Thursday, January 2, 2014

Surveying notes for GATE, PSUs - Part 7

Hello there,
How have you been? Here is 7th part of one liners for the preparation of the GATE and PSUs.
  • Two point problem and three problems are methods of orientation and resection.
  • Resection by two point problem requires more labor than by three point problem.
  • Methods used to locate the plane table station are resection and traversing.
  • After fixing the plane table to the tripod, the main operations which are needed at each plane table station are levelling, centering and orientation respectively.
  • Bowditch rule is applied to a closed traverse for adjustment of closing error.
  • If in a closed traverse, sum of south latitudes is more than sum of north latitudes and also sum of east departures is more than west departures, the bearing of closing line is in NW quadrant.
  • The angle between prolongation of preceding line and the forward line of a traverse is called deflection angle.
  • Transit rule of adjusting the consecutive co-ordinates of a traverse is used where angular measurements are more accurate than linear measurements.
  • While theodolite traversing, angles are measured from at least two stations to locate a  point which is at a far distance.
  • Subtense bar is an instrument used fr measurement of horizontal distances in undulated areas.
  • Horizontal distances obtained by tacheometric observations do not require slope and tension corrections.
  • There are three horizontal corss hairs- in a stadia diaphragms.
  • In movable hair method, the intercept on leveling staff is kept constant and stadia hair interval is variable.
  • In fixed hair method the intercept on leveling staff is variable and stadia hair interval is fixed.
  • In tangential hair method the stadia hairs are not used.
  • The angle subtended by the long chord of a simple circular curve at its centre is equal to angle of deflection.
All information is learned through books and practical exercises.

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