Showing posts from September, 2012

Local Attraction - Compass Surveying

Hello, Local Attraction:  A compass shows the direction of the magnetic meridian on the principle of magnetism. Any magnet attracting  material, when is brought near to the compass needle, needle will deflect from the true magnetic north.
In that case, you will not read the true north direction and if you take the bearings of the lines in such condition there comes a error in the readings and that error is known as the local attraction.
Materials which are most likely to be present there, while you are doing the compass surveying, are such as an iron chain, metallic wrist band or ear rings(metallic) that one might be wearing.
Other things such as an electric pole or electric wires may also produce local attraction. The needle is attracted to these objects, so this will deviate from the true direction of the magnetic meridian. If local attraction is available at a station then all the readings taken from that station will have the same amount of the error, and we have to correct the reading…