A positioning system 100 for a boom having right and left boom arms, the system comprising: a first actuator 50 for moving the right boom arm relative to a support frame； a second actuator for moving the left boom arm relative to a support frame； a first hydraulic link 60 between the actuators such that as one actuator extends, the other retracts； and a hydraulic control device 61 for controlling movement of hydraulic fluid within the hydraulic link, thereby controlling the extension and/or retraction of the first and second actuators. The system may comprise a third actuator (130 figure 7) that is connected to the hydraulic link which controllably determines the extension and retraction of the left and right actuators. The actuators may be linked by a second hydraulic link 69.
