56,625 research outputs found
Difference of Normals as a Multi-Scale Operator in Unorganized Point Clouds
A novel multi-scale operator for unorganized 3D point clouds is introduced.
The Difference of Normals (DoN) provides a computationally efficient,
multi-scale approach to processing large unorganized 3D point clouds. The
application of DoN in the multi-scale filtering of two different real-world
outdoor urban LIDAR scene datasets is quantitatively and qualitatively
demonstrated. In both datasets the DoN operator is shown to segment large 3D
point clouds into scale-salient clusters, such as cars, people, and lamp posts
towards applications in semi-automatic annotation, and as a pre-processing step
in automatic object recognition. The application of the operator to
segmentation is evaluated on a large public dataset of outdoor LIDAR scenes
with ground truth annotations.Comment: To be published in proceedings of 3DIMPVT 201
Object Recognition in Noisy RGB-D Data
The object recognition task on 3D scenes is a growing research field that faces some problems relative to the use of 3D point clouds. In this work, we focus on dealing with noisy clouds through the use of the Growing Neural Gas (GNG) network filtering algorithm. Another challenge is the selection of the right keypoints detection method, that allows to identify a model into a scene cloud. The GNG method is able to represent the input data with a desired resolution while preserving the topology of the input space. Experiments show how the introduction of the GNG method yields better recognitions results than others filtering algorithms when noise is present.The object recognition task on 3D scenes is a growing research field that faces some problems relative to the use of 3D point clouds. In this work, we focus on dealing with noisy clouds through the use of the Growing Neural Gas (GNG) network filtering algorithm. Another challenge is the selection of the right keypoints detection method, that allows to identify a model into a scene cloud. The GNG method is able to represent the input data with a desired resolution while preserving the topology of the input space. Experiments show how the introduction of the GNG method yields better recognitions results than others filtering algorithms when noise is present
On the feedback from super stellar clusters. I. The structure of giant HII regions and HII galaxies
We review the structural properties of giant extragalactic HII regions and
HII galaxies based on 2D hydrodynamic calculations, and propose an evolutionary
sequence that accounts for their observed detailed structure. The model assumes
a massive and young stellar cluster surrounded by a large collection of clouds.
These are thus exposed to the most important star-formation feedback
mechanisms: photoionization and the cluster wind. The models show how the two
feedback mechanisms compete in the disruption of clouds and lead to two
different hydrodynamic solutions: The storage of clouds into a long lasting
ragged shell that inhibits the expansion of the thermalized wind, and the
steady filtering of the shocked wind gas through channels carved within the
cloud stratum. Both solutions are claimed to be concurrently at work in giant
HII regions and HII galaxies, causing their detailed inner structure. This
includes multiple large-scale shells, filled with an X-ray emitting gas, that
evolve to finally merge with each other, giving the appearance of shells within
shells. The models also show how the inner filamentary structure of the giant
superbubbles is largely enhanced with matter ablated from clouds and how cloud
ablation proceeds within the original cloud stratum. The calculations point at
the initial contrast density between the cloud and the intercloud media as the
factor that defines which of the two feedback mechanisms becomes dominant
throughout the evolution. Animated version of the models can be found at
http://www.iaa.csic.es/\~{}eperez/ssc/ssc.html.Comment: 28 pages, 10 figures, accepted for publication in the ApJ. Animated
version of the models can be found at
http://www.iaa.csic.es/\~{}eperez/ssc/ssc.htm
Detection of a new, low-brightness supernova remnant possibly associated with EGRET sources
We report on the discovery of a shell-type supernova remnant in the southern
sky. It is a large (8*8), low-brightness source with a nonthermal radio
spectrum, which requires background filtering to isolate it from the diffuse
background emission of the Galaxy. Three 3EG gamma-ray sources are spatially
correlated with the radio structure. We have made 21-cm line observations of
the region and found that two of these sources are coincident with HI clouds.
We propose that the gamma-ray emission is the result of hadronic interactions
between high-energy protons locally accelerated at the remnant shock front and
atomic nuclei in the ambient clouds.Comment: 6 pages, 5 figure
Ground Profile Recovery from Aerial 3D LiDAR-based Maps
The paper presents the study and implementation of the ground detection
methodology with filtration and removal of forest points from LiDAR-based 3D
point cloud using the Cloth Simulation Filtering (CSF) algorithm. The
methodology allows to recover a terrestrial relief and create a landscape map
of a forestry region. As the proof-of-concept, we provided the outdoor flight
experiment, launching a hexacopter under a mixed forestry region with sharp
ground changes nearby Innopolis city (Russia), which demonstrated the
encouraging results for both ground detection and methodology robustness.Comment: 8 pages, FRUCT-2019 conferenc
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