What is tacheometry in survey?
What is tacheometry in survey?
Tacheometry (/ˌtækiˈɒmɪtri/; from Greek for “quick measure”) is a system of rapid surveying, by which the horizontal and vertical positions of points on the earth’s surface relative to one another are determined without using a chain or tape, or a separate levelling instrument.
What is the formula for the use of stadia lines?
If one observes a vertical length on a stadia rod, rule or levelling rod with the telescope and sees that the rod spans 0.500 m between the marks (the stadia interval), then the horizontal distance from the instrument to the rod is: 0.500m x 100 = 50 m.
What is tangential method?
Tangential Method. The tangential method of tacheometry is being used when stadia hairs are not present in the diaphragm of the instrument or when the staff is too far to read. In this method, the staff sighted is fitted with two big targets (or vanes) spaced at a fixed vertical distances.
How do you find the Tacheometric constant?
These can be computed from field observation by adopting following procedure.
- Step 1 : Set up the tacheometer at any station say P on a flat ground.
- Step 2 : Select another point say Q about 200 m away.
- Step 3 : Keep the staff on the peg-1, and obtain the staff intercept say s1 .
What is the basic principle of Tacheometry?
Principle of Tacheometric Surveying The principle of tacheometric surveying is based on the property of an isosceles triangle. It means that; the ratio of the distance of the base from the apex and the length of the base is always constant.
Which instrument is used for Technometry survey?
Tacheometric is a branch of surveying in which horizontal and vertical distances are determined by taking angular observation with an instrument known as a tachometer. Tacheometric surveying is adopted in rough in rough and difficult terrain where direct leveling and chaining are either not possible or very tedious.
How do you calculate dumpy level?
The formula to calculate height using a dumpy level is: Benchmark height + backsight measurement – foresight measurement.
How many hairs are present in stadia?
Explanation: The stadia diaphragm has three horizontal hairs viz., a central horizontal hair and upper and lower stadia hairs. The upper and lower stadia hairs are equidistant from the central horizontal hair. Stadia hairs are sometimes called stadia lines. 8.
What is Subtense method in Tacheometric surveying?
Subtense Method This method is similar to the fixed hair method except that the stadia interval is variable. Suitable arrangement is made to vary the distance between the stadia hair as to set them against the two targets on the staff kept at the point under observation.
In which method the distance between stadia hair is fixed?
Welcome back.
| Sr.no | Fixed hair |
|---|---|
| 1 | In this method interval between two stadia hair is fixed. |
| 2 | In this method horizontal distance from the instrument to the staff can be determine from the value of staff intercept intercepted by the stadia line. |
| 3 | Staff intercept varies with the distance at which the staff is held. |
What is fixed hair method?
Fixed Hair Method: In the fixed hair method of tacheometric surveying, the instrument employed for taking observations consist of a telescope fitted with two additional horizontal cross hairs one above and the other below the central hair. These are placed equidistant from the central hair and are called stadia hairs.
What is stadia method in surveying?
: a surveying method for determination of distances and differences of elevation by means of a telescopic instrument having two horizontal lines through which the marks on a graduated rod are observed also : the instrument or rod.
Which is an example of the defination of tachymetry?
DEFINATION OF TACHYMETRY The word tachymetry is derived from the Greek takhus metron meaning ‘swift measurement’. It is a branch of surveying where height and distances between ground marks are obtained by optical means only. An example of tachymetry method is the stadia method. The distance between marks can be obtained without using a tape.
What are the methods of surveying in tacheometry?
The Stadia System of Tacheometry: In the stadia system of tacheometry there are two methods of surveying viz: (i) Fixed hair method, and (ii) Moveable hair method.
How is the vertical distance of a tacheometer calculated?
This is marked with heights from the base or foot, and is graduated according to the form of tacheometer in use. The horizontal distance is inferred from the vertical angle included between two well-defined points on the staff and the known vertical distance between them.
When to use multiplicative constants in tacheometry?
If the stadia rod is not at the same elevation as the instrument, the value must be corrected for the angle of elevation between the instrument and the rod. The formula most widely used for finding the distances is: are multiplicative and additive constants. Generally, the instrument is made so that exactly, to simplify calculations.
