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Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
The Three Steps of Plane Tabling
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Today we will learn about the three main steps involved in using a plane table effectively. Can anyone tell me what the first step is?
Is it levelling the table?
Correct! The first step is levelling the plane table. What do we use to level it?
A spirit bubble tube!
Exactly! Next, we need to centre the table. Can someone explain how we do that?
Using a plumb bob!
Well done! And lastly, how do we orient the plane table?
We can use a magnetic compass or the back ray method.
That's right! To recap: we level using a spirit level, centre with a plumb bob, and orient using a compass or back ray method.
Methods of Plane Tabling
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Now, let's dive into the four methods of plane tabling! Who can name one of these methods?
Radiation?
Yes! The radiation method involves using distance and direction. Can anyone explain how it works?
We set the table at a location and measure the distances to points around us, drawing rays to locate them on the map.
Excellent! What about the second method?
Intersection!
Right! This method helps to locate points using two directions from two stations. Let’s move to the third method.
Traversing!
Spot on! This is used when visibility is obstructed and involves multiple stations. Finally, what is the last method?
Resection?
Correct! Resection allows us to determine our unknown position by referencing known points. Great job, everyone!
Applications and Modern Relevance
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As we know, traditional plane tabling is becoming rare. Let’s discuss why that is. Can anyone give a modern alternative?
GPS and total stations!
Exactly! While these technologies provide more efficiency, what benefits do you think plane tabling has?
It’s very accurate and you can work in the field with minimal office work.
Right! The ability to check plotting errors on the spot is another advantage. However, what about its disadvantages?
It’s labor-intensive and not good in dense areas.
Perfect! Plane tabling, while less popular now, offers valuable techniques for understanding basic surveying principles.
Introduction & Overview
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Quick Overview
Standard
It details the processes of levelling, centring, and orienting the plane table, as well as describing the four methods of plane table surveying - Radiation, Intersection, Traversing, and Resection. Each method’s operational specifics and applications are examined, emphasizing their relevance in mapping despite modern technology overshadowing traditional approaches.
Detailed
Detailed Summary
The section elaborates on the process and methods involved in plane tabling, which has been a fundamental technique in surveying and mapping. Plane tabling involves three crucial steps: Levelling, Centring, and Orienting. Levelling is conducted using a spirit bubble tube to ensure the table is horizontal, while Centring requires a plumb bob for precise placement over a survey point. Orienting can be achieved using either a magnetic compass or the back ray method to align the table with true north.
Four main methods of plane table surveying are discussed:
- Radiation: This method involves taking distances and angles from a set point to locate various objects on a map.
- Intersection: Extensively used for plotting distant features, this technique uses two reference stations to triangulate the position of an object based on two line bearings.
- Traversing: This method is adopted in areas with limited visibility, using successive stations to plot details using either radiation or intersection methods.
- Resection: Useful for determining the location of an unknown point on a map by drawing lines from known points.
Despite the accuracy and immediacy of plane tabling in fieldwork, modern advancements like GPS and total stations have rendered traditional plane tabling methods almost obsolete. However, their foundational principles remain vital for understanding surveying techniques.
Audio Book
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Introduction to Plane Table Methods
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There are three steps to work with plane table; (i) Levelling the plane table, (ii) Centering the plane table, and (iii) Orienting the plane table.
Detailed Explanation
There are three critical steps involved in working with a plane table:
1. Levelling: This involves ensuring that the plane table is perfectly horizontal, which is typically done using a spirit bubble tube.
2. Centering: This step involves placing the plane table precisely over a point of interest on the ground. A plumb bob is used to ensure accuracy in centering.
3. Orienting: This step is crucial for accurately representing the plan. It can be done using a magnetic compass to align the table or by using a back ray method to reference back to a known point.
Examples & Analogies
Think of the plane table as a camera that needs to be level and precisely aimed at a specific target to take a good picture. Just as you level a camera and then focus on your subject, the surveyor levels the table and centers it above a point before orienting it to get the right view of the terrain.
Methods of Surveying with Plane Tables
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The equipment required for plane table surveying are shown in Figure 1.38:
There are four methods of plane table surveying: (i) Radiation, (ii) Intersection, (iii) Traversing and (iv) Resection.
Detailed Explanation
In plane table surveying, after setting up the table, there are four principal methods to gather data:
1. Radiation: This method uses distance and direction to locate objects. The surveyor measures distances to various points from the table's position and draws lines (rays) to mark these positions on the map.
2. Intersection: Used to locate points that are not directly visible. The surveyor measures angles from two known locations (stations) on a baseline and draws intersecting lines to pinpoint the position of an object.
3. Traversing: This method is employed when visibility is limited, allowing for the recording of points by moving the table to several stations.
4. Resection: This technique determines the position of the plane table when the location is unknown by back-sighting on two or three known points.
Examples & Analogies
Imagine you are navigating a new city without a GPS. Radiation is like getting directions from a landmark. Intersection is like figuring out your location by viewing two streets from a corner and finding where they meet. Traversing is akin to walking down a street and taking notes on the sights along the way, and resection is like trying to figure out where you are by referencing several visible buildings.
Obsolescence of Plane Tabling
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Now-a-days, plane tabling is considered as obsolete, and therefore is not carried out in the field. The field data is directly collected and stored using either Digital Levels, GPS or Total Station, and mapping is carried out using the capabilities of the software in a computer.
Detailed Explanation
In present times, the traditional method of plane tabling has largely been replaced by advanced technology. Methods like Digital Levels, GPS, and Total Stations offer much faster, more efficient, and precise data collection and mapping capabilities. These modern tools streamline the process by directly collecting and storing data, which can then be processed through specialized mapping software on computers, eliminating the labor-intensive steps of the plane table method.
Examples & Analogies
Consider the difference between using a traditional film camera to capture images and using a digital camera today. While both can produce photos, digital cameras are faster, easier to use, and allow for instant editing and sharing. Similarly, modern surveying techniques have surpassed plane tabling in efficiency and ease of use.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Levelling: Ensuring the plane table is horizontal.
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Centring: Accurately placing the table over the survey point.
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Orienting: Aligning the table with the terrain.
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Radiation Method: A way to map points based on direction and distance.
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Intersection Method: Locating points using two directions from two points.
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Traversing Method: Plotting points in obstructed visibility conditions.
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Resection Method: Finding the unknown location by referencing known points.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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Using the radiation method, a surveyor can plot features such as trees or buildings by measuring distances from the plane table.
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In an intersection method application, if two survey stations are established on a base line, angles can be measured to determine the location of a distant object.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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To level the table, bubble straight, centring's next, don’t be late! Orient well, with compass right, plane tabling's easy, what a sight!
📖 Fascinating Stories
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Imagine a surveyor in the field, carrying a wooden table and a spirit level. As they move to various sites, they take a plumb bob to ensure they center perfectly over each point, and they spin their compass to find true north before tweaking the angles for accurate mapping. This sequence of actions ensures the best possible outcome.
🧠 Other Memory Gems
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L-C-O: Level, Centre, Orient – the steps you need to survey well!
🎯 Super Acronyms
R.I.T.R. – Radiation, Intersection, Traversing, Resection – remember these methods to master plane tabling!
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Levelling
Definition:
The process of making the plane table horizontal using a spirit bubble tube.
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Term: Centring
Definition:
Positioning the plane table directly over a survey point using a plumb bob.
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Term: Orienting
Definition:
Aligning the plane table with a reference direction using a magnetic compass or back ray method.
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Term: Radiation
Definition:
A method of locating points on a map by measuring distances and directions to those points.
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Term: Intersection
Definition:
A technique for locating an object by taking directions from two different stations.
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Term: Traversing
Definition:
Plotting details by occupying multiple stations, especially in obstructed visibility areas.
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Term: Resection
Definition:
Determining the position of an unknown point by drawing rays from known points on the plane table.