This is a glossary of levelling terms. Levelling is a surveying method used to find relative height, one use of which is to ensure ground is level during construction, for example, when excavating to prepare for laying a foundation for a house.

Levelling terms

Automatic level A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative height levels of objects or marks. It is ...

– variant of the dumpy level, that makes use of a compensator that ensures that the line of sight remains horizontal once the operator has roughly leveled the instrument. The surveyor sets the instrument up quickly and doesn't have to relevel it carefully each time he sights on a rod on another point. It also reduces the effect of minor settling of the tripod. Three adjustment screws are used to level the instrument. *

Back sight This is a glossary of levelling terms. Levelling is a surveying method used to find relative height, one use of which is to ensure ground is level during construction, for example, when excavating to prepare for laying a foundation for a house. L ...

(BS) – short for "back sight reading", the first staff reading taken by the surveyor after the levelling instrument is set up and levelled. B.S is generally taken on the point of known reduced level as on the benchmark or a change point. *

Benchmark (surveying) The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a "bench" for a leveling rod, thus ensuring that a le ...

– fixed reference point of known elevation with respect to which RL of other points is determined. Benchmarks can be arbitrary or permanent, the former is used for calculation of reduced levels for small survey works and the latter is used to calculate the elevations of significantly important locations and points. Arbitrary benchmarks are assumed to be equal to 100 meters generally and then the elevations with respect to assumed benchmark is determined. It is commonly practiced by engineering students. For GTS surveys of the country, surveyors use permanent benchmarks to calculate the elevations of different points. * Datum surface – reference plane with respect to which RL of the other survey points is determined. The datum surface may be real or imaginary location with a nominated elevation of zero. The commonly used datum is mean sea level.Surveying Volume 1 by Dr. B.C Punmia and Ashok Kumar Jain. Retrieved on 27 October 2014 *

Dumpy level A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative height levels of objects or marks. It i ...

– optical instrument used to establish or check points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and to transfer, measure and set heights. Also called a builder's level or leveling instrument. * Fore sight (FS) – short for "fore sight reading", the last staff reading taken before changing the instrument to the other position. It is the staff reading taken on point whose RL is to determined. This sight is considered as negative and deduced from Height of Instrument to determine RL of the point. * Intermediate sights – all readings taken between back sight and fore sight. These are the points whose RL is determined by the method already mentioned above in FS. Also called inter-sight readings. *

Laser level In surveying and construction, the laser level is a control tool consisting of a rotating laser beam projector that can be affixed to a tripod. The tool is leveled according to the accuracy of the device and projects a fixed red or green beam ...

– control tool consisting of a laser beam projector that can be affixed to a tripod, and which projects a fixed red or green beam along the horizontal and/or vertical axis. A rotary laser level is a more advanced laser level in that it spins the beam of light fast enough to give the effect of a complete 360 degree horizontal or vertical plane, thus illuminating not just a fixed line, but a horizontal plane. *

Levelling Levelling or leveling (American English; American and British English spelling differences#Doubled in British English, see spelling differences) is a branch of surveying, the object of which is to establish or verify or measure the height of sp ...

– measurement of geodetic height using an optical levelling instrument and a level staff or rod having a numbered scale. Common levelling instruments include the spirit level, the dumpy level, the digital level, and the laser level. *

Levelling staff {{short description, Graduated rod used to measure differences between heights A level staff, also called levelling rod, is a graduated wooden or aluminium rod, used with a levelling instrument to determine the difference in height between points ...

– specialized measuring stick or vertical staff used with the dumpy level, held by a second person while the operator of the level looks through it and takes readings off of the staff. Also call a rod. *

Reduced level Reduced level in surveying refers to equating elevations of survey points with reference to a common assumed datum. It is a vertical distance between survey point and adopted datum plane. Thus, it is considered as the base elevation which is used as ...

(RL) – equating elevations of survey points with reference to a common assumed datum. The elevation is positive or negative according as point lies above or below datum. *

Spirit level A spirit level, bubble level, or simply a level, is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other ...

– instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). While used by surveyors, different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, millwrights and other metalworkers, and in some photographic or videographic work.

References

{{reflist Civil engineering Geomatics engineering Levelling Terms Surveying

Levelling terms

See also

References