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RAFT FOUNDATION IS A  thick concrete slab resting on a large area of soil/surface reinforced with steel, supporting column or wall and transfer its  loads from the structure to  soil. it is generally used to support structures like residential or commercial buildings, hostel/schools  where soil condition is poor, storage tanks, silos, foundations for heavy industrial equipment etc. it is very important type of foundation in modern ways of construction.

A surveyor instrument having a short telescope fixed rigidtly to a horizontal rotating table.

A theodolite   is a precision instrument for measuring angles   in the horizontal and vertical planes. Theodolites are mainly used for  surveying  applications, and have been adapted for specialized purposes in fields like metrology . A modern theodolite consists of a movable telescope mounted within two perpendicular axes — the horizontal  or trunnion  axis , and the vertical axis. When the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision, typically to seconds of arc.

The  following two basic principles should be considered while determining relative position of points on the surface of earth:- 1. determining suitable method for locating a point:- it is  always practicable to select two points in the field to measure the distance between them. These can be represented on paper by two points placed in a convenient positions. 2.working from whole to the part:- in surveying an area, it is essential to establish first of all a system of control points with great precision. Minor control points can then be established by less precise method and the details can be located  afterwards by method of triangulation or traversing between control points.  Know the basic and you will never need to know again and again.

IT  is a branch of survey which helps in determination of elevation of a given point or object with espect to some specified point or object. . Common levelling instruments include the spirit level , the dumpy level , the digital level, and the laser level. The dumpy level is an older style of optical instrument. It is commonly believed that dumpy levelling is less accurate than other types of levelling, but such is not the case. Dumpy levelling requires shorter and therefore more numerous sights,   but this fault is compensated by the practice of making foresights and backsights equal.