Surveying (General Engineering) (SSC JE)

Given,
Distance of lamp from the station = 30 km
Height of light house = H
• Distance of an object at visible horizone–
D = 3.855 √H
30 = 3.855√H
H = 60.57

The plane table is an instrument used for surveying by a graphical method in which the field work and plotting are done simultaneously.

The main advantage of plane tabling is that the topographic features to be mapped are in full view. It is most suitable for small and medium scale mapping (1 : 10,000 to 1 : 2,50,000).

Theodolite–It is an instrument used to measure horizontal and vertical angles. It was invented by Remer a Danish astronomer in 1690

Radiation–In this method the instrument is setup at a station and rays are draw to various station which are to be plotted. This method is suitable only when the area to be surveyed is small and all the required stations to be plotted are clearly visible and accessible from the instrument station.

Traversing–This method is similar to compass or theodolite traversing. The table is set at each of the stations in succession. This method is most suitable when a narrow strip of terrain is to be surveyed. E.g. Survey of roads, railways etc.

Intersection–This method is most commonly ued for plotting details. It is preferred when the distance between the stations is too large, the stations are inaccessible or the ground is undulating.

Resection–This method of orientation is employed when the plane table occupies a position not yet plotted on the drawing sheet.

Offset–It is the distance of the object from the survey line. It may be perpendicular or oblique. The purpose of offset is to locate the objects which lie in the vicinity of the main survey line.

Given that,
For bearing (FB) = S49⁰ 52′E If the fore bearing of a line is given as the quadrantal bearing (QB) then back bearing is numerically equal to the fore bearing. However N changes to S and E changes to W and vice versa.
∴ Back bearing of line (BB) = N49⁰ 52′W

Relation between radius of curve (R) and degree of curvature–
Case 1: Let arc length is 30 mm and radius of curve in R the n degree of curve is D.Case 2: Let arc length is 20m and radius of curve is R the n degree of curve is D.

Ideal transition curve– A clothoid or spiral is an ideal transition curve in which the radius of curvature at any point is inversely proportional to the distance of the point from the beginning of the curve.

Length of transition curve– The length of a transition curve should be such that full superelevation is attained at the end of the transition curve and applied at a suitable rate.