Methods of Distance Measurement In Surveying

# Methods of Distance Measurement In Surveying

Upendra Kumar

METHOD OF DETERMINING DISTANCE
•The horizontal or linear distance between two points is the distance between the plumb line through the points.
•The cost of making a measurement increase with the desired precision of the work.

There are three main types of horizontal or linear distance measurement.
1. Direct Method.
2. Optical Method.
3. Electronic Method.

1. Direct Method:- This method is most common method for linear measurement. In this method the distance are measured actual on the ground.List of Instrument used for direct measurement.
(i) Passometer:- The passometer is used counting the number of steps automatically by some mechanical device.
(ii) speedometer:- This is used in automobile for recording distance.
(iii) Perambulator:- This instrument a wheel fitted with a fork and handle and shows a distance per revolution.

(iv) Chain:-This is an accurate and common method of measuring distance in this method the distance is measured in the field by chain or tape. A metric chain divided into 100 links is made of galvanized mild steel wire 4mm in diameter. The ends of each link are bent into loops and connected together by means of three oval rings. Which afford flexibility.
2. Optical Method:-In this method, the distance is not measured in the field. It is computed indirectly. The principal of optics is used to determine the distance observations are taken through a telescope fitted with a stadia diaphragm in the transit theodolite.
Optical Method:- Tacheometer
The tachometer is a branch of an angular survey in which the horizontal and vertical distance of points is obtained by instrumental observation. It is the most rapid and less accurate. It is used where the chaining and leveling are difficult and inaccurate.
3.Electronic Method:-Electronic method is more accurate and has high precision. This method is more rapid. Distance is measured with instruments that rely on propagation, reflection, and subsequent reception of either radio or light waves.
Modern E.D.M instruments, basically two types:

i. Electro-optical instruments:- which use light waves measuring distances such as Geodimeter, Makometer, Total station
Total station:-Now days commonly use of measurement of distance, surveying, and leveling. It consists of an EDM electronic theodolite as one unit.it also includes a data collector that automatically collects field data and transfers them to a computer that processes the observed data. It is a high precision instrument.
ii Microwave instruments:-which use radio waves for measurements of distance, such as Electrotape,, Diameter and Micro chain.