Definition of Surveying
The different methods of finding out the alternative and relative position of distinctive features on the earth surface or just beneath the top surface of earth level, i.e measurements of distances, any directions and elevations is may be expressed as surveying.
Different sections of surveying
Surveying may be classified as into two different divisions.
- Plane Surveying – In this surveying process earth surface is considered or assumed to be as a plane surface and curvature of the earth surface has been ignored .
- Geodetic surveying – In this survey process the curvature of the earth has been considered and for more prominent result linear and angular observations has been taken into the account.MeridianIt may be defined as fixed direction on the earth surface, with reference to th bearings of survey lines are compared and expressed.
- True Meridian – The true or geographical meridian are generally passing through a place is the line of intersection of the earth surface by a plane which contains North and South poles and also the given place
- Magnetic Meridian – The geometrical longitudinal axis of freely suspended and properly balanced magnetic needle , which is unaffected by local attractive forces , defines the Magnetic Meridian.
Isogonic Lines – It is an imaginary lines joining the places of equal declination either positive or negative sides , on the surface of the earth , are called Isogonic lines.
Magnetic Declination – The horizontal angle between the true north and magnetic north at the time of observation is called Magnetic Declination. Depending upon the position of the magnetic meridian, magnetic declination may be East or West of true meridian.
Bearings – The horizontal angle between the meridian and the survey line , measured in clockwise direction , is called bearing.
Bearings may be classified in two types,
- Whole Circle Bearing – In the whole circle bearing a line is calculated from the given meridian in the clockwise direction by using the whole circle of graduations. It may be vary from 0o to 360o.
- The Quadrantal Bearing – In this bearings a line is measured in the eastward or west ward from the north and south of the meridian whichever is nearer. The quadrant in which the line is mentioned, to specify the locations of the line. This bearings few time called reduced bearings.