Tacheometry Discussion

DISCUSSION

1) Tachomet Tachometry ry also has the the same errors like like we’ve done done in traversing. traversing. There 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, esides, the errors errors encountered encountered during during tachom tachometry etry also can can be derived derived from 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 meas ured with the instruments. To avoid such errors, the following points should be taken care of( a) The tachomet tachometer er should should be in in perfect perfect ad&ustment ad&ustment for taking taking observat observation. ion.  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 multiply multiplying ing and additive additive constants constants of the the instrument instrument should should be periodically periodically checked to see that they indeed have the values that are being used. d) The stadia stadia rod "staff) "staff) should should be accurately accurately divided divided into parts. parts. The graduati graduations ons should be uniform and free of errors. They should be marked bold for greater visibility from a large distance.

*) Others errors errors due due to manipulati manipulation on and sighti sighting ng are inaccurate inaccurate levellin levelling g 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 vertical and read it accurately. !orks !orks should be undertaken during hot mid-day period. n ver y hot conditions, the instrument should be protected with an umbrella to avoid errors due to the une/ual epansion of different parts of instruments. !ork !ork may also be hampered by bad visibility due to strong sunlight and glare.