Jawaharlal Nehru Technological University Hyderabad B.Tech II SURVEYING Previous Question Paper (September - 2021 - R13)

Plane table surveying is a graphical method where the field work and plotting are done simultaneously. Its merits include: the plan can be drawn in the field, allowing the surveyor to compare it with actual ground features; it is ideal for magnetic areas where compass surveying fails; errors are easily detected as the work is plotted on-site; and it is generally faster and more economical for small-scale mapping. Its demerits include: it is unsuitable for work in wet, rainy, or windy weather; it requires a large amount of equipment to be transported; it lacks high precision compared to theodolite surveying; and it is not suitable for accurate work in dense forests or areas with poor visibility.

Resection is a method of plane table surveying used to determine the station point occupied by the plane table by observing well-defined points whose positions have already been plotted on the drawing sheet. The process involves orienting the table at the unknown station and drawing rays from the known points to intersect at the station point.

It differs from other methods like radiation, intersection, and traversing in the following ways:

• Purpose: While other methods are used to locate details or plot new stations from a known station, resection is specifically used to locate the instrument station itself.
• Dependency: Radiation and intersection require the instrument to be at a known station to locate unknown points. Resection requires the instrument to be at an unknown station to locate that station relative to known points.
• Orientation: Resection inherently requires the table to be oriented (e.g., by back-raying or the three-point problem) before the station can be fixed, whereas in radiation, the orientation is fixed by the initial setup at a known point.