Surveying

•    Surveying is the technique of measuring the area, which enables us to determine the relative positions of various points on the earth’s surface. Surveying helps in preparing different types of maps, topographical maps, layout plans of roads, railways, building and multipurpose projects. There are different types of survey that are classified on the basis of accuracy, purpose, and instruments.
•    Plane table survey is conducted with the instrument known as plane table. In this survey, field work and plotting are done simultaneously in the field. This helps the surveyor to compare the plotted details with actual features of the ground.
•    Instruments used in a plane table survey are:
a.    Plane table with a tripod stand
b.    Alidade
c.    Spirit level
d.    Plumbing fork and plumb bob
e.    Trough compass
f.    Chain
g.    Measuring tape
h.    Arrows
i.    Ranging rods
j.    Drawing material, i.e., paper, allpin, drawing pin, rubber, pencil, etc.
•    Following steps are taken to conduct a plane table survey:
a.    Preparing the rough sketch
b.    Setting the plane table, which includes levelling, centering and orientation
c.    Fixing the base line
d.    Drawing of rays
e.    Re-orientation by back sighting or trough compass
•    There are three different methods of plane table surveying to carry out operations in different field conditions. These are:
a.    Radiation method
b.    Intersection method, and
c.    Traverse method
•    In Radiation Method, only one station is used in surveying the entire area. This method is used when a small area is to be surveyed, which are within a single tape length from the location of plane table.
•    Intersection method of plane table surveying is used for conducting surveys of large areas or the areas that cannot be measured properly. In this method, the plotting of plane table stations is to be carried out accurately.
•    Traverse Method is used to survey large areas such as road, railway line, canal, settlements, etc. The stations are plotted by method of radiation by taking back sight on the preceding station and a fore sight to the following station.

 

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  • Q1

    Explain the first step of plane table surveying.

    Marks:2
    Answer:

    The first step for conducting the plane table survey is preparing the rough sketch. The rough sketch of the area to be surveyed is to be prepared. Important points should be noted and illustrated with the use of conventional signs. Ranging rods are fixed on important points.

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  • Q2

    List all the instruments used in conducting plane table surveying.

    Marks:2
    Answer:

    Instruments used in conducting plane table surveying are:
    i. Plane table with a tripod stand

    ii. Alidade
    iii. Spirit level
    iv. Plumbing fork and plumb bob
    v. Trough compass
    vi. Chain
    vii. Measuring tape
    viii. Arrows
    ix. Ranging rods
    x. Drawing material

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  • Q3

    Name the different types of chains used in surveying.

    Marks:1
    Answer:

    Three types of chains are used in surveying.
    i. Engineer’s Chain

    ii. Gunter’s Chain
    iii. Metric Chain

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  • Q4

    Name the surveys which are based on instruments used.

    Marks:1
    Answer:

    Three types of surveys based on instrument used are:
    i. Chain and Tape Surveying

    ii. Plane table surveying
    iii. Prismatic compass surveying

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  • Q5

    What is a plane table survey?

    Marks:1
    Answer:

    Plane table survey is based on instrument known as plane table. In this survey field work and plotting are done simultaneously in the field.

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