Measurement of cylindrical objects through laser telemetry: application to a new forest caliper

The feasibility of a new method for robust radius determination of cylindrical objects is studied. The principle is based on laser telemetry under structured lighting, where a laser plane creates a line on the object under test, which is observed by a charge coupled device camera. The novelty is in what we call the "three-tangents method" for the radius calculation. We show that this method is the most reliable one, taking into account the particular curve's characteristics. We mainly applied it to tree measurements in forests, for which a pre-prototype caliper was built. Experimental results are given. A general accuracy of 1% on 10-50-cm diameter trunks is claimed for distances up to 3.5 m.