Procedure of levelling:
1.The instrument must be check before use! (see lecture)
2.The instrument and level must be stable settled-up
3.The bubble tube must be leveled before the reading
Beware of sun exposure (will wander)
Ensure the instruments pendulum is in-limit
4.The instrument must be set up in the middle between two staffs
Prevents curvature effects
If impossible, use the same distances, but opposite for the next readings
5.You must not use the parallax screw between the backsight and foresight readings
6.Readings must be taken 30-50 cm above the ground
Surface refractions
Beware also of temperature gradients (inside/outside buildings) !!!!
7.Staff should be set up vertically
8.A change plate should be used
9.Leveling must be done in two opposite directions but the same line (beware of gravity gradients)
10.Staff should be calibrated, especially if INVAR
11,Be careful when crossing rivers (large water surfaces)
Use “same-time” (mutual) observations
Repeat it during different times of the day
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