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Azhar Shahzad

Types of Meridian and Bearings

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Meridian

Meridian is a reference direction with respect to which the direction of lines are mentioned. There are three types of meridian - True Meridian, Magnetic Meridian & Arbitrary Meridian

1 - True Meridian

It is the reference direction of north pole of earth from a given station point. It is also called geographic meridian.

2 - Magnetic Meridian

It is the direction of north pole indicated by magnetic needle.

3 - Arbitrary Meridian

This is any assume direction to a well defined object. It may be useful for small areas. e.g A mosque is taken as reference and location of road will be mentioned with respect to this mosque. Direction of magnetic north with respect to true north is called magnetic direction.

Bearings

Bearing is the angle which a certain line make with a certain a certain meridian. Bearing with respect to true meridian is called true bearings while magnetic bearing is the angle which a line makes with respect to magnetic meridian. There are two ways to represent the bearings,

  • Whole circle bearing (W.C.B)
  • Reduced Bearing (R.B)

1) Whole Circle Bearing (W.C.B)

It can be taken 0° to 360°. Quadrants are taken clock-wisely and angles are also determined in clockwise direction.

2) Reduced Bearing

Reduced bearing or Quadrantal bearing is the angle which a line makes from North or South Pole whichever may be near. It is value is from 0° to 90°.

post-1-0-20743200-1426529218_thumb.jpg

Using the above figures you can easily convert the Whole Circle Bearing into Reduced Bearing. Some Examples are given are below.

Whole Circle Bearing (W.C.B) Reduced Bearing (R.B)
135° S45E
37° N37E
65° N65E
125° S55E
215° S35W
300° N60W

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On 5/24/2016 at 2:54 AM, Guest Anandh said:

if whole circle bearing of line 270°, then reduced bearing of the line is?

reduced bearing N90W or S90W

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On 5/24/2016 at 11:54 AM, Guest Anandh said:

if whole circle bearing of line 270°, then reduced bearing of the line is?

The direction will be exactly towards west. Hence, no reduced bearing in this case.

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