Temporary adjustment

Adjustment of level :

Adjustments made at each setting of the instrument before taking observations are known as temporary adjustments.

Temporary Adjustments : includes

  • Setting up the level
  • Levelling up
  • Elimination of parallax
  1. Setting up the level : This operation includes fixing the instrument on the tripod and also approximate levelling by leg adjustment.

  2. Levelling up : Accurate levelling is done with the help of foot screws and by using plate levels. The object of levelling up the instrument is to make its vertical axis truly vertical.

  3. Elimination of parallax : If the image formed by the objective does not lie in the plane of the cross hairs, there will be a shift in the image due to shift of the eye. Such displacement of image is termed as parallax. Parallax is removed in two stages.

  • Focusing the eye for distinct vision of cross hairs.
  • Focusing the objective so that image is formed in the plane of cross hairs

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