共查询到20条相似文献，搜索用时 31 毫秒
1.
海底影像存在着对比度低、噪声污染严重、图像质量差等问题，采用传统算子的海底管线边缘图像中含有大量的无用和断裂边缘信息。文中将多尺度边缘检测和匹配跟踪相结合，提出利用平稳小波变换的海底管线边缘检测方法；在提取边缘的同时利用匹配跟踪手段对噪声干扰进行抑制，提高图像目标边缘检测质量。通过对海底管线和测试图像边缘检测实验表明，文中所提出的方法在抑制图像噪声的干扰、提高水下目标边缘完整性方面明显优于传统的边缘提取算子，证明该算法的有效性。 相似文献
2.
This paper describes a new framework for object detection and tracking of AUV including underwater acoustic data interpolation, underwater acoustic images segmentation and underwater objects tracking. This framework is applied to the design of vision-based method for AUV based on the forward looking sonar sensor. First, the real-time data flow (underwater acoustic images) is pre-processed to form the whole underwater acoustic image, and the relevant position information of objects is extracted and determined. An improved method of double threshold segmentation is proposed to resolve the problem that the threshold cannot be adjusted adaptively in the traditional method. Second, a representation of region information is created in light of the Gaussian particle filter. The weighted integration strategy combining the area and invariant moment is proposed to perfect the weight of particles and to enhance the tracking robustness. Results obtained on the real acoustic vision platform of AUV during sea trials are displayed and discussed. They show that the proposed method can detect and track the moving objects underwater online, and it is effective and robust. 相似文献
3.
The fast update rate and good performance of new generation electronic sector scanning sonars is now allowing practicable use of temporal information for signal processing tasks such as object classification and motion estimation. Problems remain, however, as objects change appearance, merge, maneuver, move in and out of the field of view, and split due to poor segmentation. This paper presents an approach to the segmentation, two-dimensional motion estimation, and subsequent tracking of multiple objects in sequences of sector scan sonar images. Applications such as ROV obstacle avoidance, visual servoing, and underwater surveillance are relevant. Initially, static and moving objects are distinguished in the sonar image sequence using frequency-domain filtering. Optical flow calculations are then performed on moving objects with significant size to obtain magnitude and direction motion estimates. Matches of these motion estimates, and the future positions they predict, are then used as a basis for identifying corresponding objects in adjacent scans. To enhance robustness, a tracking tree is constructed storing multiple possible correspondences and cumulative confidence values obtained from successive compatibility measures. Deferred decision making is then employed to enable best estimates of object tracks to be updated as subsequent scans produce new information. The method is shown to work well, with good tracking performance when objects merge, split, and change shape. The optical flow is demonstrated to give position prediction errors of between 10 and 50 cm (1%-5% of scan range), with no violation of smoothness assumptions using sample rates between 4 and 1 frames/s 相似文献
4.
Development of real-time acoustic image recognition system using by autonomous marine vehicle 总被引：1，自引：0，他引：1
Automation of complicated underwater tasks require acoustic image based object recognition. This paper presents an acoustic image based real-time object recognition system. We proposed an acoustic image predictor to estimate an object's shape in advance. Depending on the acoustic camera's position, the predictor generates optimal template for recognition. The proposed method is implemented in our autonomous marine vehicle. For real-time processing, efficient recognition strategies are addressed. The vehicle detects an object and localizes it for recognition. In the detection process, the acoustic image's specific characteristics are used as the detection cues. In the localization process, the vehicle's horizontal and vertical positioning strategies are described. Efficient template generation method to minimize computing power is addressed. This realizes real-time recognition using the vehicle. To estimate the proposed system's accuracy and reliability, a recognition test was carried out in the field. The vehicle successfully recognized two different objects with high accuracy. 相似文献
5.
This paper presents a neural-network-based system to detect small man-made objects in sequences of sector-scan sonar images created using signals of various pulse lengths. The detection of such objects is considered out to ranges of 150 m by using an experimental sector-scan sonar system mounted on a vessel. The sonar system considered in this investigation has three modes of operation to create images over ranges of 200, 400, and 800 m from the vessel using acoustic pulses of a different duration for each mode. After an initial cleaning operation performed by compensating for the motion of the vessel, the imagery is segmented to extract objects for analysis. A set of 31 features extracted from each object is examined. These features consist of basic object size and contrast features, shape moment-based features, moment invariants, and features extracted from the second-order histogram of each object. Optimal sets of 15 features are then selected for each mode and over all modes using sequential forward selection (SFS) and sequential backward selection (SBS). These features are then used to train neural networks to detect man-made objects in each sonar mode. By the addition of a feature describing the sonar's mode of operation, a neural network is trained to detect man-made objects in any of the three sonar modes. The multimode detector is shown to perform very well when compared with detectors trained specifically for each sonar mode setting. The proposed detector is also shown to perform well when compared to a number of statistical detectors based on the same set of features. The proposed detector achieves a 92.4% probability of detection at a mean false-alarm rate of 10 per image, averaged over all sonar mode settings. 相似文献
6.
This paper describes a new framework for segmentation of sonar images, tracking of underwater objects and motion estimation. This framework is applied to the design of an obstacle avoidance and path planning system for underwater vehicles based on a multi-beam forward looking sonar sensor. The real-time data flow (acoustic images) at the input of the system is first segmented and relevant features are extracted. We also take advantage of the real-time data stream to track the obstacles in following frames to obtain their dynamic characteristics. This allows us to optimize the preprocessing phases in segmenting only the relevant part of the images. Once the static (size and shape) as well as dynamic characteristics (velocity, acceleration,…) of the obstacles have been computed, we create a representation of the vehicle's workspace based on these features. This representation uses constructive solid geometry (CSG) to create a convex set of obstacles defining the workspace. The tracking takes also into account obstacles which are no longer in the field of view of the sonar in the path planning phase. A well-proven nonlinear search (sequential quadratic programming) is then employed, where obstacles are expressed as constraints in the search space. This approach is less affected by local minima than classical methods using potential fields. The proposed system is not only capable of obstacle avoidance but also of path planning in complex environments which include fast moving obstacles. Results obtained on real sonar data are shown and discussed. Possible applications to sonar servoing and real-time motion estimation are also discussed 相似文献
7.
水声通信中的鲁棒图像编码研究 总被引：2，自引：1，他引：2
由于受各种因素的影响，水下声信道是一种传输差错率较高的信道。标准化的图像编码系统(例如JPEC；H．263，MPEG等)使用了相似的压缩技术，它们往往存在严重的错误扩散，甚至单个错误比特就可能破坏整幅图像，所以一般不适合作为水下声信道图像传输的编码方案。文章针对常用的图像编码的缺点，利用定长编码技术，提出了一种高鲁棒性的图像压缩方案。实验表明在压缩率1．25比特／象素时，压缩后的图像仍然保持了较好的质量，并且能够较好地抵抗信道误码，提高了水下声信道图像传输的质量。 相似文献
8.
In this paper, a hierarchical system, in which each level is composed by a neural-based classifier, is proposed to recognize objects in underwater images. The system has been designed to help an autonomous underwater vehicle in sea-bottom survey operations, like pipeline inspections. The input image is divided into square regions (macro-pixels) and a neural tree is used to classify each region into different object classes (pipeline, sea-bottom, or anodes). Each macro-pixel is then analyzed according to some geometric and environment constraints: macro-pixels with doubt classification are divided into four parts and re-classified. The process is iterated until the desired accuracy is reached. Experimental results, which have been performed on a large set of real underwater images acquired in different sea environments, demonstrate the robustness and the accuracy of the proposed system 相似文献
9.
V. I. Kaevitser N. A. Rimskii-Korsakov I. V. Smolyaninov V. M. Razmanov A. P. Krivtsov 《Oceanology》2016,56(5):714-720
This paper presents the results of three-dimensional acoustic seabed mapping in the region of the Taman Peninsula in the Black Sea using an interferometric side-scan sonar and an acoustic profiler. Mapping has revealed underwater objects identified as manifestations of underwater mud volcanism. Detailed analysis of sonar images of the relief and seabed profiles in the region of the objects has confirmed the original hypothesis. 相似文献
10.
Recent advances in autonomous underwater vehicle (AUV) and underwater communication technology have promoted a surge of research activity within the area of signal and information processing. A new application is proposed herein for capturing and processing underwater video onboard an untethered AUV, then transmitting it to a remote platform using acoustic telemetry. Since video communication requires a considerably larger bandwidth than that provided by an underwater acoustic channel, the data must be massively compressed prior to transmission from the AUV. Past research has shown that the low contrast and low-detailed nature of underwater imagery allows for low-bit-rate coding of the data by wavelet-based image-coding algorithms. In this work, these findings have been extended to the design of a wavelet-based hybrid video encoder which employs entropy-constrained vector quantization (ECVQ) with overlapped block-based motion compensation. The ECVQ codebooks were designed from a statistical source model which describes the distribution of high subband wavelet coefficients in both intraframe and prediction error images. Results indicate that good visual quality can be achieved for very low bit-rate coding of underwater video with our algorithm 相似文献
11.
Daniel S. Le Leannec F. Roux C. Soliman B. Maillard E.P. 《Oceanic Engineering, IEEE Journal of》1998,23(3):245-259
This paper presents a method for the matching of underwater images acquired with acoustic sensors. As a final objective, the system aims at matching data from two-dimensional scenes. The proposed approach carries out a hypothetical reasoning based on objects, represented by shadows and echoes in the sonar images, and their available features. The problem of determining measures which are invariant to changes in sonar settings and noise characteristics is addressed by mapping robust features for sonar images to a qualitative representation. To cope with the viewpoint charging appearance, the method is based on the conservation of objects' relative position from one image to another. We attempt to match geometrical structures formed by the association of three objects. The hypothetical reasoning is conducted in a decision tree framework. A tree node is generated by two objects' association, each one belonging to a respective image. Hypotheses propagation consists of creating new nodes from neighboring associations. The matching solution is determined by the selection of the decision tree's longest branch. Thus, the association mechanism is a depth-first procedure. The proposed method has been applied to real high-resolution side-scan sonar images. The matching process has shown successful and promising results which have been further improved. In particular, the parceled shadows (during the segmentation procedure) problem has been tackled 相似文献
12.
Automatic construction of high-resolution topographical maps, or determining the shape of man-made objects, targets, and obstacles for localization, identification, and/or recognition, is an important capability in the application of autonomous or intelligent underwater vehicles. In this paper, we investigate the application of underwater image models for the reconstruction of three-dimensional object shapes from the shading cues in two-dimensional optical images. We first present the results of a sensitivity analysis in support of a simplified model for a Lambertian surface illuminated by a point source in an attenuating medium, proposed in earlier work. We then generalize a closed-form solution for planar scenes, previously proposed for negligible source-camera baseline, to the case where the baseline may be increased to minimize backscatter effects. For curved surfaces, we propose two techniques based on different iterative updating strategies to recursively improve the recovered surface shape. We study the performance of various methods using synthetic data and real images acquired under different turbidity conditions 相似文献
13.
为解决多传感器水下目标纯方位跟踪中的传感器测量衰减问题,建立水下目标静态多传感器纯方位跟踪模型,将传感器测量衰减建模为统计特性已知的随机变量,基于融合中心接收到的各水声传感器的原始测量值,设计了一种集中式状态估计器结构,利用最小方差方法推导出最优的集中式目标状态估计增益。通过算例仿真可以得出,所提出的算法能够在水声传感器不做机动的前提下跟踪目标,弥补了单个水声传感器观测性不足的缺点,对比传统的集中式Kalman估计器,具有更高的精度,能够有效解决传感器测量衰减问题。 相似文献
14.
Currently, most submerged bodies use the long-baseline acoustic position system (LBL) to identify the navigation position for submerging. A precise navigation position is always the target pursued by underwater technology. The conventional long-baseline acoustic position systems normally use Kalman filter correction to handle the problem of positional errors. This article proposes a new modification, which is based on the periodically measured actual navigation distance, and associated with the three-dimensional geometrical relations between the transponder on the seabed and the navigation distance. This new modification employs the iterative approximation to modify the errors of the measured navigation position from the conventional long-baseline acoustic position system. In order to verify the availability of the modified model by the essay, the study uses the navigation position for an underwater surveying submerged body as the study object. After the numerical simulation analysis, the result shows that the modification was presented by the article can only use very few iterations to precisely modify the errors of the measured navigation position from the conventional long-baseline acoustic position system, which is highly applicable for positioning in long-term and long-distance submersion. Moreover, the modification method proposed by the paper can also help submersion positioning for the underwater vehicle, as well as the military submerged body. 相似文献
15.
Rongxin Li Haihao Li Weihong Zou Smith R.G. Curran T.A. 《Oceanic Engineering, IEEE Journal of》1997,22(2):364-375
This paper presents a photogrammetric model for digital underwater video imagery, which has been mostly applied to qualitative analysis in the marine environment. With this model, quantitative analysis of underwater images is possible, e.g., to locate positions, calculate sizes, and measure shapes of objects from image features. The underwater photogrammetric model is based on a three-dimensional optical ray tracing technique which rigorously models imaging systems with multilens configurations and multiple refractions. The calibration procedure with two independent phases has been proven to be efficient in simplifying the computation and improving the calibration accuracy. With the current imaging system configuration and photogrammetric model, an accuracy of 0.8 cm in lateral directions and 1.2 cm along the depth direction for objects located about 2-3 m from the camera system in the object space is attainable. A PC-based digital underwater photogrammetric prototype system has been developed to implement the underwater photogrammetric model 相似文献
16.
17.
18.
水下拖体声学超短基线定位测量及其卡尔曼滤波技术 总被引：4，自引：2，他引：4
水声超短基线定位技术是探测水下目标的有效手段。超短基线定位测得的原始数据具有不同程度的随机离散性。为了得到能够真实反映目标运动轨迹变化的坐标数据 ,本文应用了卡尔曼滤波技术来处理定位原始数据 ,取得了良好的结果 相似文献
19.
《Oceanic Engineering, IEEE Journal of》2005,30(3):570-587
Underwater imaging is important for scientific research and technology as well as for popular activities, yet it is plagued by poor visibility conditions. In this paper, we present a computer vision approach that removes degradation effects in underwater vision. We analyze the physical effects of visibility degradation. It is shown that the main degradation effects can be associated with partial polarization of light. Then, an algorithm is presented, which inverts the image formation process for recovering good visibility in images of scenes. The algorithm is based on a couple of images taken through a polarizer at different orientations. As a by-product, a distance map of the scene is also derived. In addition, this paper analyzes the noise sensitivity of the recovery. We successfully demonstrated our approach in experiments conducted in the sea. Great improvements of scene contrast and color correction were obtained, nearly doubling the underwater visibility range. 相似文献
20.
Because of the difficulties in accurately characterizing the statistical behavior of underwater acoustic channels, tolerance to uncertain statistical modeling is an important property for underwater acoustic signal processing procedures to possess. This paper provides an overview of a number of techniques developed in recent years that can be applied to provide uncertainty tolerance in underwater signal processing applications. In addition to a discussion of general concepts of uncertainty tolerance, specific methods for attaining tolerance to uncertainty in temporal/spatial statistics for procedures such as Wiener and matched filtering, time-delay estimation, sonar system design, and signal prediction are reviewed. Tolerance to uncertainty in amplitude statistics is also a key issue in underwater channels, and techniques for achieving this goal are discussed in the contexts of signal estimation, identification, and detection procedures. 相似文献