A vehicle guidance system 11 including a stepper motor 50 is provided. The system 11 comprises a hydraulic steering cylinder 21 for controlling a steering angle of a steerable wheel 30 of a vehicle. A hydraulic steering valve 52 is adapted to control a flow of hydraulic fluid to the hydraulic steering cylinder 21. A stepper motor 50 is adapted to move or modulate a shaft 53 coupled to the hydraulic steering valve 52 in accordance with a control signal or control data message from a vehicle guidance controller 44. A position encoder 66 of the stepper motor 50 can measure the movement of the shaft 53. A steering angle estimator 68 can estimate the steering angle based on measurements of the position encoder 66. A location-determining receiver 64 provides position data and heading data. The vehicle guidance controller 44 provides the control signal or control data message based on the estimated steering angle, position data and heading data.
