leveling rods, made of wood, metal, or fiberglass, are graduated in feet or meters and commonly used in two- or three-piece configurations that are either foldable or sliding. The rod's sole has a metal plate for durability, with a zero mark at the bottom. 
The commonly used levels for accurate leveling are automatic levels and electronic digital levels. The automatic level employs a suspended compensator to orient the line of sight automatically once the instrument is roughly leveled using leveling screws and a circular spirit level. An electronic digital level functions as an automatic level with a pendulum compensator for normal optical leveling. In electronic mode, it processes images of the bar-code rod to measure distances. The one-button operation stores the rod reading and distance measurement and computes the point elevation. Sometimes, laser levels, tilting levels, total stations, and transit theodolites are used as levels.