1. A method of controlling the factory of a drill string comprising: providing a steering behavior model having a build rate equation and a turn rate equation; calibrating the steering behavior model by minimising any variance between an actual build rate and an actual turn rate of a bottom-hole assembly generated by a first set of tool settings and a first estimated build rate and a first estimated turn rate generated by inputting the first set of tool settings into toe steering behavior model; determining an estimated position and an estimated azimuth and inclination data set of the bosom-hole assembly by inputting a second set of tool settings into the calibrated steering behavior model; comparing the estimated position and the estimated azimuth and inclination data set to a well plan to determine any deviation of the bottom-hole assembly therefrom; and determining a corrective action to correct the any deviation.