Stadia Tacheometry determination of

tacheometric constants

tacheometric constants

Aim :

To determine the Tacheometric constants.

Instruments required :

Tacheometer with stand, Levelling Staff, Ranging rods, tape

General :

An ordinary transit theodolite fitted with stadia hair is known as Tacheometer. This method completely eliminated the use of tape or chain and is very rapid and convenient..

Procedure :

1. Set up the instrument at A.

2. Measure a line AB, 30 metres long on a fairly level ground and fix arrows at 10m intervals.

3. Note down the stadia hair readings (top,middle, bottom), by placing the staff over the arrow stations (PQR)

4. Keep the vertical circle to read zero during observations.

5. Calculate the other staff intercepts in the same manner.

Calculation:

Stadia intercept : S = Difference of top and bottom hair readings

Let S

_{1}, is the staff intercept corresponding to distance D_{1}and S_{2}corresponding to D_{2}. By using tachometric equation. D = S + (f+d), since vertical angle is zero.

where = Multiplying constant denoted by C.

and (f+d) = Additive constant denoted by K.

Then D = CS + K

Now we have,

D

_{1}= CS1 + K D

_{2}= CS2 + K Solving the above two equations to get the values for C and K.

Similarly find out the values for C and K by other set of readings.

The average values of the C and K, will be the Tacheometric Constants.

Result :

Tacheometric additive constant K =

Tacheometric Multiplying Constant C =

TACHEOMETRIC CONSTANTS

Inst. at | Staff station | Horizontal distance | Stadia hair readings | Stadia intercept | ||

Top | Middle | Bottom | ||||

A | P | 10m | | | | |

| G | 10m | | | | |

| R | 10m | | | | |

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