Distance by Tachymetry (or Tacheometry)

This is another procedure in obtaining horizontal distance. It is based on the optical geometry of the instruments employed and is an indirect method of measurement.

Stadia Method. This method provides a rapid means of determining horizontal distance. The precision of this method depends upon the following factors: refinement with which the instrument was manufactured, the skill of the observer, the length of measurement and the effects of refraction and parallax




Stadia Method

D=Ks + C

Where:

D= the horizontal distance between the instrument and the stadia rod

K=stadia interval factor ( equal to 100 )

s= the difference between the upper and lower stadia readings

C= instrument constant ((approximately equal to 0)


Enrichment Activities:

1. 
   A stadia rod held at a distant point B is sighted by an instrument set up at A. The upper and lower stadia hair readings were observed as 1.300m and 0.900m respectively. If the stadia interval factor (K) is 100 and the instrument constant (C) is zero, detemine the length of line AB.
   

Given: upper stadia reading= 1.300m

lower stadia reading=0.900m

K= 100

s= upper stadia reading – lower stadia reading

s= 1.300m -0.900m

s= 0.40m

D=Ks + C

D= (100)( 0.40m) + 0

1. 
   In walking along a 75-m course, the pacer of a field party counted 43.5, 44, 43.5, 43.75, 44.5, and 43.25 strides. Then 105.5, 106, 105.75 and 106.25 strides were counted in walking from one marker to another established along a straight and level course. Determine the distance between the two markers.
   

2. 
   A student paces a 50m length five times with the following results: 57.00, 56.75, 56.50, 58.00 and 56.25 paces. Determine how many paces must he step off in order to establish a distance of 450 meters on level ground.
   

3. 
   Determine the length of a line negotiated in 208 paces by a person whose pace is 0.76 meters long.
   

4. 
   A farmer walks five times along the width of his parcel of land with the following number of paces: 152, 153, 151,154 and 153 while along its length : 425, 424, 423, 424, and 422. If the pace factor of the farmer is 0.723 m/p, find the area of his land in hectares assuming that the parcel of land is rectangular in shape. (Note 1 hectare=10,000 square meters)
   

5. 
   An instrument was set at a point some distance away from a stadia rod whose upper and lower stadia readings are 1.475m and 0.855m respectively. How far is the instrument to the stadia rod assuming that the instrument constant is 0 and the stadia interval factor is 100?
   

1. 
   Elementary Surveying 3rd edition by Juny Pilapil La Putt
   
2. 
   Surveying by Jack McCormac Et. Al.
   
3. 
   Surveying Theory and Practice By R.E Davis, F. S. Foote
   
4. 
   The principles and Practice of Surveying by C. B. Breed; G.L. Hosmer and A. J. Bone