Showing papers on "Change detection published in 1993"

Detection of abrupt changes: theory and application

Abstract: This book is downloadable from http://www.irisa.fr/sisthem/kniga/. Many monitoring problems can be stated as the problem of detecting a change in the parameters of a static or dynamic stochastic system. The main goal of this book is to describe a unified framework for the design and the performance analysis of the algorithms for solving these change detection problems. Also the book contains the key mathematical background necessary for this purpose. Finally links with the analytical redundancy approach to fault detection in linear systems are established. We call abrupt change any change in the parameters of the system that occurs either instantaneously or at least very fast with respect to the sampling period of the measurements. Abrupt changes by no means refer to changes with large magnitude; on the contrary, in most applications the main problem is to detect small changes. Moreover, in some applications, the early warning of small - and not necessarily fast - changes is of crucial interest in order to avoid the economic or even catastrophic consequences that can result from an accumulation of such small changes. For example, small faults arising in the sensors of a navigation system can result, through the underlying integration, in serious errors in the estimated position of the plane. Another example is the early warning of small deviations from the normal operating conditions of an industrial process. The early detection of slight changes in the state of the process allows to plan in a more adequate manner the periods during which the process should be inspected and possibly repaired, and thus to reduce the exploitation costs.

Nonparametric methods in change-point problems

Abstract: Preface. Introduction: Goals and problems of change point detection. 1. Preliminary considerations. 2. State-of-the-art review. 3. A posteriori change point problems. 4. Sequential change point detection problems. 5. Disorder detection of random fields. 6. Applications of nonparametric change point detection methods. 7. Proofs, new results and technical details. References.

Change detection techniques for ERS-1 SAR data

Abstract: Several techniques for detecting temporal changes in satellite synthetic-aperture radar (SAR) imagery are compared, using both theoretical predictions and spaceborne SAR data collected by the first European Remote Sensing Satellite, ERS-1. In a first set of techniques, changes are detected based on differences in the magnitude of the signal intensity between two dates. Ratioing of the multidate radar intensities is shown to be better adapted to the statistical characteristics of SAR data than subtracting, and works best when the number of looks is large. In a second set of techniques, changes are detected based on estimates of the temporal decorrelation of speckle. This method works best with one-look complex amplitude data, but can also be used with intensity data provided that the number of looks is small. The two techniques are compared using actual SAR data collected by ERS-1. The results illustrate the viability as well as the complementary character of these techniques for detecting changes in the structural and dielectric properties of remotely sensed surfaces. >

Change detection techniques for ERS-1 SAR data

Abstract: Several techniques for detecting temporal changes in satellite synthetic-aperture radar (SAR) imagery are compared, using both theoretical predictions and spaceborne SAR data collected by the first European Remote Sensing Satellite, ERS-1. In a first set of techniques, changes are detected based on differences in the magnitude of the signal intensity between two dates. Ratioing of the multidate radar intensities is shown to be better adapted to the statistical characteristics of SAR data than subtracting, and works best when the number of looks is large. In a second set of techniques, changes are detected based on estimates of the temporal decorrelation of speckle. This method works best with one-look complex amplitude data, but can also be used with intensity data provided that the number of looks is small. The two techniques are compared using actual SAR data collected by ERS-1. The results illustrate the viability as well as the complementary character of these techniques for detecting changes in the structural and dielectric properties of remotely sensed surfaces. >

Remote sensing techniques in the analysis of change detection

Abstract: A review of remote sensing techniques in change detection studies is presented. Due to the nature of imagery examined, most change detection studies have involved the use of Advanced Very High Resolution Radiometer (AVHRR), Landsat Thematic Mapper (TM) and Multispectral Scanner (MSS), SPOT data, and aerial photography. Change detection techniques have included transparency compositing, image differencing, classification, band ratioing, and principal components analysis. This paper will focus on a review of the utility of these methods for various resource applications.

A knowledge-based vision system for detecting land changes at urban fringes

Abstract: An experimental vision system for remote sensing land use/cover change detection is presented. The system was designed to monitor the processes of urban development. The design strategy, system structure, and image analysis sequence are addressed. Some experimental results are presented. Techniques are described in detail which were aimed at addressing the key aspects to constructing a knowledge-based vision system: preprocessing, spatial representation and manipulation, and incorporating ancillary data. >

Change Detection and Input Design in Dynamical Systems

Abstract: From the Publisher: Provides information on the detection and diagnosis of abrupt changes in the dynamics of single input single output stochastic systems and the design of auxiliary inputs for this purpose. The problem is put in a decision theoretic framework and the concepts of classicial decision theory are augmented to accommodate the input design as well as the decision rules for change detection. The sequential probability ratio test (SPRT) is investigated in detail. The detection mechanism as well as the input design techniques are extended to the multihypothesis case.

Picture data coding method, picture data coder using the method, picture data decoding method, picture data decoder using the method, scene change detection method, scene change detection method, scene change detector, scene change recorder, and picture data scene change recording and reproducing device

Abstract: PURPOSE:To code/decode a moving picture by automatically extracting a scene change of the moving picture with respect to a coder of the moving picture or the like. CONSTITUTION:Moving picture data are inputted from a terminal 110a. A coding section 111 codes moving picture data in the unit of frames, A code buffer 112 stores a code quantity per one frame obtained from the coding. A detection condition setting section 114 sets a detection condition (reference value of differential coding quantity) designated by detection designation data inputted from a terminal 110b. A scene discrimination section 113 calculates a difference between a code quantity of a current frame inputted from the code buffer 112 and a code quantity of a preceding frame and activates a COS code and a select signal representing a scene change when the difference is the detection condition (reference value of differential coding quantity) or over. A switch 115 receives the select signal in which code data representing a frame of a scene change are added to the code data of the current current frame and the result is outputted externally via an output terminal 110c.

Motion detection robust to perturbations: A statistical regularization and temporal integration framework

Abstract: The authors present a scheme for motion detection exploiting temporal integration and local contextual information. A multiscale temporal decomposition is supplied to the original sequence. Change detection is performed using a likelihood test at each temporal scale. The decision process is formalized within a statistical regularization framework and takes advantage of a tracking module. Motion detection is achieved by minimizing an energy function. This function involves three terms, expressing (1) adequacy between temporal variations at different scales and motion labels, (2) local spatial regularization, and (3) coherence between temporal prediction of change area locations and motion labels. Experimental results on real scenes are reported. >

Change detection on longitudinal data in periodontal research

Abstract: Longitudinal data of attachment level (AL) or the alveolar bone level are often used to assess the progression of periodontal disease. This paper tries to identify the most efficient method to detect the changes of AL in a general periodontal research environment; that is, a sequential decision based on multiple sites. Several existing methods suggested in the periodontal research literature such as the tolerance, running median, cusum, and regression methods as well as change-point detection methods in the statistical literature are examined. It is found that the regression method is most convenient among the several methods that are equally effective in change detection. Formulae, tables and their usage are discussed in detail.

Video index display device

Abstract: PURPOSE: To easily retrieve a required scene by collecting plural index pictures obtained from video image comprising plural consecutive scenes for each scene and displaying the collected picture onto an edit pattern. CONSTITUTION: A scene change detection section 2 detects a scene from a digital moving picture. When a scene change is detected by the detection section 2, information such as a detected frame picture and a scene number is managed by a scene change management section 3. On the other hand, a characteristic frame detection section 4 matches a shape pattern stored in a material management section 5 as to a digital moving picture to detect a characteristic frame in an index picture. Then the scene change management section 3 manages the index detected by the scene change detection section 2 and the characteristic frame detection section 4 for each scene and outputs the index information to an index display section 6 and it is displayed on an edit pattern and recorded on a recording section 9. COPYRIGHT: (C)1994,JPO&Japio

Stereo echo canceller

Abstract: PURPOSE: To obtain the stereo echo canceller in which increase in echo generated between a microphone and a speaker is quickly suppressed. CONSTITUTION: A talker change detection means 17 is connected between input terminals 1 and 2 and receives reception signals x1j, x2j and detects a change in talkers at a remote point based on a change in the signal level. First and second short time power average calculation means 18, 19 are connected respectively to the input terminals 1, 2 and a quantity comparator means 110 using the result to discriminate the relation of the quantity. A 1st adaptive control means 111 sets an update gain of a 1st adaptive filter 11 to zero for a prescribed period when the talker change detection means 17 detects a change in talkers at remote points and it is discriminated that a short time power mean value of the 1st reception signal is larger and sets an update gain of a 2nd adaptive filter 12 to zero for a prescribed period when the talker change detection means 17 detects a change in talkers at remote points and it is discriminated that a short time power mean value of the 2nd reception signal is larger to stop the adaptive processing. COPYRIGHT: (C)1995,JPO

The ordering of multi temporal fuzzy land-cover information derived from Landsat MSS data

Abstract: Change detection from satellite imagery is fraught with problems of precision, and detection of incorrect changes at rates of up to 80% of pixels are not uncommon in the literature. In this paper, the Fuzzy c‐Means classifier, which yields fuzzy membership values for each pixel in all land cover types, is applied to imagery of the same area at different dates where no actual change is know to have occurred. Analysis of this ordered data and the associated cover types shows that the rate of change, initially identified as 40.76% of pixels in hard classifications, which is clearly erroneous, can be reduced to about 0.32%; a rate that is considered to be very acceptable for most applications.

Multitemporal texture analysis of features computed from remotely sensed imagery

Abstract: A concept is presented for analyzing the texture of changes in multi-temporal imagery. In more traditional change detection approaches, spectral signatures or textures from two or more spatially-coincident image sets are compared. Spatial cooccurrence has been used by various researchers to compute texture measures. These measures, representing the two dimensional x/y spatial variability in an image, are compared against two dimensional textures in other images. This paper introduces the concept of computing image texture using spatial cooccurrence matrices by searching, not just in the x/y space, but in the third dimension of time, or t space. An example problem is described in which changes in forest canopies are evaluated. A spectral mixture model for computing forest canopy closure from Landsat TM data is described. The canopy closure feature images from two spatially coincident, but time varying image sets are evaluated using three dimensional texture analysis. The technique lends itself to evaluation of systematic or localized forest changes; e.g. uniform thinning vs. localized damage.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A knowledge-based approach to the detection and interpretation of changes in aerial images

Abstract: Traditional approaches to change detection do not give information about the cause of changes and, therefore, do not help to automatically evaluate their significance and relevance with respect to a given analysis task. In this contribution the authors present a knowledge-based approach to the problem of interpreting changes which allows one to compare information on a symbolic image description level rather than on a pure data level. The authors introduce a system architecture and discuss the structure and function of its main three components. >

Robust fault detection in a welding process using parametric estimation

Abstract: This paper deals with the application of adaptive parameter estimation and change detection tools for the detection of faults in the welding of steel sheets. Considering the non-stationary primary current signal, two kinds of fault have to be detected: abrupt changes and changes in the degree of non-stationarity. For this last problem, a method which uses a minimax approach is proposed. >

Applications of Nonparametric Change-Point Detection Methods

Abstract: The nonparametric methods of change-point detection developed in this book have been tested many times by statistical simulation. However, the most interesting point, in our opinion, is running the methods on real statistical data. We had the opportunity to verify our results on three practical problems: (1) Computer analysis of historical texts; (2) Computer-aided space data processing: the analysis of information obtained from an orbiting satellite; (3) Computer analysis of geophysical information.

Optimal sequential deduction and isolation of changes in stochastic systems

Abstract: The purpose of this paper is to give a new statistical approach to the change diagnosis (detection/isolation) problem. The change detection problem has received extensive research attention. On the contrary, change isolation is mainly an unsolved problem. We consider a stochastic dynamical system with aburpt changes and investigate the multihypothesis extension of Lorden's results. We introduce a joint criterion of optimality for the detection/isolation problem and then design a change detection/isolation algorithm. We also investigate the statistical properties of this algorithm. We prove a lower bound for the criterion in a class of sequential change detection/isolation algorithms. It is shown that the proposed algorithm is asymptotically optimal in this class. The theoretical results are applied to the case of additive changes in linear stochastic models.

Texture segmentation by change detection in second and higher order statistics

Abstract: In this study we consider unsupervised texture segmentation via non-parametric change detection of locally estimated image features. The change detection approach is straightforward and may be used with first, second, or higher order statistics. Adaptive smoothing is used to reduce the variance in local statistic estimates while preserving step behavior due to the presence of a region boundary. The approach is combined with Laws (1980) energy operators by detecting a change in the variance of the image resulting from application of a Laws mask to the original texture image. >

Vision based safety device for uncontrolled robotic environments

Abstract: A comparative study of fast motion detectors for image sequences in a real world scene is presented. We discuss particularly the problem of sensitivity towards the changes of illumination which induce false detections. Algorithms are tested with two sequences of grey value images, one containing a real object motion, and a second one which contains changes due to the variation of illumination. A new algorithm of change detection using colour information is introduced. The experimentation showed that this algorithm permits to take into account the illumination component and also reacts satisfactory towards security constraints. >

State change detection control circuit

Abstract: PURPOSE:To suppress interruption to a CPU in the case of generating a lot of state changes at the state change detection circuit to detect the states of binary contact inputs and to execute an interrupted report to the CPU. CONSTITUTION:This circuit is provided with a state change detection circuit 11 to detect the ON/OFF state change of the contact input, interruption generating circuit 12, state change generating ratio judging circuit 13 to investigate a state change ratio by monitoring the contact input, input signal sampling circuit 15 to extend sampling time according to the instruction of the state change generating ratio judging circuit 13 in the case of generating a lot of state changes and to change the sampling time so as to suppress the interruption to a CPU 2, and maximum state change generating ratio storage circuit 14 to store the upper limit of the maximum state change generating ratio. Then, the sampling time of the input signal is made variable corresponding to the generation of the state change, and the generation of the interruption to the CPU 2 is controlled.

Multisensor Change Detection for Surveillance Applications

Abstract: The problem of detecting man-made objects in a natural environment based on analysis of image sequences is discussed. Both real-time and short term change detection are required to operate at low false alarm rates in a cluttered environment. A surveillance system testbed is described which detects significant changes in images from visible and thermal sensors. The system is initialized with an operator-guided segmentation to partition the scene into regions of similar noise characteristics and processing priorities. Images from the two sensors are registered and a common segmentation is used for both. Region based adaptive change detection is employed for operation under changing thermal and illumination conditions. Detection processing in corresponding regions of the two sensors’ images are closely coupled. A detection in one region triggers additional processing in the same region from the other sensor. Results from several operating environments are given to illustrate its capabilities and directions for further development of the system.

Transmission line clock extracting system

Abstract: PURPOSE:To prevent the circuit for the system from malfunction due to noise superimposed on reception data in the system in which an oscillator is utilized to extract a clock. CONSTITUTION:A change point detection circuit 2 detects a leading of reception data 1 and outputs change point information 5 to a change point detection protection circuit 3 and a change point prediction circuit 4. The change point detection protection circuit 3 decides whether or not a given change point is adequate by change point information 5 based on a prediction output 6 of the change point prediction circuit 4 and outputs a control signal 8 to a frequency divider circuit 7 and the change point prediction circuit 4. The change point prediction circuit 4 predicts a change point appearing next based on a frequency division output 9 of the frequency divider circuit 7, the change point information 5 and the control signal 8 of the change point detection protection circuit 3 and outputs a prediction output 6 to the change point detection protection circuit 3. The frequency divider circuit 7 frequency-divides the output signal of an oscillator 10 based on the control signal 8 to output a transmission line extract clock 11 having an object frequency.

Systems Concepts for Visual Texture Change Detection Strategy

Abstract: The goals of this paper is to develop effective algorithms to achieve acceptable performance in what we call Visually Detectable Defects (V.D.D); and also to define from systems concepts a test strategy. The main problem in V.D.D. has been finally identified as that of the detection and labelling of subtle changes in the texture of an image. In consequence, none of the standard procedures for texture discrimination gave good results, so that increasing the complexity of the process was decided upon, to provide a new decision level.