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Tuesday, September 29, 2020

Advantage and disadvantage of plane table survey

 Advantage

•       It is most suitable for preparing for small scale maps.

•       It is the most rapid method

•       Field book is not necessary as plotting is done in the field concurrently with the fieldwork and hence the mistakes in booking the field notes are avoided.

•       The surveyor can compare the plotted work with the actual features of the area surveyed and thus can ascertain if it represents them properly and cannot overlook any essential features.

•       There is no possibility of omitting the necessary measurements as the map are plotted in the field.

•       Errors of measurements and the plotting may be readily detected by check lines.

•        Counters and irregular objects maybe represented accurately since the tract is in view.

•       It is particularly advantageous in a magnetic area where compass survey is not reliable.

•       It is less costly than a theodolite survey.

•       No great skill is required to prepared maps.

Disadvantage

•       Plane table is essentially a tropical instrument.

•       It is not suitable for work in a wet climate.

•       It is heavy and awkward to carry.

•       There are several accessories to be carried they are like to be lost.

•       It is not intended for accurate work.

•       If the survey is not to be re-plotted to a different scale or quantities are not to be computed.

•       It is a great inconvenience in absence of the field notes.

(Case : 1 When the line of sight is horizontal and staff is held Vertical) Example 3

Example 3 A staff held vertically at a distance of 50 m and 100m from the centre of the theodolite with a stadia hair, the staff intercept w...