Digitizations Preserving Topological and Differential Geometric Properties

In this paper, we present conditions which guarantee that every digitization process preserves important topological and differential geometric properties. These conditions also allow us to determine the correct digitization resolution for a given class of real objects. Knowing that these properties are invariant under digitization, we can then use them in feature-based recognition. Moreover, these conditions imply that only a few digital patterns can occur as neighborhoods of boundary points in the digitization. This is very useful for noise detection, since if the neighborhood of a boundary point does not match one of these patterns, it must be due to noise. Our definition of a digitization approximates many real digitization processes. The digitization process is modeled as a mapping from continuous sets representing real objects to discrete sets represented as digital images. We show that an object A and the digitization of A are homotopy equivalent. This, for example, implies that the digitization of A preserves connectivity of the object and its complement. Moreover, we show that the digitization of A will not change the qualitative differential geometric properties of the boundary of A ; i.e., a boundary point which is locally convex cannot be digitized to a locally concave pixel and a boundary point which is locally concave cannot be digitized to a locally convex pixel.     

沿海地区不同空间尺度的典型地物相干性研究

基于雷达干涉相干原理,利用6景时间跨度为4年的ENVISAT ASAR雷达影像,分析了不同空间尺度（分辨率分别为20 m和80 m）的苏中沿海地区典型地物的相干特征。研究结果表明：①低分辨率图像的地物相干性总体上要低于高分辨率图像,但前者的相干系数对比度要优于后者;②对于面积较小的地物,空间尺度的变化对相干性的影响显著,而对于面积较大的地物,则影响较小。该研究成果可用于提高土地利用类型分类的精度以及有效地提取长时间地表形变反演中所需的高相干点信息。     

两级上下文卷积网络宽视场图像小目标检测方法

目标检测和识别已经在输电线路巡检中被广泛采用。由于图像数据量大,小目标分辨率低,现有的图像金字塔、特征金字塔和多异构特征融合等方法虽能准确地检测目标,却非常耗时,因而快速、准确地检测宽视场图像中小目标仍是一个挑战。此算法提出一个两个Faster-RCNs级联的上下文宽视场小目标检测卷积网络,首先,针对降分辨率的宽视场图像,利用一个Faster R-CNN来检测目标的上下文区域,然后,针对上下文区域对应的高分辨率原始图像,利用Faster R-CNN来检测来小目标。我们用航拍输电线路图像数据集进行了目标检测试验,试验结果表明,小目标检测方法达到了88%的检测精度,比单级Faster R-CNN检测方法具有更高的准确率。     

A modular neural network for super-resolution of human faces

This paper presents the original and versatile architecture of a modular neural network and its application to super-resolution. Each module is a small multilayer perceptron, trained with the Levenberg-Marquardt method, and is used as a generic building block. By connecting the modules together to establish a composition of their individual mappings, we elaborate a lattice of modules that implements full connectivity between the pixels of the low-resolution input image and those of the higher-resolution output image. After the network is trained with patterns made up of low and high-resolution images of objects or scenes of the same kind, it will be able to enhance dramatically the resolution of a similar object’s representation. The modular nature of the architecture allows the training phase to be readily parallelized on a network of PCs. Finally, it is shown that the network performs global-scale reconstruction of human faces from very low resolution input images.     

基于动态超分辨率的输电线路部件检测方法

在无人机输电线路巡检过程中,由于部分输电线路部件较小,而且无人机搭载的相机像素有一定限制,同时必须与输电线路保持一定的安全距离,导致拍摄的图像的分辨率较低、目标较小.针对这一问题,提出了一种基于动态超分辨率的输电线路部件检测方法,将超分网络引入到输电线路巡检过程中.实验结果表明,该方法对输电线路低分辨率输入图像和小目标...     

Efficiency of characterizing ellipses and ellipsoids by discretemoments

In this paper, our studies are focused on ellipses and problems related to their representation and reconstruction from the data resulting from their digitization. The main result of the paper is that a finite number of discrete moments, corresponded to digital ellipses, is in one-to-one correspondence with digital ellipses, which enables coding of digital ellipses with an asymptotically optimal amount of memory. In addition, the problem of reconstruction, based on the same parameters, is considered. Since the digitization of real shapes causes an inherent loss of information about the original objects, the precision of the original shape estimation from the corresponding digital data is limited. We derive a sharp upper bound for the errors in reconstruction of the center position and half-axes of the ellipse, in function of the applied picture resolution (i.e., the number of pixels per unit). An extension of these results to the 3D case is also given     

Analysis of large format camera photographs of the Po Delta,Italy, for topographic and thematic mapping

Abstract

Photographs produced by two generations of photogrammetric cameras, the first generation metric camera and the second generation large format camera, are compared with regard to their interpretability for topographic and thematic mapping. The latter part of this paper deals with interpretation problems which depend mainly on the characteristics of the black and white film. It can be shown that digitization and digital image enhancement techniques improve the interpretability to a certain extent. The conclusions, when looking forward to a second flightof the metric camera, are that the installation of forward motion compensation in combination with high resolution films will be a step forward in the development of a European photogrammetric camera.     

Improvement of the precision of the gradient method and object tracking using optical flow

In this study, the spatial local optimization method was improved to obtain high precision of optical flow for cases in which the object movement changes substantially and a method to trace the loci of moving objects was considered. In the spatial local optimization method, the precision of the optical flow when the object movement changes substantially becomes a problem. Therefore, to make the object movement relatively small, we obtained flow vectors from the image sequence to drop the resolution of the original input image sequence to half the initial resolution. flow vectors were then obtained from the original input image sequence that were smaller than the threshold value. We show that the precision of the optical flow when the object movement changes substantially is improved by this method. Method used to trace the loci of moving objects was demonstrated. We obtained clusters from histograms of flow vectors and pursued each cluster. We show that it is possible to trace moving objects by this method. This work was presented, in part, at the 7th International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002     

Petroglyph digitization: enabling cultural heritage scholarship

The digitization of antiquities is facilitating a renaissance for scholars who have unprecedented access to rich representations of objects. Cultural Heritage digitization is a central challenge, and its subtleties are intertwined with object properties and the constraints of physical access and handling. In this paper, we present the design and analysis of a system built for the digitization of Puerto Rican petroglyphic iconography. The petroglyphs exhibit unique properties (shape, size, surface) that determine system design choices. The 3D models obtained with the system support new scholarly and educational activities, including interactive surface lighting, feature highlighting and annotation through mark-up, and immersive viewing using large-scale displays.     

Micromanipulation system using scanning electron microscope

In this study, we aimed to develop a micromechanism in which constituent parts of μm order are used and to establish the handling technology required to achieve this. On the basis of the results of previous studies, we fabricated end effectors driven by a small piece of shape memory alloy (SMA) and succeeded in grasping microobjects on the order of 10–40 μm. However, when the size of an object is 10 μm or smaller, because this size is equivalent to the resolution of optical microscopes, it is necessary to improve and change the design of observation technology to manipulate much smaller objects. In this study, an SEM was used as the observation system and the manipulation system was modified to be compatible with this observation system. A manipulation system for grasping much smaller objects was designed and developed.     

View-dependent textured splatting

We present a novel approach to render low resolution point clouds with multiple high resolution textures – the type of data typical from passive vision systems. The low precision, noisy, and sometimes incomplete nature of such data sets is not suitable for existing point-based rendering techniques that are designed to work with high precision and high density point clouds. Our new algorithm – view-dependent textured splatting (VDTS) – combines traditional splatting with a view-dependent texturing strategy to reduce rendering artifacts caused by imprecision or noise in the input data.VDTS requires no pre-processing of input data, addresses texture aliasing, and most importantly, processes texture visibility on-the-fly. The combination of these characteristics makes VDTS well-suited for interactive rendering of dynamic scenes. Towards this end, we present a real-time view acquisition and rendering system to demonstrate the effectiveness of VDTS. In addition, we show that VDTS can produce high quality rendering when the texture images are augmented with per-pixel depth. In this scenario, VDTS is a reasonable alternative for interactive rendering of large CG models.     

地表粗糙度的测量计算方法及其对微波辐射散射的影响分析

地表粗糙度反映了地表的微小起伏,是土壤水分微波遥感反演研究中重要的地表参数.以闪电河流域为研究区,首先利用针板法对不同地物下的地表粗糙度进行测量,然后对测量数据进行透视变换、数字化、倾斜校正及周期校正等一系列的处理,计算得到不同地表的粗糙度结果.研究表明:在使用针板法测量地表粗糙度时,为校正不同剖面测量姿态的影响需要进...     

一种高分辨率遥感图像分割算法

文章研究总结了一种适合于高分辨率可见光遥感图像分割的算法。该算法是一种结合数学形态学区域分割算法和Canny边缘检测算法的综合图像分割算法,可以有效地将图像中的多个小目标分割出来。     

Systems and algorithms for autonomous and scalable crowd surveillance using robotic PTZ cameras assisted by a wide-angle camera

We report an autonomous surveillance system with multiple pan-tilt-zoom (PTZ) cameras assisted by a fixed wide-angle camera. The wide-angle camera provides large but low resolution coverage and detects and tracks all moving objects in the scene. Based on the output of the wide-angle camera, the system generates spatiotemporal observation requests for each moving object, which are candidates for close-up views using PTZ cameras. Due to the fact that there are usually much more objects than the number of PTZ cameras, the system first assigns a subset of the requests/objects to each PTZ camera. The PTZ cameras then select the parameter settings that best satisfy the assigned competing requests to provide high resolution views of the moving objects. We propose an approximation algorithm to solve the request assignment and the camera parameter selection problems in real time. The effectiveness of the proposed system is validated in both simulation and physical experiment. In comparison with an existing work using simulation, it shows that in heavy traffic scenarios, our algorithm increases the number of observed objects by over 210%.     

Dynamic Tubular Grid: An Efficient Data Structure and Algorithms for High Resolution Level Sets

Level set methods [Osher and Sethian. Fronts propagating with curvature-dependent speed: algorithms based on Hamilton–Jacobi formulations. J. Comput. Phys. 79 (1988) 12] have proved very successful for interface tracking in many different areas of computational science. However, current level set methods are limited by a poor balance between computational efficiency and storage requirements. Tree-based methods have relatively slow access times, whereas narrow band schemes lead to very large memory footprints for high resolution interfaces. In this paper we present a level set scheme for which both computational complexity and storage requirements scale with the size of the interface. Our novel level set data structure and algorithms are fast, cache efficient and allow for a very low memory footprint when representing high resolution level sets. We use a time-dependent and interface adapting grid dubbed the “Dynamic Tubular Grid” or DT-Grid. Additionally, it has been optimized for advanced finite difference schemes currently employed in accurate level set computations. As a key feature of the DT-Grid, the associated interface propagations are not limited to any computational box and can expand freely. We present several numerical evaluations, including a level set simulation on a grid with an effective resolution of 1024³     

Automated Displacement for Large Numbers of Discrete Map Objects

Effective displacement is achieved by sharing small movements among a group of objects in order to minimize loss of positional accuracy and maintain the gestalt and topology of the map objects. This research was driven by a desire to implement a simple but effective way of handling large numbers of map objects that may require displacement. The algorithm works by considering, for each object in turn, a number of alternate positions close to its current location. The location which minimizes overlap among the neighbouring objects is chosen. As the program iterates, the objects effectively migrate small distances within the map space in search of solutions. The idea is relatively simple but produces visually acceptable solutions to the displacement of large numbers of objects with very low processing overhead. This paper describes the algorithm in detail, illustrates its application, refinement and evaluation. Received December 11, 1998; revised October 14, 1999.     

Region digitization and boundary estimation

Digital complexes most often arise in practice as binary images, digitized by computer vision systems from real objects. In this paper, schemes for region digitization and boundary estimation are discussed in relation to the actual physical process of binary image acquisition. The region digitization scheme motivated naturally by such a discussion is also appropriate for use in theoretical studies of digital complexes. The same discussion suggests a method for obtaining an estimate of the boundary of an object from its binary image.     

Detecting textured objects using convex hull

In this paper, we present a methodology of locating 3D objects of known shapes from a single gray-scale image, in particular objects with rich textures on the surface. While traditional approaches identify objects by grouping and matching local features, we locate the object in the image using its convex hull, a high level feature not given much attention in the image using literature. A “direct line detection” algorithm is developed to detect line segments directly from the gray-scale image divided in small blocks. Lines are clustered and convex hull of a single or group of clusters is computed and edited to extract the 2D contour of the object. Successful experiments on rectangular boxes and cylinders show the effectiveness of the convex hull approach and its potential usage in industrial applications. Part of the work discussed in this paper was performed when both authors were affiliated with Symbol Technologies.     

PATSCAN—a microprocessor-based pattern scanner system

PATSCAN, a low-cost pattern scanner for digitization of optical patterns is described. The scanner system has been developed using Reticon solid-state integrated two-dimensional image sensors. The various control signals have been generated using hardware also under program control. The scanner yields sufficiently high resolution, low noise digitized patterns which could be subsequently classified.     

一种基于深度学习的遥感图像目标检测算法

遥感图像分析在国土资源管理、海洋监测等领域有着极为广阔的应用前景。深度学习技术已在图像处理领域取得突破性进展,然而,遥感图像固有的尺寸大、目标小而密集等特点,使得将面向普通图像的深度学习方法用于遥感目标检测普遍存在定位不准确、小目标检测难、大图检测精度差等问题。针对上述难题, 提出了一种新型遥感图像目标检测算法DFS。与传统机器学习方法相比,DFS 设计了新的维度聚类模块、定制损失函数和滑动窗口分割检测机制。其中,维度聚类模块通过设计聚类机制优化定制先验框,提高定位精度;定制损失函数提高对船只等小目标的检测精度;滑动窗口分割检测解决大图检测精度低的问题。在经典遥感数据集上开展的实验对比表明,与YOLOv2相比,DFS算法的mAP提高了256%,小目标检测效率及大图检测效能大幅提高。