3D Digitising of Plants

There are several different approaches to measuring 3-D coordinates: articulated arms with sensors at the joints and systems which use sound, magnetism, light, lasers, arms + lasers or micropower-impulse radar. A guide to 3-D digitisers was published in the March 1995 edition of Computer Graphics World. Unfortunately, many of these systems are of limited use with plants because leaves and branches obscure line-of-sight from a point of observation to a point of interest on the plant. In the Insect Plant Interactions program, we are using Model GP12-XL (now known as the Freepoint 3D) digitisers made by the Science Accessories Division of GTCO Corporation in conjunction with special purpose software to gather information from which we build virtual plants.

Sonic digitiser: When the trigger of the gun is pulled, the processor (E) fires sound emitter A followed by emitter B. The processor converts into distances the time taken by sound to travel to each of the 3 microphones (D). These distances and the lengths AB and BC are used to calculate three-dimensional coordinates for the end of the pointer (C) whose line-of-sight to a microphone may be obscured by parts of the plant. The appropriate plant part labels and the associated coordinates are recorded by the portable computer (F).