TACHEOMETRY | Useful situation of Tacheometric survey | Characteristics of tachometric survey | Instrument used in tacheometry | Principle of tacheometry |

Tacheometry

Tacheometry or elementary is a branch of serving in which the horizontal distances and the difference of elevations of points are determined by an instrument.

The instrument used for technometry is known as tacheometer.

The method of tacheometric Surveying is also known as optical distance measuring (O.D.M) method because and optical instrument (tacheimeter) is used.

Useful situation of Tacheometric survey

When ground surface is an event it is difficult to lay chain take on the ground.

When obstackle such a steep and broken ground deep Valley exactra

This method is convenient for service of road Kurnool Railway etc.

When area to be served is a very large

Characteristics of tachometric survey

Horizontal and vertical angle can be measured with the help of tacheometer

Horizontal distance and vertical distance between two points are directly measured

For tacheometric survey onley Tak u m and a study abroad are required

Chain or tape not required

Purpose of tacheometric surveying

To prepare contour map

To prepare topographic map

To fix alignment of road railway Canal etc

Useful for hydrographic surveying

To carry out survey with speed but accuracy is less

Also useful for checking out the distance measured by chain or tape or checking the elevation determined by level

Instrument used in tacheometry 

Normally to instrumental are used for tacheometry

Tacheometer 

Levelling staff or Stadia Road

Characteristics of tacheometer 

The multiplying constant for tacheometer is f/i  100

The Tech you metre telescope analytic lens is fitted and additive constant is f + d is 0.

The telescope should be powerful having a magnification of 20-30 times of diameter. 

Diaper should be a great magnifying power than usual so that it is possible to obtain a clear a staff reading from a long distance

Various pattern of stadia diaphragm

Principle of tacheometry.

The principle of tacheometry is based on the property of isosceles triangle where the ratio of the distance of the base from the apex and the length of the base is always constant.

As shown in fig:-
     
△O1 a1 a2, △O2 b1 b2, △O1 c1 c2
D1, D2 and D3 are distance from apex to base.

S1, S2 ans S3 are bases ( staff intercept )

D1/S1 = D2/S2 = D3/S3 = f/I = constant.

f/i = multiplying constant

f = focal length
i = Stadia interval.