Various terms are used in leveling which must be understood clearly before starting surveying. Leveling is conducted in the field to know the elevation difference between two points. To find the elevation difference, at least the elevation of one point must be known. What if the elevations are not known or how to proceed with leveling with unknown elevation points? It is not a big task if basic terms of leveling are known. So, one must know these basic terms before studying the art of leveling. Terms Used in Leveling The general terms used in leveling are: Vertical line Horizontal line Level surface Datum Benchmark Mean sea level Reduced level Vertical Line It is the line which is indicated by plumb at required station. So, this is also called as plumb line. It’s just decided based on the consideration of earth’s gravity. Vertical line connects the station point to the center of the earth. A plumb is released from the instrument height with the help of threa...