This document describes a new device for measuring tree trunk diameters called On-the-Fly Tree Caliper Measurement. The device uses structured laser lines and vision to measure tree trunks accurately as a vehicle moves, without needing precise positioning. It was tested indoors and outdoors on tree nurseries with errors of +/-1mm indoors and +/-2.5mm outdoors. Future work will focus on improving accuracy, testing at more locations, controlling measurement height, and reducing costs.

1. On-the-Fly Tree Caliper Measurement

2. On-the-Fly Tree Caliper Measurement Some caliper measurement systems Ultrasonic transducer – Upchurch et al. Infrared LEDs to measure tree trunk profile - Singh Laser scanner – Henning, Thies Laser and vision - Byrne Optical sensor, laser and motion measurement Delwiche Our approach Structured laser lines and vision

3. On-the-Fly Tree Caliper Measurement How does it work?

4. On-the-Fly Tree Caliper Measurement

5. On-the-Fly Tree Caliper Measurement Features of our tree caliper measurement device Accurate, reliable measurement Can be used under any lighting condition – such as in the field under sun light or at night or indoor at warehouse No precise position or movement required Can be attached to moving vehicle

6. On-the-Fly Tree Caliper Measurement Indoor testing at Adams County Nursery warehouse

7. On-the-Fly Tree Caliper Measurement Indoor testing – caliper estimate error

8. On-the-Fly Tree Caliper Measurement Outdoor testing at Eisler nursery in Prospect, PA

9. On-the-Fly Tree Caliper Measurement Outdoor testing – caliper estimate error

10. On-the-Fly Tree Caliper Measurement Conclusion +/- 2.5mm outdoor, +/- 1mm indoor Operating at any ambient lighting Mounted on moving vehicle Operating simultaneously with other tasks Counting trees while moving along Automatically databasing of tree caliper

11. On-the-Fly Tree Caliper Measurement Future and on going works Conducting large scale testing in nurseries in Washington, Oregon, California and Pennsylvania Improve accuracy of caliper measurement Increasing sample rate Controlling measuring height Improve algorithm of detecting edges of tree trunk Reducing cost of the device Improve laser safety