What are the different types of Level in Civil Engineering Survey
LEVELLING * Levelling is the art of determining the elevations of the given point above or below a datum line or establishing given points of required heights above or below the datum line. * The point or the surface with respect to which levels of other points or planes are calculated is called datum or datum surface. * Mean sea level (MSL) is the average sea level for all stages of the tides which is established after observing tides for a long period of 19 years. In India MSL is the level established at Karachi, presently in Pakistan. * The levels of various points taken as height above the datum surface are known as reduced levels (RL). * Benchmark is a relatively permanent point of reference whose elevation with respect to some assumed datum is known. There are four types of bench marks; namely, GTS (Great Trignometric Survey) benchmarks, permanent benchmarks, arbitrary benchmarks and temporary benchmarks. * Methods of levelling employed are: 1. Direct levelling (spirit levelling)...