What is local attraction in land surveying?

Local attraction & Compass Surveying Local attraction is the phenomenon by which the magnetic needle is constantly prevented to point towards the magnetic north at a place.

What is local attraction in survey?

While compass surveying, the magnetic needle is sometimes disturbed from its normal position under the influence of external attractive forces. Such a disturbing influence is called as local attraction.

What is local attraction & Correction of bearing?

ADVERTISEMENTS: (ii) The observed bearings are corrected by applying correction to the stations affected by the local attraction. For this, error at each of the station is found and then starting from an unaffected bearing, the bearings of the successive lines are adjusted by applying corrections to them.

What is local attraction?

Local attraction is the phenomenon by which the magnetic needle is constantly prevented to point towards the magnetic north at a place.

What are the source of local attraction?

Some of the sources of local attraction are : magnetite in the ground, wire carrying electric current, steel structures, railroad rails, underground iron pipes, keys, steel bowed spectacles, metal buttons, axes, chains, steel tapes etc., which may be lying on the ground nearby. Detection of local attraction.

Which is local attraction in compass survey?

This prevents the needle from pointing correctly towards the magnetic north & creates an error. Such a disturbing influence of external forces or objects over the compass needle is said to be a local attraction. 2.

What is bearing in survey?

In land surveying, a bearing is the clockwise or counterclockwise angle between north or south and a direction. For example, bearings are recorded as N57°E, S51°E, S21°W, N87°W, or N15°W.

What is RL in surveying?

From Wikipedia, the free encyclopedia. Relative level in surveying refers to equating elevations of survey points with reference to a common assumed datum. It is a vertical distance between survey point and adopted datum plane.

What is FB and BB in surveying?

Bearings measured in the direction of progress of the survey are known as fore bearing and bearings measured opposite to the direction of the survey are known as back bearing.

How many types of bearing are there in survey?

Types of bearings used in land navigation

There are four types of bearings most commonly used in land navigation: true bearings. grid bearings. magnetic bearings.

What is azimuth in survey?

What is Azimuth in Surveying? Azimuths are defined as horizontal angles that are measured from the reference meridian in the clockwise direction. Azimuths are also called a whole circle bearing system(W.C.B). Azimuths are used in compass surveying, plane surveying, where it is generally measured from the north.

What is magnetic compass bearing?

If you are taking a bearing off a real point on the landscape with a compass, you are using your compass to measure the angle clockwise from magnetic north to this point on the landscape. This is called a magnetic bearing. Remember that the bearing is measured clockwise.

What is Quadrantal bearing?

A horizontal angle or bearing less than 90 degrees , measured to north, south, east, or west from a survey line.

How many meridians are used in survey?

How many meridians are used in surveying? Explanation: True, magnetic and arbitrary meridians are used. True meridian passes through true North and South.

What is WCB and RB?

When Whole Circle Bearing(W.C.B) lies between 0° to 90°. Reduced Bearing(R.B) = W.C.B.

What is WCB and RB in surveying?

In Whole Circle Bearing – Bearings are measured clockwise from north of reference meridian; In Reduced Bearing – Bearings are measured either clockwise or anti-clockwise from north/south whichever is close to the line.

What is Surveyors compass?

The surveyor’s compass (Fig. 11) is an instrument for determining the horizontal direction of a line with reference to the direction of a magnetic needle. The needle is balanced at its center on a “pivot” so that it swings freely in a horizontal plane.

How do you find WCB?

Whole Circle Bearing Formula

Just measure the angle between true north line to the survey line to find the WCB . Don’t forget to measure the clockwise angle in determining the whole circle bearing. If a survey line falls in the first quadrant, its WCB varies from 0° to 90°.

What is WCB system?

The horizontal angle made by the survey line with the magnetic north in the clockwise direction is the whole circle bearing (WCB) of that line. This system is also known as the azimuthal system.

What is difference between WCB and QB in surveying?

The horizontal angle made by a line with the magnetic north in the clockwise direction is the whole circle bearing of the line. Only the magnetic north line is considered as reference line in whole circle bearing system. Both magnetic north and south lines are considered as reference line in quadrantal bearing system.

What is forward bearing?

*Fore bearing is the bearing of the line in the forward direction of surveying. *The formula used to calculate the fore bearing of the progressive line F.B = B.B ± 180° { + sign when B.B less than 180° and – sign when B.B more than 180°}.