An improved four roller tree harvester head preferably includes a tower frame, a saw box, a delimb box, a four roller assembly, a slewing ring and a boom bracket. The saw box is mounted to a bottom of the tower frame and the delimb box is mounted to a top of the tower frame. Hydraulic hoses and electrical lines are routed through the boom bracket, slewing ring and tower frame to a hydraulic valve block. Hydraulic hoses may be attached to a rotary union. An actuation cylinder of the four roller assembly includes a linear positioning sensor, which provides an output to an electronic controller, which calculates a diameter of a tree. The four roller assembly includes at least one rotation encoder, which provides an output to the electronic controller about the length of a tree. An independent measurement wheel measures a length of the tree through the electronic controller.
