1. A method of payload estimation of weight bearing machinery, the method comprising the steps of: (a) creating a series of Kalman filter approximations to the weight bearing machinery, each approximation representing a system model of the weight bearing machinery having distinct levels of payload; (b) determining from said series an overall approximation of the current operating parameters of the weight bearing machinery; and, (c) utilizing the parameters derived from said step (b) to determine an estimated payload of said weight bearing machinery.