Plane Table Surveying is a type of engineering survey. In this type of surveying the filed data should be plotted simultaneously in the table. No need to work in an office because all the designs should be planned during the survey in the field. This is a very simple and easy way to collect data from the field. So we will discuss plane table surveying and methods in detail:
What is plane Table Surveying?
Plane Table Surveying is a very easy and quick method of surveying. In this type of method of surveying the plotting and observation of the field, the object is taken simultaneously ( same time/same field). Both work design and observation are taken in the field. No need to work in the office for this surveying. So this type of surveying is faster than others.
A survey tool is to finish a survey by making a small map or diagram. During this survey, its survey equipment can cover small areas for its size. This survey is extremely difficult for large-scale plotted maps. Time consumption during this survey is minimal. Field observations and plotting were completed at the same time.
A plane table is a plane table surveying instrument that is used for measuring and sighting. This tool is used in traditional surveying like plane table surveying. The plane table helps to take all the earth’s measurements and maps of the earth.
Definition of plane Table Surveying
Plane Table surveying is type of Land surveying menthod in which field work and design work is simultaneously. Where a flat table is set up at the survey site. The surveyor uses the table as a base for drawing a map directly in the field, integrating measurements and observations. This technique provides real-time mapping and is particularly useful for small-scale topographic surveys.
Principal of Plane Table Surveying
The main Principle of Plane Table Surveying is dependent on parallelism.
According to the parallelism, All the rays drawn through the various details should pass through the survey station.
The position of the plane table is kept identical in each of the stations. This is done by orienting the plane table in the direction of magnetic north in each station on the ground.
The Main Objective of Plane Table Surveying
I have mentioned the Main Objective of Plane Table Surveying
- To prepare the small-scale maps.
- To mention the small area of topographic details on the field.
- To carry out small-scale ground details.
- This survey is done where the compass survey is not possible.
- To minimize the time-consuming.
- To increase the precision of the surveying in the field.
What are the instruments used for the Plane Table Surveying?
Plane table
The plane table is that the small drafting board is mounted on a light tripod in such how that they rotate about a vertical axis and clamped be any position. The paper was restored to the plan table. The table is made of well-seasoned timber in various sizes. 75 cm X 60 cm square, 50 cm X 60 cm square, and 40 cm X 30 cm sizes are mostly used in the survey.
Sizes are
Small Size: 40 cm X 30 cm square
Medium Size: 50 cm X 60 cm square
Large Size: 75 cm X 60 cm square
Alidade
A plan alidade is an essential tool in plane table surveying. It consists of a straightedge with a sight vane and sights at each end. Surveyors use it to sight distant objects and align the plane table with plotted points, facilitating accurate mapping and measurement in the field.
It is a wooden or brass ruler about 50-60cm long. it’s also called a sight ruler. it’s are two types:
Plain alidade: it’s a metal or wooden ruler about 50 cm. Sight vans are provided with a fiducial edge. It is an important instrument for the plane table survey.
Telescope alidade: It contains a telescope for sighting. It does not provide a sight van.
It is the metal strip bent within the slope of u ‘U’ that has an equal arm of length. the highest arm is a point and the bottom arm carries a hook for suspended plumb. This is used for centering the table over the station.
Spirit level
It is a tiny metal tube containing a small bubble of spirit. The bubble is visible for the highest graduated glass tube. Specially used for leveling a surveying instrument.
Compass
A compass is an instrument, used for determining the north-line direction. A special magnet is used within the compass. So, it’s called a compass. Without a compass, a plantable can be impossible. Generally, a Trough compass is mostly used in this surveying.
Plumbing Fork with plumbob
I hope you are used to plumbing forks during plane table surveying. This is a U-shaped instrument that is fitted at the pin of one side and the other side is fitted with a plum bob.
The main purpose of this instrument is centering the plane table and transferring the ground point in the paper.
Temporary adjustment of Plane Table Survey
The main function of a plantable survey is a temporary adjustment. The starting phase of the surveying instrument survey is an adjustment. Data is often observed with accurate adjustment. The following three methods are for Temporary adjustment for every station in surveying instrument survey:
Centering
After fixing the paper on the surveying instrument an appropriate point is chosen on the sheet to represent the bottom point with the assistance of a plumbing fork. The vertically dropped plumbing fork is accurate in measuring the middle of a ground point.
Leveling
leveling the extended by placing the level spirit level at the various corners and various positions on the table. The bubble is delivered to the middle of its run at every position of the table by adjusting the leg. The spirit bubble should be horizontally fixed on the table.
Orientation
when the surveying instrument survey is conducted by connecting the stations, the orientation must be performed at every successive station, orientation is often done by using through compass and back sighting. For the gathering ground point, orientation is the important part. the rear sight orientates and foresight orientates are the most.
Methods of Surveying of Plane Table Survey
The following are the methods of plane table surveying:
- Radiation
- Intersection
- Traversing
- Resection
Radiation Method
This method is suitable for locating the thing from the only station. during this method rays were drawn from the station to the objects and distance was measured and plotted suitable scale.
Intersection Method
This method is suitable for locating inaccessible points by the intersection of rays from the instrument station. The intersection method employs when the inaccessible point is visible from the instrument station but the linear distance is way from the station.
Traversing Method
This method is suitable for connecting the traverse station to every other. This method is analogous to compass and Theodolite traverse. Field observation and plotting are completed simultaneously with the assistance of the radiation and intersection method.
Advantages of Plane Table Surveying
The following are the Advantages of a Plane Table Survey:
Plane Table surveying is a very quick and easy type of surveying.
Office work is eliminated in plane table surveying.
Plane table surveying does not require skill and experience to prepare a map.
For small area can be included in this survey.
If the area is magnetic but the compass surveying is not possible then this survey is done.
The survey provides accurate contour and irregular objects on the ground.
The cost of this surveying is much cheaper than other types of surveying.
In-plane table The errors of the field book are eliminated.
The map is prepared on the field.
Disadvantages of plane Table Surveying
Plane Table is not suitable for a large area.
This type of survey is extremely affected by climate conditions. It is not possible to carry out in monsoon or highly winded seasons.
In this survey, the instrument is set up at each station on the ground.
A plane Table survey is not suitable in foggy areas due to the lack of visibility of the ground objects.
Using instruments is very heavy so the instrument is not handled properly, it is so hard to handle due to heavy.
This survey makes it very hard to re-prepare the map on a different scale.
This is the Plane Table Survey information. All about this information is very helpful to you. I hope this article is very helpful to you. if you like please share with other friends. Thanks for viewing my site. If you’ve got any doubt please contact me.