Tacheometry

TACHEOMETRY

Unit 1

Tacheometry

• Defined as a procedure of 

obtaining horizontal distances 

and differences in elevation 

based on the optical geometry 

of the instrument employed

of the instrument employed

• compared to taping and 

differential leveling, the 

g,

distances and elevations 

obtained by tacheometric 

methods are usually of a lower 

methods are usually of a lower

degree of accuracy

Uses of Tacheometric Methods

Uses of Tacheometric Methods

• Check the more accurate taped distances to uncover 

p

errors or mistakes

• Determine differences of elevation between points

• Carry lines of levels where low order accuracy is 

required

• M

Measure the lengths of traverse lines

th l th f t

li

• Compile planimetric and topographic maps

• Complete field survey for photographic map

Complete field survey for photographic map

• Locate details for hydrographic survey

THE STADIA METHOD

THE STADIA METHOD

• this method employs 

p y

the sighting telescope 

of an instrument in 

reading a small angle 

reading a small angle

along a vertical plane 

and in determining the 

g

length which the angle 

subtends on a 

graduated rod held 

graduated rod held

vertical on the distant 

point

• the word stadia denoted

600 Greek units, or 184

m 93 cm (606 ft 9 in) by

present-day international

standards

THE STADIA METHOD

the term is now applied to the cross hairs and

rod used in making measurements, as well as to

the method itself

the equipment for stadia measurements

consists of a telescope with two horizontal hairs

called stadia hairs and a graduated rod called a

stadia rod

y p y y

distances can be measured very rapidly by the

stadia method

THE STADIA METHOD

PRINCIPLE OF THE STADIA

Since ab is equal to a’b’, by similar triangles

q

y

g

f/i = d/s

And

d = (f/i)s

also

D = d + (f + c)

D = (f/i)s + C

D = Ks + C

STADIA CONSTANTS

the stadia constant, the distance from the center of

p

p

the...