estimated Covariance
Gets estimated covariance matrix for estimated sensor parameters or null if not available. When bias or hard iron is known, diagonal elements of the covariance matrix contains variance for the following parameters (following indicated order): sx, sy, sz, mxy, mxz, myz, mzx, mzy. When bias or hard iron is not known, diagonal elements of the covariance matrix contains variance for the following parameters (following indicated order): bx, by, bz, sx, sy, sz, mxy, mxz, myx, myz, mzx, mzy, where bx, by, bz corresponds to bias or hard iron coordinates.