Correct Answer - Option 3 : It is essentially a tropical instrument
Concept:
Plane-table survey:
A plane table surveying is a graphical method of surveying. In this method of surveying, field observation and plotting are done simultaneously helping the surveyor to compare the plotted details with actual features of the ground.
Advantages of Plane Table Survey:
- It is suitable for the location of details as well as contouring for small-scale maps directly in the field.
- As surveying and plotting are done simultaneously in the field, chances of getting omission of any detail get less.
- The plotting details can immediately get compared with the actual objects present in the field. Thus errors, as well as the accuracy of the plot, can be ascertained as the work progresses in the field.
- It is less costly than a theodolite surveying
- It is advantageous in magnetic areas
Disadvantages of Plane Table Survey:
- The Plane Table is essentially a tropical instruments. It is not suitable to work in wet climate.
- This method of survey is not very accurate and thus unsuitable for large-scale or precise work.
- As no field book is maintained, plotting at different scale require full exercise.
- The quality of the final map depends largely on the drafting capability of the surveyor.
The setting of Instruments:
- Fixing
- Leveling
- Centering
Different methods for plane table survey:
- Radiation
- Intersection
- Traversing
- Resection