Surveying (General Engineering) (SSC JE)

There are following are the fundamental lines of a theodolite–
1. The vertical and horizontal axis
2. The line of collimation and axis of the plate level
3. The bubble line of the altitude level
4. Axis of plate bubble tube
5. Axis of telescope

Arrows are used for counting the number of chains while measuring a chain line. An arrow is inserted into the ground after every chain length measured on the ground.

After completion of a chain the leader inserts an arrow and follower picked that one on next chaining operation. As follower has 6 arrow so the distance of the follower from the starting point is 6 chain.

HI method– Height of the instrument method of leveling is less accurate than rise and fall method. In this method, the height of instrument is calculated for each setting of the instrument by adding for each setting of the instrument by adding back sight to the elevation of the BM.

The elevation of reduced level of the turning point is then calculated by subtracting from HI the foresight.

Intersection methods of plane table surveying is used to locate the position of an inaccessible points. It is most suitable for hilly area and also known as graphical triangulation.

In order to determine the natural features such as valleys, rivers, lakes, etc. this surveying preferred is topographical surveying.

Cadastral surveying–Cadastral surveying are made incident to the fixing of property lines, the calculation of land area or the transfer of land property from one owner to another.

The constant vertical distance between two adjacent contours is called contour interval (CI).
It depends on following factors–
1. Scale of map ∝ 1/CI
2. Nature of country
3. Purpose of map more detail small CI
4. Time and funds ∝ 1/CI

Sensitivity–It is the ratio of the change in the output of an instrument to a change in the quantity being measured.
• The reciprocal of sensitivity is called deflection factor or inverse sensitivity.