Plane Table Surveying - Advantages, Disadvantages, Methods.

•  Introduction :

Plane table surveying is one of the important methods used for surveying in which fieldwork and surveying is done simultaneously on the filed so that plane table has not office work required and where high precision is not required plane table surveying is used such as small mapping area or medium filed.

 

Plane Table Surveying

• Plane table surveying instrument :

For plane table surveying some instrument is needed for completing survey some important instrument is given below:

1. Drawing Board :
2. Alidade Spirit :
3. level rough :
4. Compass :
5. U-Frame or Plumbing Fork:
6. Water Proof Cover:
7. Paper or Drawing Sheet:
8. Tripod:
   

• Principle of Plane Table Surveying  :

1. To distinguish clearly, little letters like p, q, r, etc. ought to be used on the paper to represent the corresponding points P, Q, R, etc. on the bottom.
2. whereas taking the sights, the table ought to be clamped in position, and therefore the alidade should be focused on the aforethought station purpose on the paper or drawing sheet.
3. The table should solely be turned for orientation, and once it's properly oriented, it ought to be once more clamped in position.

• The setting of equipment for Plane Table Surveying :

1. Fixing of Plane Table :
2. Leveling of Plane  Table :
3. Centering Plane Table :
4. Orientation Plane Table :

1.  Fixing of Plane Table :

Fix the plane table on tripod stand. arrange the drawing sheet on plane table using a paper clip or thumbscrews. the sheet should be fixed during a drawing of survey details.

2.  Leveling of Plane  Table :

Plane table should be leveled using spirit level. for small works with eye, estimation is done.

3. Centering Plane Table :

The table should be centered by using plumbing fork. By which we can arrange the plotted point exactly over the ground point.

4. Orientation Plane Table :

Plane table use more than one instrument station so that orientation is essential. in plane table is rotated that plotted lines in the drawing sheet are parallel to the survey line on ground drawn.

 There are 2 methods:

1. Magnetic Needle:
2. Back Sighting:

   Ø        Advantages and Disadvantages of Plane Table Surveying :

• Advantages of Plane Table Surveying :

1. Map of the area is plotted on sheet on filed i.e filed work and mapping is done simultaneously.
2. Any type of measurement book is required, and thus office work is eliminated.
3. only finishing drawing, office work is required.
4. Plane table surveying is not affected by magnetic declination, so plane table easy to use in the magnetic area.
5. It is most suitable of small and medium mapping areas.
6. It does not required labor for surveying so that time-consuming.
7. Time-consuming survey.
8. Contour survey has done accurately.

• Disadvantages of Plane Table Surveying :

1. Plane table survey is not suitable in wet climates, in places where high winds predominant and in wooded country.
2. For large area survey plane table survey is not used.
3. Plane table survey is not an accurate survey method so it is not used for a detailed survey.
4. Plane table is not able to get details measurement.

• Methods of Plane Surveying :

1. Radiation method of plane tabling:
2. Intersection or triangulation method of plane table surveying:
3. Reversing method of plane table survey:
4. Resection method of plane table survey:

 ·        Errors in Plane Tabling Surveying : 

   In surveying various surveys carried out so in every survey has different errors just like that in plane table surveying some errors occur during surveying.

1. Instrumental errors. 
2. Errors of manipulation and sighting.  
3. Errors of Plotting.