Linear Methods of Surveying | Introduction to Surveying | By Ashutosh Nautiyal

Linear methods of Surveying can be classified into three types:- Direct method Electronic method Optical method Direct method:- The direct method is further divided into five types:- Pacing:- The pacing technique is mostly employed in preliminary surveys and explorations. In this method, the surveyor is required to conduct a rough survey quickly.

Linear Methods of Surveying 







    It can be classified into three types:- 



    • Direct method
     

    • Electronic method

    • Optical method 




    Linear Methods of Surveying | Introduction to Surveying | By Ashutosh Nautiyal
    Linear Methods of Surveying




    Direct method:-



    The direct method is further divided into five types:-


    Pacing:-




    • The pacing technique is mostly employed in preliminary surveys and explorations.


    • In this method, the surveyor is required to conduct a rough survey quickly.

    • It also roughly checks the distance measured by other means.


    • The number of paces between the two points of the line is counted.


    • Knowing the average length of the pace helps to know the length of the line.


    • The length of the pace is dependent on the person who is measuring, the ground, the speed of pacing and the slope of the country.


    • By walking on an approximate level ground over various lines of known lengths helps in determining the length of one's natural step.


    • It is a difficult process to perform pacing over a rough surface or on slopes.


    Passometer:-




    • The passometer is a watch-like instrument that is carried on the person's pocket or tied on the man's leg.


    • This instrument records the paces when the man moves from one point to another.


    • The distance is calculated by multiplying the number of paces by the average length of the pace.


    • This method overcomes the monotony and strain in counting the paces by the surveyor.


    Pedometer:-




    • The pedometer is a device similar to passometer but it is adjusted to the length of the pace of the person carrying it.


    • It registers the total distance covered by any number of paces.



    • It automatically measures the distance.


    • It is best in measuring vertical distances.


    Odometer:-




    • The odometer is an instrument that measures the number of revolutions of a wheel.


    • It is fitted to the wheel that is rolled along the line whose length is required.



    • The distance covered is calculated by multiplying the number of revolutions taken to cover the length by the circumference of the wheel.


    • This instrument does not provide accurate results on an undulating surface.


    • When the surface is smooth, the speedometer used in vehicles can be used.


    Chaining:-




    • In Chaining method, the distance is determined by means of a tape or a chain.


    • This is one of the accurate methods to determine the linear measurements.


    • The chain is used for ordinary precision.


    • Tape or a special bar is used to measure distance with high precision.


    • The distances determined by chaining form the basis of all surveying.



    • It is the accurate and commonly employed method in surveying.


    • No matter how accurately the angles may be measured, the survey can be no more precise than the chaining.



    • The instruments used for determination of the length of a line by chaining are chain or tape, arrows, pegs, ranging rods, offset rods and plumb bob.



    • Depending upon the material used, the tapes are classified as cloth or linen tape, metallic tape, steel tape and invar tape.



    Electronic method:-



    • Electronic equipment used for measuring distances is called an electronic distance measurement (EDM) instrument. 


    • They rely on the measurement of electromagnetic waves and measuring even fraction of wavelength by phase difference technique. 

    • Distances are measured with instruments that rely on propagation, reflection and subsequent reception of either radio or light waves.

    • The various instruments that are used under the electronic methods are Geodimeter, Tellurometer, the Decca navigator and the Lambda Position Fixing System.


    • The method of measurement in the case of Geodimeter is assessed on the propagation of modulated light waves. 

    • The other three instruments use radio waves for distance measurements.

    • These instruments even display the distance measured.

    • They are costly and delicate.

    • For ordinary surveying, they are not used commonly.



    Optical method:-



    • In this method, observations are taken through a telescope and distances are determined by calculation such as in tachometer or triangulation.

    • The tachometer (stadia is the common term in the USA) is a surveying method utilized to quickly determine the horizontal distance to, and elevation of, a point.

    • Stadia observations are accessed by sighting through a telescope equipped with two or more horizontal cross wires in a spacing that is known.

    • The apparent intercepted length between the bottom and top wires is read onto a graduated rod held vertically in the desired stage.

    • The space from the telescope to a rod is seen by proportional relationships in similar triangles.













    *Self Typed
    *Source- Internet, Books, Self-Analysis



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    About the Author

    Mr. Ashutosh Nautiyal is a student who is pursuing his post-graduation (MBA in Infrastructure Development and Management) from SCMHRD, Pune. He has done his B.Tech in Civil Engineering from BTKIT, Dwarahat and his schooling from Omkarananda Saraswat…

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