A Study on Trees's Knots Prediction from their Bark Outer-Shape

TL;DR

This study explores the use of deep learning, specifically CNN architectures, to predict internal knots in trees from external shape, aiming to replace costly CT-scanners and improve industrial wood processing efficiency.

Contribution

First application of CNNs to predict internal tree knots from external shape, demonstrating potential to replace expensive CT-scanners in industry.

Findings

CNNs can accurately predict knots distribution from external tree shape

Object detectors can automate knot labeling in CT images

Proposed methods are faster and cheaper than CT-scanners

Abstract

In the industry, the value of wood-logs strongly depends on their internal structure and more specifically on the knots' distribution inside the trees. As of today, CT-scanners are the prevalent tool to acquire accurate images of the trees internal structure. However, CT-scanners are expensive, and slow, making their use impractical for most industrial applications. Knowing where the knots are within a tree could improve the efficiency of the overall tree industry by reducing waste and improving the quality of wood-logs by-products. In this paper we evaluate different deep-learning based architectures to predict the internal knots distribution of a tree from its outer-shape, something that has never been done before. Three types of techniques based on Convolutional Neural Networks (CNN) will be studied. The architectures are tested on both real and synthetic CT-scanned trees. With these experiments, we demonstrate that CNNs can be used to predict internal knots distribution based on the external surface of the trees. The goal being to show that these inexpensive and fast methods could be used to replace the CT-scanners. Additionally, we look into the performance of several off-the-shelf object-detectors to detect knots inside CT-scanned images. This method is used to autonomously label part of our real CT-scanned trees alleviating the need to manually segment the whole of the images.