#Surveying #CES #oneliner

🎖 Plane table surveying

🔸 Principle of plane table is parallelism

🔸 The North line of the map is marked on the right hand top corner

🔸 It is graphical method of surveying where the field work and plotting are done simultaneously.

🔸 The working edge of the alidade is called fudicial edge or bevelled edge

🔸 Orientation :- The preparation of keeping the plane table at each station parallel to the position occupied at the previous station is known as orientation.

🔸 Orientation by back sighting is more accurate than magnetic needle method

🔸 Methods of plane table

👉 Radiation :-

~ Detailed plotting generally done by radiation.

~ These method is suitable for survey of small areas which can be done for a single station.

👉 Intersection :-

~ It is employed when inaccessible points to be surveyed

~ Suitable for hilly areas

👉 Traversing :-

~ It is used to plot the areas

👉 Resection :-

~ Resection is the process of finding the location of plane table with the help of known locations.

~ Resection is done by following methods

1. Compass method

2. Back ray method

3. Two point method :-

~ It is more laborious than three point problems

~ Orientation of plane table by solving two point problems is adopted only when given points are accessible

4. Three point problems

~ methods of Three point problems

A. Trial & error (Lehmann's method) :- It is more accurate and quick

B. Mechanical method (tracing papar)

C. Graphical method (Bessel's method)

🔸 Sizes of Plane table
👉 Large :- 750 × 600 mm
👉 Medium :- 600 × 500 mm
👉 Small :- 500 × 400 mm
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