2) Instrumentation

2) Instrumentation

1. Total Sation

   • Obtains horizontal & vertical angles and horizontal distance
   • Conditions
     • H┴V
     • Z┴T
     • T┴V
     • H║T
   • Possible errors
     • Plate Bubble Error
       • Adjustment: remove half of the deviation using the foot screws, other half using level adjusting screws
         • Turn the theodolite 90° to be in line with the 3rd foot screw, adjust full error
           • Rotate by 360° as check
     • Collimation axis error
       • CL and CR reading of the same point should differ by 180°
         • If not: sight point A on CL and place a peg at that position
           • Sight same point on CR and place a peg
             • Angle between the two pegs describes 4 times the error
               • While sighting A(CR) move the cross hairs to 1/4 the distance of A(CR) to A(CL)
     • Trunnion axis error
       • Sight point A in CL (A must have vertical angle higher than 30°)
         • Lower the telescope and place a peg at A(CL) (instrument being 50m away)
           • Repeat and place a peg at A(CR)
             • Place a peg midway without changing the horizontal circle
               • Raise the telescope to A, if the cross hairs do not intersect with A there is an error present
     • Verticallity/Horizontality of cross hairs
       • verticality check
         • Point to a steady line, if the reticals vertica line is inclined it has to be adjusted
       • Horizontality check
         • Point to a fine mark and move the telescope sideways, the mark should not deviate from the line

2. Level

   • Used to obtain height differences between different points and the geoid
   • Represented to the mm
   • Errors eliminated by 2 peg test
   • Reference surface: Geoid
     • Approximates MSL
   • Rise and Fall Method
   • Height of collimination

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