FAQ: What Are Tacheometric Constants?

What is additive constant?

The additive constant c is the sum of focal length of the object lens and distance from the center of the object lens to the center of the instrument.

What are the systems of Tacheometric measurements?

Different systems of Tacheometric Measurement: The various systems of tacheometric survey may be classified as follows:  The stadia System (a) Fixed Hair method of Stadia method (b) Movable hair method, or Subtense method  The tangential system  Measurements by means of special instruments The principle common to

What is the basis for Tacheometric 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 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.

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What is the value of additive constant in an electric lens?

What is the value of additive constant in anallactic lens? Explanation: If the anallactic lens has been provided in the internal focussing telescope, the additive constant can be reduced to minimal value i.e., zero due to which the computations can be make quicker.

What is multiplying constant?

The constant, used in stadia work, by which the staff intercept is multiplied to determine the distance between the staff and the theodolite. The value is generally taken as 100.

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.

What is the principle of Tacheometry?

The main principle of Tacheometry is based on the basic principle of isosceles triangle. In any two side equal triangle means isoceles triangle, there is one property which is used in the Tacheometry. Ratio of the perpendicular to vertex on their base and their base is always constant in isoceles triangle.

What is fixed hair method?

Fixed Hair Method: In the fixed hair method the cross hairs of the diaphragm are kept at a constant distance apart and the staff intercept varies with the horizontal and vertical position of the staff with respect to the Theodolite.

What are the advantages of Tacheometric surveying?

Advantages of Tacheometric Surveying It is one of the fastest methods of surveying. The accuracy of tacheometric surveying in uneven or difficult terrain is quite satisfactory. Does not require any tedious jobs with tapes and chains. Cost efficient with relative to time.

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Which method of Tacheometry is most common in use?

As in the field of tacheometric surveying ‘Stadia Method ‘ is the most widely used procedure so we will discuss the principle behind it. The stadia method follows the principle that in similar isosceles triangles the ratio of the perpendicular to the base is constant.

What is the least count of stadia rod?

For small distances ( up to 100 meters) a level staff may be used for tacheometric surveying. But for greater distances stadia rod is needed. Stadia rod is of one piece having 3 to 5 meters length. The smallest subdivision is usually 5 mm.

How do you calculate Tacheometry?

2. Additive constant B=(f+d) where, f=focal length of the lens d= horizontal distance between instrument axis to optical centre of a lens The value of additive constant. varies from 0.15 m to 0.60 m.

How many horizontal hairs are there in Tacheometer?

Explanation: A tacheometer is similar to an ordinary transit theodolite, generally a vernier theodolite itself, fitted with two stadia wires in addition to the central cross-hair. The stadia diaphragm has three horizontal hairs viz., a central horizontal hair and upper and lower stadia hairs.

What is the least count of Levelling staff?

Staff are either solid (having single piece of 3 meter height) (Figure 11.5) or folding staff (of 4 meter height into two or three pieces) (Figure 11.6). The least count of a leveling staff is 5 mm.

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