When do you adopt tachometric survey

The formula for the horizontal distance, for the tacheometer with the additive constant 0. Thus, after computing the vertical distance value, the reduced level of instrument station R. L , the height of the instrument H. I , central wire reading R and the R. L of any point under observation can be calculated as:. It means that; the ratio of the distance of the base from the apex and the length of the base is always constant. A tacheometer is a type of theodolite that is used in tacheometric surveying.

It is similar to a transit theodolite fitted with central cross-hairs and additional stadia hairs. The vertical circle of a tacheometer is generally more refined than that of an ordinary theodolite. Also, the telescope fitted in a tacheometer is longer and has a higher power of magnification. The fitted object-glass is also of greater diameter.

The multiplying constant of the instrument is generally taken as The stadia method of tacheometry is a common method adopted for determining the horizontal distance and vertical elevation.

Heliotrope List-II: 1. To determine the horizontal distance 2. To measure the angular distance 3. To establish right angles 4. To determine the difference in elevation between the points 5. To mark the positions of participants in a land survey. The method of tacheometry commonly used is:. The intercept of a staff:.

Stadia tacheometry is based on the principle that. The multiplying constant in the distance formula by tacheometry is given by. Suggested Test Series. Suggested Exams. More Surveying Questions Q1. Match the lists and select the correct option. The staff readings taken are given below. A tachometer is essentially nothing more than a theodolite fitted with stadia hairs , is generally used for tacheometric surveying.

The stadia diaphragm of the tachometer has two hairs, one is above, and the other is below the horizontal crosshair at equal distance. For short distances say up to meters ordinary leveling staves may be used. For greater distances, the stadia rods 3 to 5 meters in length, are generally used. In this method, stadia hairs are kept at a fixed interval and the intercept on the leveling staff or stadia rod varies, depending upon the horizontal distance between the instrument station and the staff.

When the staff rod intercept is more than the length of the staff, then only half an intercept is read, which must be equal to the difference between central stadia hair reading and the lower or upper stadia hair reading. In this method, the intercept of the leveling staff is kept constant and the distances between the stadia hairs are variable.

In this case, a provision is made for the measurement of the variable interval between the stadia hairs. The stadia hairs are not used, in this method. Readings on staff are taken against the horizontal crosshair.