To determine the horizontal distances and vertical distances by tacheometric surveying when the line of sight is inclined.

Object: To determine the horizontal distance and vertical distance by tacheometric surveying when the line of sight is inclined.

Equipment:

Digital theodolite, tripod stand, leveling staff, tape, ranging rods, and plum bob.

Theory:

Tacheometric Surveying (Tacheometry):

It is the branch of surveying in which horizontal and vertical distances are determined by taking angular observations and stadia readings with the help of an instrument known as a tacheometer. In this survey, chaining operations are completely eliminated.

Tacheometer:

It is a transit theodolite, fitted with stadia lines (or stadia diaphragm) and an additional convex lens in the telescope of a tacheometer.

Procedure:

Case-I (When staff rod is held vertical)

1. Mark station O.
2. Set the instrument at station O and did the temporary adjustment.
3. Now loosen the horizontal clamp and telescope is directed towards A and bisect the ranging rod at A.
4. Note the V.A. displayed at the display screen.
5. Now hold the staff rod vertically on station A and note the stadia readings, that is, upper stadia, lower stadia,, and central stadia readings.
6. The horizontal distance of OA is calculated by using the distance formula (D = (f/i)scos2θ + (f+d)cosθ).
7. Vertical distance at A is calculated by using the formula (V = ((f/i)sSin2θ)/2 + (f+d)Sinθ).
8. Repeat the above process for vertical distances and horizontal distances of points B, C, D, and E from O.
9. Measure the height of the instrument from the ground with the help of tape.
10. Consider the reduced level of O as 100 feet and calculate the R.Ls of other stations.

Case-II (When staff rod is held perpendicular to the ground)

1. Mark station O.
2. Set the instrument at station O and done the temporary adjustment.
3. Now loosen the horizontal clamp, and the telescope is directed towards A and bisects the ranging rod at A.
4. Note the V.A. displayed at the display screen.
5. Now hold the staff rod perpendicular to the ground on station A and note the stadia readings, that is, upper stadia, lower stadia, and central stadia readings.
6. The horizontal distance of OA is calculated by using the distance formula (D = (f/i)scos2θ + (f+d)cosθ).
7. Vertical distance at A is calculated by using the formula (V = ((f/i)sSin2θ)/2 + (f+d)Sinθ).
8. Repeat the above process for vertical distances and horizontal distances of points B, C, D, and E from O.
9. Measure the height of the instrument from the ground with the help of tape.
10. Consider the reduced level of O as 100 ft and calculate the R.Ls of other stations.

Observations:

Case-I

Instrument Height = …………….

Case-II

Instrument Height = …………….