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Compass Surveying: Types and Differences

Compass Surveying: Types and Differences

Surveying is an important step for any type of project. A compass is an instrument that is small in size. It is used to measure the angle of two points. The magnetic bearing compass instrument does the survey by using a traverse method of calculation. The survey is done mainly to make maps and plans for construction projects. The survey prevents projects from falling off the work in another land.

Types of Survey

Chain Surveying: In a small area if a flat is without any undulations, then chain surveying is used.

Principle of Compass Surveying

  1. The principle of surveys is traversed.
  2. The survey points are mainly as a series of lines. magnetic bearing of the compass instrument measure the survey
  3. The angle between the lines is measured by the compass instrument.
  4. The chain measures the length.
  5. The compass traversing is completed in two ways. One is an open traverse and the other one is a closed traverse.

Types of Compass

  1. Prismatic Compass.
  2. Surveyor Compass.

Prismatic Compass

This type of compass has many parts.

  1. Eye Vane: This is placed opposite to guide vane with an eye hole.
  2. Object Vane: This is placed opposite to eye vane. It bears a thin black wire to sight.
  3. Circular Metal Body (Dia 8 - 12 cm): This is the outer body layer of the instrument.
  4. Magnetic needle: It is the core of the instrument. It can Points towards North and South Pole.
  5. Graduated Circle Ring: It is used to measure the angle (0 - 360 degree).
  6. Glass Cover: It covers the instrument from dust and water.
  7. Pivot: placed at the center and supports the magnetic needle to move freely.
  8. Lifting Pin: It is placed below the guide vane.
  9. Reflecting Mirror: It is used to adjust the level of an object above or below the instrument level.
  10. SunGlasses: This is used when some bright objects intersect the view.

Adjustment of Prismatic Compass

Centering: The Prismatic Compass should be kept over the station where the bearing has to be measured. If it is not working then the user should use the tripods. By using this the bearing should be held over the peg.

Leveling: Users can adjust the instrument to a specific level by using the bubble tube.

Focusing: The prism must be moved up and down so that the aluminum ring is seen as clear, and focused.

Surveyor Compass

  1. Eye Vane: It is placed opposite to guide vane with an eye hole.
  2. Guide Vane: It is placed opposite to eye vane.
  3. Bubble Tube: It is used to place the instrument at a level.
  4. Magnetic needle: this is the core of the instrument. It points towards the North and South Pole.
  5. Graduated Circle Ring: Used to measure the angle (0 - 360 degree).
  6. Fixed Graduated Plane
  7. Adjustment Screw
  8. Circular Metal (Dia 8 - 10 cm): It is the outer body layer of the instrument.

Difference between the Prismatic Compass and Surveyor Compass

Prismatic Compass Surveyor Compass
When the prism & box in rotation, the magnetic needle & the graduate attached. when the dial is attached to the box, The magnetic needle would be free.
The graduations are provided in the clockwise direction, it is 0 to 360 degree. The graduations are divided into 4 parts. Each quadrant marked by 0 to 90-degree graduations.
The south end of the compass takes the readings through the eye-piece of the prism. The dial takes Reading directly through the north end of the needle.
The reading starts from the south end of the instrument. The reading starts from the north end of the instrument.
This is in the position of East & West constant. This is in the position of east & west interchanged.
The position of east & west is interchanged. The tripod is required to place the instrument.
You can get the whole circle bearing. You can get reduced bearing.

Error

  1. Instrumental Errors
  2. Personal Errors
  3. Nature Errors

Advantage of Compass Surveying

  1. The instrument is very easy to handle.
  2. Electrical power is not required.
  3. Compass surveying is very much preferable to retrace the old survey.
  4. Human resource is not required very much.

The Disadvantage of Compass Surveying

  1. The accuracy of the reading is not much precise.
  2. The instrument error happens frequently.
  3. An error can be happened due to the imperfection of the ranging rods or eyesight.

Sum Up

In this article, we discussed Types, principles of the survey, types of compass, advantages, disadvantages of compass surveying.

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For more information, please watch video tutorial

What's the difference between plain and geodetic surveying?

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