What is the function U fork with plumb bob?
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.
What is the use of plumbing fork?
5. U fork or plumbing fork with plumb bob- The U fork is a metal strip bend in the shape of U having equal arm length. The top arm is pointed and bottom arm carries a hook for suspending a plumb bob.
What is the function alidade?
An alidade (/ˈæ. lɪ. deɪd/) (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. At one time, some alidades, particularly using circular graduations as on astrolabes, were also called diopters.
What are the accessories required in plane tabling?
Alidade. Plumbing fork with plumb bob. Spirit level. Trough compass.
Which is the most accurate method of orientation?
Orientation by Backsight- This method is always accurate and it is always preferred. Suppose A and B are the two station. The plane table is set up over A. the table is levelled by spirit level and centre by U fork so that point a is just over a station A.
What are the types of alidade?
Alidade
- The alidade is useful for establishing a line of sight.
- Two Types of alidade are used.
- Simple alidade.
- Telescopic alidade.
How many ways are there to orient a plane table?
How many methods of plane table surveying are there? Explanation: There are four ways to perform plane table surveying. They are radiation, inter-section, traversing and resection. First two are employed for locating details and other two for locating plane table stations.
Why horse hair is used in alidade?
horse hair. Both the slits, thus provide a definite line of sight which can be made to pass through the object. edge is known as the fiducially edge. The fiducially edge is graduated to facilitate the plotting of distances to a scale.
Who invented alidade?
NMAH | Surveying & Geodesy | Transit. The transit was the most important surveying instrument in the United States in the 19th century. But William J. Young, who invented the form in 1831, did not see it as something new, but simply a modification of his new railroad compass.
What are the different types of alidade?
Two types of alidade are used in plane table surveying, they are plain alidade and telescopic alidade.
What is Bowditch rule?
1)Bowditch’s Rule: The Bowditch’s rule, also termed as the compass rule, is mostly used to balance traverse when linear and angular measurements are equally precise. By this rule, the total error in latitude or departure is distributed in proportion to the lengths of the traverse legs.
How does a plumbing Fork work on a plane table?
Plumbing fork is a U-shaped metal frame with a upper horizontal arm and a lower inclined arm. The upper arm is provided with a pointer at the end while the lower arm is provided with a hook to suspend plumb bob. When the plumbing fork is kept on the plane table the vertical line (line of plumb bob) passes through the pointed edge of upper arm.
How are the lines drawn on a plumbing Fork?
Lines are drawn along the straight ruler. It is also mounted with a vertical circle that gives us the angle of the object with the horizontal axis. Plumbing fork is a U-shaped metal frame that has two different types of arms.
What is the meaning of the plumb bob?
A plumb bob, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum .
Why are plumb bobs used on tall buildings?
Until the modern age, plumb bobs were used on most tall structures to provide vertical datum lines for the building measurements. A section of the scaffolding would hold a plumb line, which was centered over a datum mark on the floor.
