Compass Survey

What is the Compass Survey?

A survey that is mainly done with the help of a compass is called a compass survey.

Process of Compass Survey

A Compass device has a needle or rod. This rod has a magnet on its head. The rod can rotate comfortably on the pivot of the compass. No matter where it is rotating, it always looks for the direction of the wind. Or it is also called direction.
Compass surveying is done by using traversing. Traverse forming means connecting the points in the plot by means of a series of straight lines.
Major parts of a Prismatic Compass are:

  • Magnetic needle.
  • Graduated ring.
  • Adjustable mirror.
  • Sliding arrangement for the mirror.
  • Object vane.
  • Eye vane.
  • Metal box.
  • Glass cover.

Compass Survey

Compass surveying is surveying in which surveyors determine the position of an object’s location. They determine the angular measurements by a compass and linear measurements using a chain or tape. Compass survey is effective in the following circumstances:
Firstly, For a large surveying area, where chain surveying is not possible for surveying, therefore, compass surveying is an effective solution.
Secondly, The plot for surveying has numerous obstacles and undulations which prevent chaining.
And thirdly, If there is a time limit for surveying, compass surveying is usually adopted.

Places containing an iron core, power lines, etc, Compass survey is not possible there. Cause compass usually attracts magnets due to their natural properties and electromagnetic properties respectively. The traversing method is the process of Compass surveying. A traverse is formed by connecting the points in the plot by means of a series of straight lines.

Compass Survey

To find out the magnetic bearing of survey lines-We use the magnetic compass. There are two bearing system, One of them is the Whole Circle Bearing (W.C.B) system and another one is the Quadrantal Bearing (Q.B) system. It’s basically depends on the type of compass we are using. The basic principle of a magnetic compass is a strip of steel or iron which is magnetized and pivoted exactly at the center. As a result it can swing freely and then it can establish itself in the magnetic meridian at the place of arrangement.

Compass Survey

Major types of the magnetic compass are:

1. Prismatic compass
2. Surveyor’s compass
3. Level compass

Prismatic compass

Major parts of a Prismatic Compass are:

  • Magnetic needle
  • Graduated ring
  • Adjustable mirror
  • Sliding arrangement for mirror
  • Object vane
  • Eye vane
  • Metal box
  • Glass cover
  • Horsehair

There are two types of adjustments available for prismatic compass:

1. Temporary adjustment
2. Permanent adjustment

Temporary adjustments of prismatic compass

  • Centering: It is the process of fixing the compass exactly over the station. Centering is usually done by adjusting the tripod legs. Also, a plumb-bob is used to judge the accurate centering of instruments over the station.
  • Leveling: The instrument has to be leveled for use in hand or mounted over a tripod. For use in the hand, the graduated disc should swing freely and appears to be completely level in reference to the top edge of the case. on the other hand, using the tripod, they usually have a ball and socket arrangement for leveling purposes.
  • Focusing the prism: Prism can be slide up or down for focusing to make the readings clear and readable.

Permanent adjustments of prismatic compass

Same as the surveyor compass.