61 research outputs found
Fast and robust curve skeletonization for real-world elongated objects
We consider the problem of extracting curve skeletons of three-dimensional,
elongated objects given a noisy surface, which has applications in agricultural
contexts such as extracting the branching structure of plants. We describe an
efficient and robust method based on breadth-first search that can determine
curve skeletons in these contexts. Our approach is capable of automatically
detecting junction points as well as spurious segments and loops. All of that
is accomplished with only one user-adjustable parameter. The run time of our
method ranges from hundreds of milliseconds to less than four seconds on large,
challenging datasets, which makes it appropriate for situations where real-time
decision making is needed. Experiments on synthetic models as well as on data
from real world objects, some of which were collected in challenging field
conditions, show that our approach compares favorably to classical thinning
algorithms as well as to recent contributions to the field.Comment: 47 pages; IEEE WACV 2018, main paper and supplementary materia
Shape from inconsistent silhouette: Reconstruction of objects in the presence of segmentation and camera calibration error
Silhouettes are useful features to reconstruct the object shape when the object is textureless or the shape classes of objects are unknown. In this dissertation, we explore the problem of reconstructing the shape of challenging objects from silhouettes under real-world conditions such as the presence of silhouette and camera calibration error. This problem is called the Shape from Inconsistent Silhouettes problem. A psuedo-Boolean cost function is formalized for this problem, which penalizes differences between the reconstruction images and the silhouette images, and the Shape from Inconsistent Silhouette problem is cast as a psuedo-Boolean minimization problem. We propose a memory and time efficient method to find a local minimum solution to the optimization problem, including heuristics that take into account the geometric nature of the problem. Our methods are demonstrated on a variety of challenging objects including humans and large, thin objects. We also compare our methods to the state-of-the-art by generating reconstructions of synthetic objects with induced error. ^ We also propose a method for correcting camera calibration error given silhouettes with segmentation error. Unlike other existing methods, our method allows camera calibration error to be corrected without camera placement constraints and allows for silhouette segmentation error. This is accomplished by a modified Iterative Closest Point algorithm which minimizes the difference between an initial reconstruction and the input silhouettes. We characterize the degree of error that can be corrected with synthetic datasets with increasing error, and demonstrate the ability of the camera calibration correction method in improving the reconstruction quality in several challenging real-world datasets
Multispecies Fruit Flower Detection Using a Refined Semantic Segmentation Network
In fruit production, critical crop management decisions are guided by bloom intensity, i.e., the number of flowers present in an orchard. Despite its importance, bloom intensity is still typically estimated by means of human visual inspection. Existing automated computer vision systems for flower identification are based on hand-engineered techniques that work only under specific conditions and with limited performance. This letter proposes an automated technique for flower identification that is robust to uncontrolled environments and applicable to different flower species. Our method relies on an end-to-end residual convolutional neural network (CNN) that represents the state-of-the-art in semantic segmentation. To enhance its sensitivity to flowers, we fine-tune this network using a single dataset of apple flower images. Since CNNs tend to produce coarse segmentations, we employ a refinement method to better distinguish between individual flower instances. Without any preprocessing or dataset-specific training, experimental results on images of apple, peach, and pear flowers, acquired under different conditions demonstrate the robustness and broad applicability of our method
Segmenting root systems in X-ray computed tomography images using level sets
The segmentation of plant roots from soil and other growing media in X-ray
computed tomography images is needed to effectively study the root system
architecture without excavation. However, segmentation is a challenging problem
in this context because the root and non-root regions share similar features.
In this paper, we describe a method based on level sets and specifically
adapted for this segmentation problem. In particular, we deal with the issues
of using a level sets approach on large image volumes for root segmentation,
and track active regions of the front using an occupancy grid. This method
allows for straightforward modifications to a narrow-band algorithm such that
excessive forward and backward movements of the front can be avoided, distance
map computations in a narrow band context can be done in linear time through
modification of Meijster et al.'s distance transform algorithm, and regions of
the image volume are iteratively used to estimate distributions for root versus
non-root classes. Results are shown of three plant species of different
maturity levels, grown in three different media. Our method compares favorably
to a state-of-the-art method for root segmentation in X-ray CT image volumes.Comment: 11 page
Automatic Segmentation of Trees in Dynamic Outdoor Environments
Segmentation in dynamic outdoor environments can be difficult when the illumination levels and other aspects of the scene cannot be controlled. Specifically in orchard and vineyard automation contexts, a background material is often used to shield a camera\u27s field of view from other rows of crops. In this paper, we describe a method that uses superpixels to determine low texture regions of the image that correspond to the background material, and then show how this information can be integrated with the color distribution of the image to compute optimal segmentation parameters to segment objects of interest. Quantitative and qualitative experiments demonstrate the suitability of this approach for dynamic outdoor environments, specifically for tree reconstruction and apple flower detection application
The Use of Agricultural Robots in Orchard Management
Book chapter that summarizes recent research on agricultural robotics in
orchard management, including Robotic pruning, Robotic thinning, Robotic
spraying, Robotic harvesting, Robotic fruit transportation, and future trends.Comment: 22 page
Detecting Invasive Insects with Unmanned Aerial Vehicles
A key aspect to controlling and reducing the effects invasive insect species
have on agriculture is to obtain knowledge about the migration patterns of
these species. Current state-of-the-art methods of studying these migration
patterns involve a mark-release-recapture technique, in which insects are
released after being marked and researchers attempt to recapture them later.
However, this approach involves a human researcher manually searching for these
insects in large fields and results in very low recapture rates. In this paper,
we propose an automated system for detecting released insects using an unmanned
aerial vehicle. This system utilizes ultraviolet lighting technology, digital
cameras, and lightweight computer vision algorithms to more quickly and
accurately detect insects compared to the current state of the art. The
efficiency and accuracy that this system provides will allow for a more
comprehensive understanding of invasive insect species migration patterns. Our
experimental results demonstrate that our system can detect real target insects
in field conditions with high precision and recall rates.Comment: IEEE ICRA 2019. 7 page
Apple Flower Detection Using Deep Convolutional Networks
To optimize fruit production, a portion of the flowers and fruitlets of apple trees must be removed early in the growing season. The proportion to be removed is determined by the bloom intensity, i.e., the number of flowers present in the orchard. Several automated computer vision systems have been proposed to estimate bloom intensity, but their overall performance is still far from satisfactory even in relatively controlled environments. With the goal of devising a technique for flower identification which is robust to clutter and to changes in illumination, this paper presents a method in which a pre-trained convolutional neural network is fine-tuned to become specially sensitive to flowers. Experimental results on a challenging dataset demonstrate that our method significantly outperforms three approaches that represent the state of the art in flower detection, with recall and precision rates higher than 90%. Moreover, a performance assessment on three additional datasets previously unseen by the network, which consist of different flower species and were acquired under different conditions, reveals that the proposed method highly surpasses baseline approaches in terms of generalization capability
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