What is Plane Table Surveying?

• You need to perform small-scale surveying, like mapping out a field.
• You need to survey an industrial area where a compass survey doesn’t get any result.
• You need to fill in details between survey stations that are fixed by a triangulation or theodolite traversing method.

Types of Equipment Needed for Plane Table Surveying

• Drawing Board — Made of well-seasoned wood, the drawing board can come in a number of sizes. And it can be mounted on a tripod with a leveling head or a ball-and-socket mechanism. This is done in a way that allows it to be leveled and resolved across a vertical axis so it can be secured in any position.

• Alidade — A ruler that has a sight line attached and can be used on the plane table for bisecting a particular object. It can also be used to draw rays, direction lines, or anything similar. An alidade has a metallic or boxwood straightedge or ruler that’s approximately 45 centimeters long, and it has a beveled edge (called a “ruling edge, “working edge,” or “fiducial edge”).

• Spirit Level — This type of survey equipment can be very sensitive, and it’s used to level the table by placing it in two positions at right angles of each other and setting the drawing board so the bubble is evenly centered.

• Trough Compass — Consists of two bubble tubes that sit at right angles of each other and are mounted on a square brass plate. It can be used to determine the direction of the magnetic meridian on the paper.

• U-Frame or Plumbing Fork — Has a plumb bob attached to one end and can be used to center the table at a specific survey location. This type of survey equipment is often used for more large-scale projects, so the point on the paper can be placed directly over the station marked on the ground.

• Water-Proof Cover — Can be used to protect the paper sitting in the plane table from the rain.

• Paper or Drawing Sheet — The paper that’s used for plane table surveying should be high-quality because it’s very sensitive work that’s often prone to changes due to variation of humidity in the atmosphere. The paper can expand and contract in various directions and in varying degrees, which can alter or distort the map. So, it needs to be seasoned for about a week by exposing it to both damp and dry conditions. This will reduce the paper's tendency to distort.

• Tripod — This is one of the most important tools for plane table surveying because it would be impossible to perform this task without it. It can be used to secure the drawing board, and it has a screw at the bottom that can be used to set and level it according to the position of the theodolite or in any way that you see fit.