Search results for "projection"
showing 10 items of 378 documents
Approximation of Feasible Parameter Set in worst case identification of block-oriented nonlinear models
2003
Abstract The estimation of the Feasible Parameter Set for block-oriented nonlinear models in a worst case setting is considered. A bounding procedure is determined both for polytopic and ellipsoidie sets, consisting in the projection of the FPS ⊂ R MN of the extended parameter vector onto suitable M or N-dimensional subspaces and in the solution of convex optimization problems which provide the extreme points of the Parameter Uncertainties Intervals of the model parameteres. Bounds obtained are tighter then in the previous approaches.
Which measures are projections of purely unrectifiable one-dimensional Hausdorff measures
2008
We give a necessary and sufficient condition for a measure p, on the real line to be an orthogonal projection of XAl for some purely 1-unrectifiable planar set A.
Future coastal hazard scenarios. A case study in NE Sicily (Italy)
2012
The coastal dynamics is the result of several causes that contribute to change the balance of beach deposits over time. The beach system is not always able to maintain coastal balance: the factors contributing to this phenomenon are to be found in both natural and anthropogenic spheres. In this context we present the analysis of marine geology and coastal geomorphological data of a sector between Rocca di Caprileone and Tindari (north-eastern Sicily) with the aim to: i) determine their onland-offshore area relationships, ii) analyze which natural features may contribute to coastal retreat, iii) present coastal hazard scenarios. Until fifty years ago the natural balance of this coastal area …
Fast adaptive frame preprocessing for 3D reconstruction
2015
Abstract: This paper presents a new online preprocessing strategy to detect and discard ongoing bad frames in video sequences. These include frames where an accurate localization between corresponding points is difficult, such as for blurred frames, or which do not provide relevant information with respect to the previous frames in terms of texture, image contrast and non-flat areas. Unlike keyframe selectors and deblurring methods, the proposed approach is a fast preprocessing working on a simple gradient statistic, that does not require to compute complex time-consuming image processing, such as the computation of image feature keypoints, previous poses and 3D structure, or to know a prio…
Pedestrian Tracking in 360 Video by Virtual PTZ Cameras
2018
Since the data acquired by a PTZ camera change while adjusting the pan, tilt and zoom parameters, the results of tracking algorithms are difficult to reproduce; such diffi- culty limits the development and the comparison of tracking algorithms with PTZ cameras. The recently introduced 360- degree cameras acquire spherical views of the environment, generally stored as equirectangular images. Each pixel of an equirectangular image corresponds to a point on the spherical surface. A gnomonic projection can be used to project the points on the spherical surface onto a plane tangent to the sphere. Such tangent plane can be interpreted as the image plane of a virtual PTZ camera oriented towards th…
Piecewise planar underwater mosaicing
2015
A commonly ignored problem in planar mosaics, yet often present in practice, is the selection of a reference homography reprojection frame where to attach the successive image frames of the mosaic. A bad choice for the reference frame can lead to severe distortions in the mosaic and can degenerate in incorrect configurations after some sequential frame concatenations. This problem is accentuated in uncontrolled underwater acquisition setups as those provided by AUVs or ROVs due to both the noisy trajectory of the acquisition vehicle — with roll and pitch shakes — and to the non-flat nature of the seabed which tends to break the planarity assumption implicit in the mosaic construction. These…
A Programmable Networked Processing Node for 3D Brain Vessels Reconstruction
2011
Real-time 3D imaging represents a developing trend in medical imaging. However, most of the 3D medical imaging algorithms are computationally intensive. In this paper, a programmable networked node for 3D brain vessels reconstruction is proposed. Starting from 2D PC-MRA (Phase-Contrast Magnetic Resonance Angiography) sequences, the node is able to generate the 3D brain vasculature using the MIP (Maximum Intensity Projection) algorithm. The node has been prototyped on the Celoxica RC203E board, equipped with a Virtex II FPGA, to get the advantages of an hardware implementation, reaching a better throughput with respect to analogous software implementations. Its generality and programmable ca…
360° Tracking Using a Virtual PTZ Camera
2017
Object tracking using still or PTZ cameras is a hard task for large spaces and needs several devices to completely cover the area or to track multiple subjects. The introduction of \(360^{\circ }\) camera technology offers a complete view of the scene in a single image and can be useful to reduce the number of devices needed in the tracking problem. In this paper we present a framework using \(360^{\circ }\) cameras to simulate an unlimited number of PTZ cameras and to be used for tracking. The proposed method to track a single target process an equirectangular view of the scene and obtains a model of the moving object in the image plane. The target is tracked analyzing the next frame of th…
Drawing
2020
A drawing is the result of the production of marks on a surface with suitable means to represent a scene, concrete or abstract objects for technological, scientific, artistic, communicative aims. Some theories claimed that drawing is founded on symbolic systems that are culture-dependent. Evidence has been found that the ability of recognizing what drawings represent is widespread across ages, cultures and species. Drawing may be founded on shared cognitive capacities. These capacities can be abstractly described as the graphic and the denotation system.