A basic, reliable model, the BL7 ALTIMeter features a single release button and indicator. To begin the calculation of tree height, use a measuring tape or rangefinder (not included) to determine baseline distance. Next, target the uppermost point of the tree. Read and record the measured value. Press the release button to free the pendulum and measure the lowermost point. The measured values of the uppermost and lowermost points are then used to determine actual height.