Compass Surveying

In the field of compass surveying the direction and orientation of survey line measured by a compass and also their lengths by chaining or taping directly on the surface of the earth, is defined as Compass surveying.

 

Generally Surveying Compass are two types,

  • Prismatic Compass

The different parts of prismatic compass are as follows.

  1. Compass box
  2. Lifting Lever
  3. Needle

This single needle is of edge bar type and it also acts as an index marker.

  1. Agate Cap
  2. Glass Cover
  3. Sunglass
  4. Prism
  5. Eye vane
  6. Focussing stud
  7. Brake pin
  8. Spring brake
  9. Lifting Pin
  10. Objective vane

The vanes is consists of metal vane with a vertical hair line.

  1. Adjustable mirror
  2. Prism Cap
  3. Graduated ring

This ring is attached to the box and not to the needle. This graduated ring rotates along with the line of sight. The  graduations are in Q.B system having 0o at North and South and 90o at East and West are interchangeable.

  1. Pivot

The compass reading are taken directly by seeing through the top of the glass .Slighting and reading cannot be done simultaneously from one position of the observer. The instrument must be used with tripod.

  • Surveyor Compass

The different parts of Surveyor compass are as follows.

  1. Box
  2. Lifting lever
  3. Pivot
  4. Circular Graduated arc This ring is attached to the box and not to the needle. This graduated ring rotates along with the line of sight. The graduations are in W.C.B system having 0o at South , 90o at West , 180o North and 270o
  5. Glass top
  6. Sight vanes

The object vanes consists of a metal vane with a vertical hair line. The eye vane consists of a metal vane with a slit.

  1. Jewel bearings
  2. Lifting pin
  3. Magnetic needle

The needle is broad type of needle and does not act as an index.

  1. Rider
  2. Metal pin

The readings are taken with the help of prism and eye slit. The slighting  and reading can be done simultaneously from one position of the observer. Tripod stand may be or may not be provided . The instrument may be used even by holding by hand.