Tree bark re-identification using a deep-learning feature descriptor

TL;DR

This paper introduces DeepBark, a deep-learning-based feature descriptor trained on a large bark image dataset, significantly improving tree bark re-identification accuracy over traditional methods, especially under challenging illumination conditions.

Contribution

The paper presents a novel data-driven descriptor, DeepBark, trained on a large bark image dataset, outperforming traditional descriptors like SIFT and SURF in re-identifying tree surfaces.

Findings

DeepBark achieves 87.2% mAP in bark image retrieval.

DeepBark outperforms SIFT and SURF descriptors.

Public dataset enables benchmarking of surface re-identification methods.

Abstract

The ability to visually re-identify objects is a fundamental capability in vision systems. Oftentimes, it relies on collections of visual signatures based on descriptors, such as SIFT or SURF. However, these traditional descriptors were designed for a certain domain of surface appearances and geometries (limited relief). Consequently, highly-textured surfaces such as tree bark pose a challenge to them. In turn, this makes it more difficult to use trees as identifiable landmarks for navigational purposes (robotics) or to track felled lumber along a supply chain (logistics). We thus propose to use data-driven descriptors trained on bark images for tree surface re-identification. To this effect, we collected a large dataset containing 2,400 bark images with strong illumination changes, annotated by surface and with the ability to pixel-align them. We used this dataset to sample from more than 2 million 64x64 pixel patches to train our novel local descriptors DeepBark and SqueezeBark. Our DeepBark method has shown a clear advantage against the hand-crafted descriptors SIFT and SURF. For instance, we demonstrated that DeepBark can reach a mAP of 87.2% when retrieving 11 relevant bark images, i.e. corresponding to the same physical surface, to a bark query against 7,900 images. Our work thus suggests that re-identifying tree surfaces in a challenging illuminations context is possible. We also make public our dataset, which can be used to benchmark surface re-identification techniques.