Wednesday, January 1, 2014

Surveying notes for GATE, PSUs - Part 6

Hello there,
How have you been? Here is 6th part of one liners for the preparation of the GATE and PSUs.

  • In Levelling, a station is the point where the levelling staff is held and not where level is set up.
  • The inner surface of a bubble tube is an arc of a circle.
  • Sensitivity of a level tube can be increased by the increase in length of bubble.
  • Dumply level is most suitable when a numbers of readings are to be taken from single setting of the instrument.
  • The difference of levels between two stations A and B is to be determined. For best results, the instrument station should be equidistant from A and B.
  • contour interval is inversely proportional to the scale of the map.
  • An imaginary line lying throughout the surface of ground and preserving a constant inclination to the horizontal is known as contour gradient.
  • Two contours of different elevations do not cross each other except in case of an overhanging cliff.
  • A series of closely spaced contour lines represents a steep slope.
  • Direct method of contouring is most accurate method.
  • In direct method of contouring, the process of locating or identifying points lying on a contour is called vertical control.
  • In the cross section method of indirect contouring, the spacing of cross-sections depends upon contour interval, scale of plan and characteristics of ground.
  • For hilly terrains Tacheometric method of contouring is most suitable.
  • contour interval for any map is kept constant.
  • Closed contours, with higher values inside represents a hillock.
  • Benchmark is established by spirit leveling.
  • Plane table is the type of survey which requires least office work.
  • Intersection method of detailed plotting is most suitable for hilly areas where the points are not accessible.
  • Detailed plotting is generally done by radiation method.
  • Three point problem can be solved by Tracing paper method, Bessels method and Lehman's method.
  • The size of a plane table is 600 mm * 750 mm.
  • The process of determining the locations of the instrument station by drawing resectors from the  locations of the known stations is called resection
  • Plumbing fork is used for accurate centering of plane table.
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