Search results for "Homograph"
showing 10 items of 15 documents
Homography based egomotion estimation with a common direction
2017
International audience; In this paper, we explore the different minimal solutions for egomotion estimation of a camera based on homography knowing the gravity vector between calibrated images. These solutions depend on the prior knowledge about the reference plane used by the homography. We then demonstrate that the number of matched points can vary from two to three and that a direct closed-form solution or a Gröbner basis based solution can be derived according to this plane. Many experimental results on synthetic and real sequences in indoor and outdoor environments show the efficiency and the robustness of our approach compared to standard methods.
Finite linear spaces in which any n-gon is euclidean
1986
Abstract An n-gon of a linear space is a set S of n points no three of which are collinear. By a diagonal point of S we mean a point p off S with the property that at least two lines through p intersect S in two points. The number of diagonal points is called the type of S. For example, a 4-gon has at most three diagonal points. We call an n-gon euclidean if (roughly speaking) it contains the maximal possible number of 4-gons of type 3. In this paper, we characterize all finite linear spaces in which, for a fixed number n ⩾ 5, any n-gon is euclidean. It turns out that these structures are essentially projective spaces or punctured projective spaces.
A New Method to Measure 3D Textile Defects by Using Dual-lens Camera
2013
International audience; Industrial textile fabric with functionalization always has a high standard requirement. Take polytetrafluoroethylene (PTFE) conveyor belt as an example, the base fabrics must be of first-rate quality, with no weaving faults or broken fibers on coated surface [1]. In a previous work, we have proposed an original method to measure the height of the fiber based on variable homography. This measurement is based on a single camera acquiring two successive frames. This scheme is working well, but measurement depends on conveyor speed used for scrolling fabric. In this paper, we propose an improvement by using a new acquisition device based on two mini-lenses assembled as …
Estimating the Best Reference Homography for Planar Mosaics From Videos
2015
This paper proposes a novel strategy to find the best reference homography in mosaics from video sequences. The reference homography globally minimizes the distortions induced on each image frame by the mosaic homography itself. This method is designed for planar mosaics on which a bad choice of the first reference image frame can lead to severe distortions after concatenating several successive homographies. This often happens in the case of underwater mosaics with non-flat seabed and no georeferential information available. Given a video sequence of an almost planar surface, sub-mosaics with low distortions of temporally close image frames are computed and successively merged according to…
Exploring the sense distributions of homographs
2006
This paper quantitatively investigates in how far local context is useful to disam-biguate the senses of an ambiguous word. This is done by comparing the co-occurrence frequencies of particular context words. First, one context word representing a certain sense is chosen, and then the co-occurrence frequencies with two other context words, one of the same and one of another sense, are compared. As expected, it turns out that context words belonging to the same sense have considerably higher co-occurrence frequencies than words belonging to different senses. In our study, the sense inventory is taken from the University of South Florida homograph norms, and the co-occurrence counts are based…
I saw this somewhere else: the Spanish Ambiguous Words (SAW) database
2017
The present paper describes the Spanish Ambiguous Words (SAW) database, which comprises 210 words (133 polysemous and 77 homographs). Three-hundred and fifteen Spanish university students took part in the study on which SAW is based. First, subjective word meanings and senses were collected by means of a meaning retrieval task. Two judges then assigned participants’ responses to different categories of meaning according to lexicographical and statistical criteria. Results showed that, while there was a relatively high relationship between the number of senses included in the dictionary and those provided by participants (r = .62), regression analyses on lexical decision and naming times rev…
A homography formulation to the 3pt plus a common direction relative pose problem
2014
International audience; In this paper we present an alternative formulation for the minimal solution to the 3pt plus a common direction relative pose prob-lem. Instead of the commonly used epipolar constraint we use the homog-raphy constraint to derive a novel formulation for the 3pt problem. This formulation allows the computation of the normal vector of the plane defined by the three input points without any additional computation in addition to the standard motion parameters of the camera. We show the working of the method on synthetic and real data sets and compare it to the standard 3pt method and the 5pt method for relative pose estima-tion. In addition we analyze the degenerate condi…
DEFINITION ET ETUDE DES PERFORMANCES D'UN DETECTEUR DE STRUCTURES CURVILINEAIRES. APPLICATION A LA STEREOSCOPIE ET LA DETECTION D'OBJETS FILAIRES
2008
The work presented in this paper falls under the domain of matching. In this context, we try to show the interest of using the curvilinear regions in order to enhance the global performance of various matching applications. A brand new detector for curvilinear regions is introduced (CRD), along with the specific curvilinear regions descriptor (CRD) required. Performance evaluations were done in two parts: First, we evaluated and compared the segmentations performances of our detector, in particular on a retina vessels segmentation application. And second, we estimated the matching performances using K. Mykolajczyk toolkit. This methodology helps obtaining intrinsic performances and comparin…
An original method to compute epipoles using variable homography: application to measure emergent fibers on textile fabrics
2012
International audience; Fabric's smoothness is a key factor to determine the quality of finished textile products and has great influence on the functionality of industrial textiles and high-end textile products. With popularization of the 'zero defect' industrial concept, identifying and measuring defective material in the early stage of production is of great interest for the industry. In the current market, many systems are able to achieve automatic monitoring and control of fabric, paper, and nonwoven material during the entire production process, however online measurement of hairiness is still an open topic and highly desirable for industrial applications1. In this paper we propose a …
Architectural Scenes Reconstruction from Uncalibrated Photos and Map Based Model Knowledge
2001
In this paper we consider the problem of reconstructing architectural scenes from multiple photographs taken from arbitrarily viewpoints. The original contribution of this work is the use of a map as a source of a priori knowledge and geometric constraints in order to obtain in a fast and simple way a detailed model of a scene. We suppose images are uncalibrated and have at least one planar structure as a facade for exploiting the planar homography induced between world plane and image to calculate a first estimation of the projection matrix. Estimations are improved by using correspondences between images and map. We show how these simple constraints can be used to calibrate the cameras, t…