PRINCIPLE OF SURVEYING

 

PRINCIPLE  OF SURVEYING

The principles of surveying are, 

1.     Location of a point by Measurement from two point of reference

The relative positions of the points to be surveyed should be located by measurement from at least two points of reference, the positions of which have already been fixed Let  C and D be the reference points on the ground. The ground the distance CD can be measured accurately and the relatives positions of C and D can be Plotted on the sheet to some scale. The points C and D will thus served as reference points for fixing the relative position of other points. any other point, A can be located by any of the following direct method.

a)      Distance CA and DA can be measured and point A can be plotted by drawing the two arcs to the same scale to which CD has been plotted. This principle is very much used in chain surveying.

b)      A perpendicular AB can be Draw on the reference line CD and length CB and AB are measured. The Point A can then be plotted using set square. This principle is used for locating details.

c)      The distance DA and the angle CDA can be measured and point A is plotted by means of a protractor. This principle is used in traversing.

d)      In this method, The distance CA and DA are not measured but angle ACD and angle ADC are measured with an angle-measuring instrument. Point A is plotted by means of a protractor. This principle is very much used in triangulation and the method used for very extensive work.

e)      Angle ADC and distance CA are measured and point A is plotted drawing an angle and swinging an arc from C. This principle, used in traversing, is of minor utility.

2.      To work from whole to the Part

Under this principle, fix first a system of control points with great precision of the whole area to be surveyed. Then the whole area will be divided into large triangles or large traverses or both.

            minor control points can then be established by less precise methods and the details can be located using these minor control points by running minor traverses etc. The idea of working in this way is to prevent the accumulation of errors.

            If we work from part to the whole, small errors will increase in the process of of expansion of survey and will become un-controllable at the end.