### Various terms used in Surveying

1. Plan and Map: Plan and map are the representation of the area on the paper. The plan is the representation of the smaller area as compared to the larger area in case of the map.  You can read and see the maps of India but you will not see the plan of the India, because we use the term map for it.
2.Bearing:  The term bearing is the horizontal angle which a given line makes with the reference line/direction(generally    magnetic north is taken as the reference line).  The bearing are of many type. According to the direction of work it is for-bearing and back-bearing. There are two system of use for it, it is whole circle bearing(W.C.B.) system and quadrantal bearing system(Q.B.S.). The bearing is further classified as Fore Bearing(F.B.) and Back Bearing(B.B.).
3. Elevation: Elevation is the vertical distance of the given point from the assumed or given datum. The datum generally taken is the mean sea level(M.S.L.), so it is taken as the 0m.
4. Levelling: The branch of surveying in which we determine the elevation of a given point or we locate a point at the given elevations.
5. Contours: Contours are the imaginary lines on the surface of the earth, which join the points of the same or constant elevations.
6. Temporary adjustments: Temporary adjustments of any surveying instrument are the adjustments of the instrument which are done at every instrument station after we change the location of the instrument.
7. Topography map: A topography map is prepared to know the topography of the area to be mapped, so it shows the horizontal as well as the vertical distances between two points in a map. You can interpret the hills, reservoirs, depressions, ridges, valleys, forests, roads, bridges and all the details using a topographic map. Topographic map is used in the early stages of planning the big projects like road construction, railways construction, canal construction, dam construction and almost any important construction project.
8. Tacheometer: Tacheometer is a surveying instrument used to find the horizontal and the vertical distances between the two points, by using the angular observations only. You don't need a chain or a tape if you have a tacheometer.  It is similar to a Theodolite but fixed with a stadia diaphragm.