214 research outputs found
A Novel Approach for Ellipsoidal Outer-Approximation of the Intersection Region of Ellipses in the Plane
In this paper, a novel technique for tight outer-approximation of the
intersection region of a finite number of ellipses in 2-dimensional (2D) space
is proposed. First, the vertices of a tight polygon that contains the convex
intersection of the ellipses are found in an efficient manner. To do so, the
intersection points of the ellipses that fall on the boundary of the
intersection region are determined, and a set of points is generated on the
elliptic arcs connecting every two neighbouring intersection points. By finding
the tangent lines to the ellipses at the extended set of points, a set of
half-planes is obtained, whose intersection forms a polygon. To find the
polygon more efficiently, the points are given an order and the intersection of
the half-planes corresponding to every two neighbouring points is calculated.
If the polygon is convex and bounded, these calculated points together with the
initially obtained intersection points will form its vertices. If the polygon
is non-convex or unbounded, we can detect this situation and then generate
additional discrete points only on the elliptical arc segment causing the
issue, and restart the algorithm to obtain a bounded and convex polygon.
Finally, the smallest area ellipse that contains the vertices of the polygon is
obtained by solving a convex optimization problem. Through numerical
experiments, it is illustrated that the proposed technique returns a tighter
outer-approximation of the intersection of multiple ellipses, compared to
conventional techniques, with only slightly higher computational cost
Rotation-invariant features for multi-oriented text detection in natural images.
Texts in natural scenes carry rich semantic information, which can be used to assist a wide range of applications, such as object recognition, image/video retrieval, mapping/navigation, and human computer interaction. However, most existing systems are designed to detect and recognize horizontal (or near-horizontal) texts. Due to the increasing popularity of mobile-computing devices and applications, detecting texts of varying orientations from natural images under less controlled conditions has become an important but challenging task. In this paper, we propose a new algorithm to detect texts of varying orientations. Our algorithm is based on a two-level classification scheme and two sets of features specially designed for capturing the intrinsic characteristics of texts. To better evaluate the proposed method and compare it with the competing algorithms, we generate a comprehensive dataset with various types of texts in diverse real-world scenes. We also propose a new evaluation protocol, which is more suitable for benchmarking algorithms for detecting texts in varying orientations. Experiments on benchmark datasets demonstrate that our system compares favorably with the state-of-the-art algorithms when handling horizontal texts and achieves significantly enhanced performance on variant texts in complex natural scenes
Data Extraction as Input for the Energy analysis of an urban district with UMI.
The energy usage of an urban district has become a major subject of study and interest since we observed a significant expansion of cities caused by the movement of inhabitants. Sustainability of urban areas is mainly related to interactions between street patterns and building distances. Monitoring these connections in terms of energy flows creates possibilities of optimizing building construction and retrofitting. There are many tools used to make this possible.In this paper, we want to demonstrate how it is possible to import the 3D structure of an urban area recorded in an SHP file into the Urban Modeling Interface software. The data extraction protocol we developed to this aim principally consists in approximating clusters of XYZ coordinates into a set of boxes with minimum loss in geometry, orientation, and position of buildings. Estimations of energy consumption and CO2 are among the outcomes we were able to obtain from imported data into UMI. Using the developed data extraction strategy, we can potentially analyze the energy usage of an entire city
Learning and Recognizing Archeological Features from LiDAR Data
We present a remote sensing pipeline that processes LiDAR (Light Detection
And Ranging) data through machine & deep learning for the application of
archeological feature detection on big geo-spatial data platforms such as e.g.
IBM PAIRS Geoscope.
Today, archeologists get overwhelmed by the task of visually surveying huge
amounts of (raw) LiDAR data in order to identify areas of interest for
inspection on the ground. We showcase a software system pipeline that results
in significant savings in terms of expert productivity while missing only a
small fraction of the artifacts.
Our work employs artificial neural networks in conjunction with an efficient
spatial segmentation procedure based on domain knowledge. Data processing is
constraint by a limited amount of training labels and noisy LiDAR signals due
to vegetation cover and decay of ancient structures. We aim at identifying
geo-spatial areas with archeological artifacts in a supervised fashion allowing
the domain expert to flexibly tune parameters based on her needs
A modification of Graham’s algorithm for determining the convex hull of a finite planar set
In this paper, in our modification of Graham scan for determining the
convex hull of a finite planar set, we show a restricted area of the examination
of points and its advantage. The actual run times of our scan and Graham
scan on the set of random points shows that our modified algorithm runs
significantly faster than Graham’s one
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