Tag Archive for Tag: Levelling

Tag: Levelling Levelling

Levelling is the process of finding the height of a new point or points by comparison with that of an existing point which has been selected as a datum or whose height is already known with respect to some other datum. If the points are close to each other and only their relative heights are needed, the simplest procedure is

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Tag: Levelling Levelling

For most site survey work tilting or automatic levels provide for quick and accurate results. As with all instruments, they should be checked regularly for accuracy and returned to the manufacturer for overhaul and re-setting at intervals. The levelling staff must be kept clean and its markings clear to reduce reading errors and it is worth spending time to ensure the chainman is clear as

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Tag: Levelling Types of Direct Levelling

The following are the different types of direct levelling: (i) Simple levelling (ii) Differential levelling (iii) Fly levelling (iv) Profile levelling (v) Cross sectioning and (vi) Reciprocal levelling. Simple Levelling It is the method used for finding difference between the levels of two nearby points. Figure 15.6 shows one such case in which level of A is assumed, say 200.00

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Tag: Levelling Terms Used in Direct Method of Levelling

The following terms are used in direct method of levelling: (i) Plane of Collimation: It is the reduced level of plane of sight with respect to the datum selected. It is also known as ‘height of instrument’. It should not be confused with the height of telescope from the ground where the instrument is set. (ii) Back Sight (BS): It

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Tag: Levelling Methods of Levelling

The following methods are used to determine the difference in elevation of various points: (i) Barometric levelling (ii) Hypsometric levelling (iii) Direct levelling and (iv) Indirect levelling. Barometric Levelling This method depends on the principle that atmospheric pressure depends upon the elevation of place. Barometer is used to measure the atmospheric pressure and hence elevation is computed. However it is

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Tag: Levelling Levelling Staff

Along with a level, a levelling staff is also required for levelling. The levelling staff is a rectangular rod having graduations. The staff is provided with a metal shoes at its bottom to resist wear and tear. The foot of the shoe represents zero reading. Levelling staff may be divided into two groups: (i) Self reading staff (ii) Target staff.

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Tag: Levelling Terms Used in Levelling

Before studying the art of levelling, it is necessary to clearly understand the following terms used in levelling: 1. Level Surface: A surface parallel to the mean spheroid of the earth is called a level surface and the line drawn on the level surface is known as a level line. Hence all points lying on a level surface are equidistant

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Tag: Levelling Object and Uses of Levelling

As stated in the definition of levelling, the object is (i) to determine the elevations of given points with respect to a datum (ii) to establish the points of required height above or below the datum line. Uses of levelling are (i) to determine or to set the plinth level of a building. (ii) to decide or set the road,

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Tag: Levelling Working Operations

After fixing the table top to the stand and drawing sheet to the table, the following operations are to be carried out before map making: 1. Centering 2. Levelling 3. Orientation. 14.2.1 Centering Centering is the process of setting the plane table on the point so that its plotted position is exactly over the position on the ground. This is achieved

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