7/24/2019 Tacheometry Discussion

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DISCUSSION

1) Tachometry also has the same errors like weve done in traversing. There are four

specific sources of errors needed to be emphasized in tachometry observations. They

are staff readings and tilt of the pole or staff. Observer tends to make wrong

observation when observing the staff reading, they might misread the staff marking

scales and this brought to the crucial error along the booking process. esides, the

tilting of the staff rod can influence the accuracy of the height readings taken from the

staff. !hen the staff is not truly vertical"#$) or almost to it, the reading taken is

incorrect and lead to the failure of tachometry process.

%) esides, the errors encountered during tachometry also can be derived from

instrumental errors. They are those caused by the ad&ustment of the instruments used

or faults in them. 'ny errors in these measurements have serious implications in the

heights and distances measured with the instruments. To avoid such errors, thefollowing points should be taken care of(

a) The tachometer should be in perfect ad&ustment for taking observation.

b) The altitude bubble should be at the centre of its run while reading the vertical

circle for angles. 'ny inde error should be detected and eliminated or accounted

for.

c) The multiplying and additive constants of the instrument should be periodically

checked to see that they indeed have the values that are being used.

d) The stadia rod "staff) should be accurately divided into parts. The graduations

should be uniform and free of errors. They should be marked bold for greatervisibility from a large distance.

*) Others errors due to manipulation and sighting are inaccurate levelling of the

instrument, inaccurate reading of horizontal line and vertical angles, poor focusing

errors, inaccurate bisection of the target, inaccurate reading of the staff intercept and

lastly due to errors in holding the staff.

4) +rrors in conducting tachometry survey also caused by natural causes. These include

errors due to high winds. uring high winds, it is difficult to keep the staff verticaland read it accurately. !orks should be undertaken during hot mid-day period. n very

hot conditions, the instrument should be protected with an umbrella to avoid errors

due to the une/ual epansion of different parts of instruments. !ork may also be

hampered by bad visibility due to strong sunlight and glare.