Surveying 665


Surveying is the art of making measurements of the relative positions of natural and man made features on earth surface and plotting this measurement to suitable scale to form a map plan or section.

PRIMARY DIVISION OF SURVEYING

  1. Geodetic surveying – this is the type of survey in which curvature of the earth is taken into account including know how of spherical geometry.
  2. Plane surveying –  this is the type of survey in which area under consideration is taken to be a horizontal plane and measurements plotted will represent projection on horizontal plane on the actual field measurements.

CLASSIFICATION OF SURVEYING

a) classification based upon the nature of field survey :-

  • Land surveying – it includes
  1. Topographic surveying – this is the survey for the main natural or artificial features i.e hills, lakes, valleys, villages.
  2. Cadastral surveying – surveys for the preparation of plans showing, detailing legal property boundary such as land.
  3. City surveying – this is survey related to streets, sewers and other works.
  • Marine / hydrographical surveying – These deals with bodies of water with purpose of navigation on water, harbor or sea level
  • Astronomical Survey – it offers the surveyor means of obtaining the absolute and direction of any line on surface of the earth. it may involve observation of the sun and stars

b) classification based on objective of survey

  • Engineering survey – These are undertaken for determination of qualities in order to obtain sufficient data for designing engineering works.
  • Military surveying – used in determining points of strategic importance
  • Mine surveying – this is used for exploring minerals
  • Geological survey – used in determining different struts in earths crust
  • Archeological survey – used for unearthing relics of antiquity.

c) Classification based on instruments used :-

  • Chain surveying
  • Onright surveying
  • Transverse surveying
  • Triangulation surveying
  • Archeometric surveying
  • Plain table surveying
  • Photographic surveying
  • Aerial surveying

SURVEYING METHODS

  1. Triangulation – consists of a framework of triangles in which all angles measured but only one side measured. The remaining sides are realized by solving triangles using sine rule.
  2. Tri-lateration – all sides length of framework of triangles are measured.
  3. Transverse – its a chain of straight lines connected at their ends. The length of each line and angles between successive lines are measured.
  4. Radiation – The position of a point is fixed by an observed direction in azimuth (compass direction) and measured distance.
  5. off-setting– position of a point is fixed by measurement of a distance at a right angle to control a length.

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