A method for adjusting a drilling parameter of a drill string includes: determining one or more modes of the drill string; sensing a first oscillation amplitude at a first position in the drill string and/or an oscillation parameter of the drill string at the first position or a second position to provide measured first oscillation amplitude data and/or measured oscillation parameter data; identifying a mode of the drill string using one or more determined modes and a stability criterion and at least one of the measured first oscillation amplitude data and the measured oscillation parameter data; calculating an oscillation amplitude at a position of interest in the drill string using the identified mode and at least one of the measured first oscillation amplitude data, the measured oscillation parameter data and the stability criterion; and adjusting the drilling parameter in response to the calculated oscillation amplitude at the position of interest.