Methods of Plane Table Survey (Radiation, Intersection, Resection, Traversing)

Methods of Plane Table Survey (Radiation, Intersection, Resection, Traversing)

Plane table surveying is a graphical method in which observations and plotting are done simultaneously in the field. Various methods are used depending on the nature of the survey area and the type of work. The main methods of plane table survey are radiation, intersection, resection, and traversing. Each method has its own procedure and application.

1. Radiation Method

In the radiation method, the plane table is set up at a single station, and lines are drawn from this station to various points in the field. The distances are measured and plotted along these lines.

Procedure

• Set up the plane table at a station
• Mark the station point on the drawing sheet
• Use alidade to sight different objects
• Draw rays towards each object
• Measure distances and plot them to scale

Advantages

• Simple and quick method
• Suitable for small areas
• Easy to understand and perform

Disadvantages

• Not suitable for large areas
• Accuracy decreases with distance

2. Intersection Method

In this method, points are located by the intersection of rays drawn from two different stations. No direct measurement of distance is required.

Procedure

• Select two stations and measure the distance between them
• Plot the stations on the drawing sheet
• From both stations, draw rays towards the object
• The intersection of rays gives the position of the object

Advantages

• No need to measure distances to objects
• Useful for inaccessible points
• Provides good accuracy

Disadvantages

• Requires clear visibility from both stations
• More time-consuming than radiation method

3. Resection Method

Resection is used to determine the position of the plane table station by observing known points already plotted on the map.

Procedure

• Select known points visible from the station
• Sight these points using alidade
• Draw lines from known plotted points
• The intersection of these lines gives the position of the station

Methods of Resection

• Two-point problem
• Three-point problem

Advantages

• Useful when station position is unknown
• Helps in continuation of survey work

Disadvantages

• Requires known reference points
• Accuracy depends on correct orientation

4. Traversing Method

In traversing, the plane table is moved from one station to another, and survey lines are plotted successively.

Procedure

• Select a series of stations forming a traverse
• Set up the table at the first station
• Plot the next station using measured distance and direction
• Repeat the process for all stations

Advantages

• Suitable for large areas
• Can be used for route surveys

Disadvantages

• Errors may accumulate
• Requires careful orientation at each station

Comparison of Methods

Importance in Surveyor Trade

These methods are widely used in plane table surveying for mapping and fieldwork. Each method is selected based on the nature of the survey area and the required accuracy.

Conclusion

Plane table surveying methods such as radiation, intersection, resection, and traversing provide different ways to locate points and prepare maps. Understanding these methods helps surveyors choose the appropriate technique for different situations.

For ITI Surveyor trainees, mastering these methods is essential for developing practical surveying skills and ensuring accurate results.