1. A method for detecting operator alertness of an operator of a vehicle or machine, the method comprising: collecting reference position data associated with the operator when the operator is in an alert state, wherein the collecting reference position data comprises creating a three dimensional representation of the operator, or a portion thereof, via stereo vision processing; determining observed position data of one or more reference points of the three dimensional representation of the operator, or the portion thereof, during a time interval; and sending an alert signal to alert the operator if a detected angular shift of the one or more reference points of the three dimensional representation exceed a displacement threshold.