đź•‘ Reading time: 1 minute

Contents:

  • What is Aeroplane Table Surveying?
  • Equipment Used in Plane Tabular array Survey
  • Airplane tabular array survey equipment is arranged in four steps as follows
    • Fixing of Plane Table
    • Leveling of Plane Table
    • Centering of Airplane Table
    • Orientation of Aeroplane Table
  • Methods of Aeroplane Tabular array Surveying
    • Radiation
    • Intersection
    • Traversing
    • Resection
  • The Three-Signal Problem
    • Tracing Method in Aeroplane Table Surveying
    • Lehmann Method
    • Analytical Methods
    • Graphical Method
  • The Two-Bespeak Trouble

What is Plane Table Surveying?

The plane table surveying is the fast method of surveying. In this type of surveying plotting of the program and field observations can be washed simultaneously. In case of plane table surveying Geometrical conditions of site are manuscript in the map sheet using airplane table and alidade afterward that topographic details are arranged on the map.

Equipment Used in Plane Table Survey

Full general equipment used for conducting aeroplane table survey are

  • Plane tabular array
  • Alidade for sighting (telescopic or simple)
  • Plumb bob and plumb fork
  • Compass
  • Spirit level
  • Chain
  • Ranging rods
  • Tripod
  • Drawing sheet and drawing tools
  • Paper clips or screws

Plane Table Surveying

Plane tabular array survey equipment is arranged in 4 steps every bit follows

Fixing of Aeroplane Table

Fix the airplane table to the tripod stand. Conform the drawing sheet on the plane table using paper clips or pollex screws. The sheet should be in one position from kickoff to last.

Leveling of Plane Table

Plane tabular array should be leveled using spirit level. For small works, eye estimation can be ok.

Centering of Plane Table

The tabular array should be centered past using plumbing fork. By which we tin can arrange the plotted bespeak exactly over the basis indicate.

Orientation of Plane Table

Whenever we are using more one instrument station, orientation is essential. It can be done by using compass or back sighting. In this case, the plane table is rotated such that plotted lines in the cartoon sheet are parallel to corresponding lines on the ground.

Methods of Plane Table Surveying

Generally in that location are 4 methods are available to perform plane table surveying. They are

  1. Radiation
  2. Intersection
  3. Traversing
  4. Resection

Radiation

In this method, plane tabular array is located at one bespeak "o" as shown in fig. and perform the whole from that point. From point O, sight the points A,B,C,D and E using alidade, locate and plot the points as a,b,c,d and e in the cartoon canvas. Plane Table Survey - Radiation

Intersection

In this method we can locate the indicate past plotting two rays from two known stations. As shown in effigy, P and Q are the known station. Kickoff the equipment is placed on P and plot the lines by sighting the stations A, B and Q. then shift the equipment to station Q and plot the lines past sighting stations A, B and P. Finally, the intersection of A and B rays is the required location of point of intersection. Plane Table Survey - Intersection

Traversing

Traversing is the connexion of series of straight lines. In the case of traversing, the plane table is located at i indicate for supposing A equally shown below. From that point sight towards B and measure the distance AB. Then shift the airplane table to betoken B and sight towards A and measure BA. The average distance of AB and Ba are plotted to scale in the cartoon sheet. Then Sight the betoken C from B and measure BC and echo the aforementioned procedure until the concluding betoken. Conduct some checks at some points. Finally, traverse lines are plotted on the drawing sheet. Plane Table Survey - Traversing

Resection

Resection is a method of plane tabular array surveying in which the location of the plane table is unknown and it is determined by sighting it to known points or plotted points. It is besides chosen the method of orientation and information technology can be conducted past 2 field conditions as follows.

  • The three-point problem
  • The ii-signal problem

The 3-Point Trouble

In this condition, three points and their positions in the field are known. The plane table is placed at an apposition from where all the three points are visible. Then, by sighting those three points we can locate the point where equipment is located. This can be achieved by many methods every bit follows.

  • Tracing method
  • Lehmann method
  • Belittling methods
  • Graphical method

Tracing Method in Plane Tabular array Surveying

In the tracing method, the plane table is located at a betoken from where 3 points are visible. The tabular array is oriented with respect to the plotted lines of those three points. Place the tracing newspaper on the drawing sheet and again sight the 3 points and plot the radiating lines. The tracing paper is then moved in a higher place the drawing sheet until the three radiating lines pass through corresponding points previously plotted on the map. Finally, the position of the plane table is marked. Tracing Method in Plane Table Surveying

Lehmann Method

In this method, Plane tabular array is located at a bespeak P and sight the station A, B and C and plot the rays Aa, Bb, and Cc. The rays form pocket-size triangle which is called triangle of error. Another point P1 is chosen to reduce the error and sight the point A from P1 similarly to B and C. which will give some other triangle of error. Echo this procedure until fault becomes cypher. Lehmann Method of Plane Table Surveying

Analytical Methods

There are many analytical methods are adult in 3-signal problem condition. In this method, from station P A, B and C are sighted and annotation the values of angles and lengths. From these values make up one's mind the position of unknown points by using analytical formulae.

Graphical Method

In graphical method besides, angles and lengths are adamant and represented it on a graph and determines the location of aeroplane tabular array.

The Two-Bespeak Problem

In the two-point trouble, ii points are sighted from other point corresponding to the points given in aeroplane table sheet. Here two cases are to be discussed. Case 1: when the points tin be occupied by the plane tabular array As shown in fig. A and B are the 2 points corresponding to the points a and b. Now, airplane table is located at B and oriented past sighting A. sight C from B and bx is plotted on the sheet. Then shift the plane table to C, oriented by backsighting B along xb. And then alidade is placed over a and sight station A, then line Aa cuts the line bx at somewhere which is located equally indicate c at station C. The Two-Point Problem Case2: When the plane table cannot occupy the controlling stations In this case, an auxiliary indicate D is considered nearer to C. Locate the plane table at D co-ordinate to the line ab parallel to AB. So sight the station A and B corresponding to a and b. the rays fatigued are intersected at some point which is marked as d. then sight towards C by placing alidade at d. mark the distance Dc as c1. Shift the table to C and backsight to D with reference to c1. Then sight A corresponding to a, the ray drawn is intersects the previously fatigued ray from D in c2. From c2 sight B describe a ray which intersects db and marked the intersection as b1. The table is oriented till ab comes in line with P. From P sight and draw rays Aa and Ba. The intersection of these ii rays will give the Location of Point C. The Two-Point Problem Read More: Equipments for Plane Table Survey and Their Uses Theodolite Parts and its Functions for Angle Measurements in Surveying Equipment Used for Measuring Angles and Elevations in Surveying