Plane Table Surveying: Understanding the Terminology
Plane Table Surveying is a surveying technique that requires knowledge of the different terms used. It is important to understand the meanings of each term used in plane table surveying in order to effectively perform the surveying procedure.
Meanings of Plane Table Survey Terms
Each term used in plane table surveying has a specific meaning and serves a certain purpose. It is important to familiarize oneself with these terms in order to accurately determine their meaning during the surveying process.
Terms Used in Plane Table Surveying
1. Centering
What is Centering?
Centering is a process used in plane table surveying that ensures the plotted position ‘o’ on the drawing sheet is accurately overlaid with the ground station ‘O’. This process is used to ensure that the data collected from the ground station is accurately represented on the drawing.
2. Orientation
What is Plane Table Alignment?
Plane Table Alignment is a process of aligning a plane table in the horizontal plane so that all the plotted lines are parallel to the corresponding ground lines. This is done by using a trough compass and back sighting or resection.
How to Perform Plane Table Alignment?
Plane Table Alignment is done by rotating the plane table in the horizontal plane. A trough compass is used to determine the direction and angle of the ground lines. Back sighting or resection methods are then applied to accurately align the plane table.
3. Back Sight
What is Back Sight?
Back Sight is a method of orienting a Plane Table from one known station to another. This is done by aligning the alidade of the plane table along a plotted line between the two stations, and then rotating the plane table until the second station is bisected. This process is used to orient the plane table in the direction of the second station.
How to Back Sight a Station?
To back sight a station, the Plane Table should be centered over the first station, A. Then, the alidade should be aligned along the plotted line between the two stations, A and B. The Plane Table should then be rotated until the station B is bisected. This process will orient the Plane Table in the direction of the second station.
4. Fore Sight
What is Fore Sight?
Fore Sight is a surveying technique used to determine a position of an un-marked station on a drawing sheet. It is typically used in plane table surveying, where a surveyor looks in the direction of the unknown station through a telescope and measures the angle and distance to that station. This information can then be used to calculate the station’s position.
5. Radiation
What is Radial Line Method?
Radial line method is a technique used for locating a point by drawing a radial line from the plane table station to the station under consideration.
Setting up the Plane Table
Before using the radial line method, it is important to set up the plane table and ensure proper orientation.
Drawing a Ray
Using the alidade, a ray is drawn in the direction of the point.
Measuring the Distance
The distance of the point is then measured and cut off to a suitable scale.
6. Intersection
What is Intersection in Plane Table Surveying?
Intersection in plane table surveying is a method of locating a point by intersecting two rays drawn from two different stations. This method is commonly used when it is not possible to measure the radial distance of the unknown point due to an obstruction, making it impossible to use the radiation method.
7. Resection
What is Resection in Plane Table Survey?
Resection in plane table survey is a method of locating a station occupied by the plane table when the position of that station has not been previously plotted on the drawing sheet. This is done when the plane table is occupying a station other than the station already plotted.
Two-Point Problem
Resection can be done by sighting two points whose positions have already been plotted in the two-point problem. This involves taking a line of sight from the plane table station to two points whose positions have already been plotted on the drawing sheet. The intersection of these two lines of sight will indicate the location of the plane table station.
Three-Point Problem
Alternatively, resection can also be done by sighting three points whose positions have earlier been plotted in the three-point problem. This involves taking a line of sight from the plane table station to three points whose positions have already been plotted on the drawing sheet. The intersection of these three lines of sight will indicate the location of the plane table station.
8. Plane table traversing
Plane Table Traversing
Plane Table Traversing is a method of surveying that is used to navigate around a plane. This method involves plotting traverse lines on a drawing sheet with the help of an alidade, without taking any angle measurements. This technique can be used to survey large areas efficiently and accurately.
What are the Terms Used in Leveling and their Uses in Surveying?
Leveling is a surveying technique used to determine the height of a particular location relative to a predetermined reference point. Leveling involves the use of certain terms such as benchmarks, offsets, backsights, foresights, and theodolites. Benchmarks are points of known elevation used as reference points, offsets are the difference in height between two points, backsights are the measurements taken from the point of known elevation, foresights are the measurements taken from the unknown elevation point, and theodolites are used to measure angles.
Equipments for Plane Table Survey and Their Uses
Plane table surveying requires the use of certain equipment in order to be successful. These pieces of equipment include an alidade, which is used to draw the traverse lines on the drawing sheet, a plane table, which is used to set up and draw the traverse lines, a plane table tripod, which is used to hold the plane table steady, a measuring tape, and a surveying rod. These equipments are essential for successful plane table surveying.