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6.4 Sources of Errors in Stadia Work
Errors that occur in stadia work are both instrumental and personal, and include
the following:
6.4.1 Instrumental Errors
1. Improper spacing of stadia wires
2. Index error in vertical or zenith angles
3. Incorrect length of rod graduations
4. Line of sight not established truly horizontal by level vials
6.4.2 Personal Errors
1. Rod not held plumb (avoid by using a rod level)
2. Incorrect rod reading resulting from long sights
3. Careless leveling for vertical-arc readings
4. Mistakes:
a) Mistakes in reading the rod intercept
b) Use of an incorrect stadia interval factor
c) Waving the rod
d) Index error applied with wrong sign
e) Confusion of plus and minus vertical angles read with a transit.

Exercise

1. The tacheometric observations in table below were taken along the line of a
proposed roadway at approximately 20m intervals.

Calculate, the reduced level and true chainage for each station.

2. In determining the elevation of point A and the distance between two points,
A and B, a theodolite is set up at A and the following data are obtained:
0
Z=92 45’,stadia interval = 1.311m, hi = 1.28m, and the line of sight at 2.62m on
rod. The instrument constant K=100 and C=0. The elevation of B is 38.28m.
Compute the distance AB and elevation of point A.

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