#Blub
What is local attraction & Correction of bearing?
The deflection of a magnetic needle from its true position due to the presence of magnetic influencing material such as iron ore, magnetic rock, underground pipeline, electric cables, iron pipes, electric poles in its vicinity is called “Local Attraction”.
How is local attraction calculated?
Local attraction & Compass Surveying

The occurrence of local attraction can be detected by observing the difference between the fore and back bearings. If there is no influence of local attraction and other error, this difference will be 180. So we can then conclude that both stations are free from local attraction.

What is magnetic declination in surveying?
At most places on the Earth's surface, the compass doesn't point exactly toward geographic north. The deviation of the compass from true north is an angle called "declination" (or "magnetic declination").

What are the four cardinal directions?
North, east, south, and west are the four cardinal directions, often marked by the initials N, E, S, and W. East and west are at right angles to north and south. East is in the clockwise direction of rotation from north.


Do I add or subtract magnetic variation?
Magnetic versus True

Use this mnemonic to remember that with variation west, the magnetic direction is going to be "best" or greater than true. Variation is added to true to arrive at magnetic, or subtracted from magnetic to get true. With variation east, magnetic will be "least" or less than true.

What are the 32 compass points?
Compass point names

The names of the 32-wind compass rose follow these rules: - The cardinal directions are North (N), East (E), South (S), West (W), at 90° angles on the compass rose.

What is the middle of a compass called?
A compass rose, sometimes called a windrose or rose of the winds, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions (north, east, south, and west) and their intermediate points.

свернуть