1. A method of controlling the trajectory of a drill string comprising: providing a steering behavior model having a build rate equation and a turn rate equation of a bottom hole assembly; calibrating the steering behavior model by minimizing any variance between an actual build rate and an actual turn rate of the 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 the steering behavior model; determining a first estimated position of the bottom-hole assembly by inputting a second set of tool settings into the calibrated steering behavior model; comparing the first estimated position to a well plan to determine any deviation of the bottom-hole assembly from the well plan; and utilizing an inverse of the steering behavior model to generate a third set of tool settings that are predicted to result in a second estimated position.