Abstract: An apparatus for measuring and storing a tree characteristic that preferably is tree diameter and other data related to location, variety and grade of a tree being measured. The apparatus has a handle, a wand extending therefrom, and a measurement head carried by the wand for measuring diameter. The wand has a control handle connected by a cable to a movable caliper jaw carried by the head to measure a diameter of a tree between the movable jaw and another jaw. A vernier having measurement locator slots and a home position slot is carried by the cable and communicates with slot sensors that send signals to an on-board computer to determine direction and distance of jaw movement for enabling the distance between the jaws to be determined. Two optoisolators and the computer comprise a jaw motion and direction detecting quadrature detector. A third optoisolator detects when the movable jaw is in its home position.