The plane of the coild of tangent galvanometer is parallel to the magnetic meridian

The plane of the coil of tangent galvanometer is kept parallel to magnetic meridian to

Before using tangent galvanometer for the measurement of current, why is the plane of coil of tangent galvanometer set in the magnetic meridian?

Before using tangent galvanometer for the measurement of current, why is the plane of coil of tangent galvanometer set in the magnetic meridian?

The tangent galvanometer is set into magnetic meridian

Define magnetic meridian.