共查询到18条相似文献,搜索用时 125 毫秒
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由于受卫星平台的运动、传感器成像特性、卫星的星历与姿态和地形起伏等客观因素的影响,任何使用线阵列 CCD 传感器的航天遥感系统在成像过程中都会产生影像变形。 因此在卫星设计过程中,必须综合考虑这些因素对成像结果的影响。 针对这一问题,从线阵高分辨率遥感卫星成像方式及敏捷型卫星的成像特点出发,综合考虑成像时各种几何变形因素的影响,并依据严格成像模型,对所设计的传感器进行成像模拟,最后对模拟影像进行变形分析,以检核遥感卫星的系统设计是否能满足用户要求。 相似文献
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我国“海洋1”号卫星(HY-1)CCD图像数据定量化条带消除研究 总被引:5,自引:0,他引:5
条带(striping)对于大量的航天和航空传感器来说是一种普遍存在的现象,任何使用多个探测器进行数据获取的遥感器图像数据中均存在条带.目前消除条带的算法主要是针对光机扫描仪,对于CCD相机工作做得比较少.针对HY-1CCD线阵推扫式多光谱相机的特点,以及发射前辐射定标的结果,对遥感器图像数据中的条带问题进行了预研,提出了一种定量化的消条带算法.该方法根据卫星数据特性求出各探测器间的均衡化曲线以反映探测器之间的差异,并据此来消除条带.实验结果表明该方法能够有效解决CCD相机的条带问题,而且可以保持数据原有的物理意义,并可与在轨辐射校正衔接,保证发射前后定标算法的一致性. 相似文献
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海洋一号C卫星(HY-1C)搭载的海岸带成像仪(coastal zone imager,CZI)为满足大幅宽成像需求,采用双相机组合成像,每台相间使用2片4色电荷耦合光敏元器件(charge-coupled device,CCD)拼接。从严密几何成像模型出发,对相机成像过程中存在的系统误差进行分析,采用一种基于探元指向角的几何定标模型,并结合CZI相机设计特点与几何特性,设计出一套针对HY-1C/CZI的几何定标方案。首先利用CZI参考基准波段影像与高精度参考影像进行绝对几何定标,采用分步迭代的方法对参考基准波段影像内外定标参数进行解算,其次进行波段间相对几何定标,最后得到所有波段影像的几何定标结果。实验结果表明,经在轨几何定标后,平面无控定位精度优于5个像元,影像几何质量得到明显改善,说明所采用的定标模型和方案合理有效。 相似文献
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针对传统三维声呐硬件系统复杂、计算量庞大的特点,本文设计了一种基于垂直线阵的水下三维成像系统。相比于传统二维面阵成像声呐,垂直线阵成像声呐阵元数较少,硬件电路较简单。但是,垂直线阵扫面时间过长的缺点使得系统成像速率较慢,无法满足实时成像的需求。为解决此问题,本文提出了一种多频率发射波束形成算法,该算法通过优化垂直阵列的发射过程,有效地减少了系统发射阵列的波束发射次数,从而缩短了系统扫描时间,提升了成像速度。系统硬件部分由发射模块、接收模块、电源模块以及显示模块4个部分组成。系统通过FPGA控制120路信号的同步采样,在波束形成计算中使用并行子阵分级波束形成算法再次提高了系统的运算速率。为了验证系统的性能指标,本文先后对系统进行了波束形成仿真测试以及水下环境的实际成像测试。经测试,本文设计的垂直线阵三维声呐成像效果接近同等指标的二维面阵成像声呐,系统成像帧率较高,满足了三维声呐低功耗、小型化、实时成像的需求。 相似文献
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This paper describes the estimation of hydrodynamic coefficients and the control algorithm based on a nonlinear mathematical modeling for a test bed autonomous underwater vehicle (AUV) named by SNUUV I (Seoul National University Underwater Vehicle I).A six degree of freedom mathematical model for SNUUV I is derived with linear and nonlinear hydrodynamic coefficients, which are estimated with the help of a potential code and also the system identification using multi-variable regression.A navigation algorithm is developed using three ranging sonars, pressure sensor and two inclinometers keeping towing tank applications in mind. Based on the mathematical model, a simulation program using a model-based control algorithm is designed for heading control and wall following control of SNUUV I.It is demonstrated numerically that the navigation system together with controller guides the vehicle to follow the desired heading and path with a sufficient accuracy. Therefore the model-based control algorithm can be designed efficiently using the system identification method based on vehicle motion experiments with the appropriate navigation system. 相似文献
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This paper describes a new framework for detection and tracking of underwater pipeline,which includes software system and hardware system.It is designed for vision system of AUV based on monocular CCD camera.First,the real-time data flow from image capture card is pre-processed and pipeline features are extracted for navigation.The region saturation degree is advanced to remove false edge point group after Sobel operation.An appropriate way is proposed to clear the disturbance around the peak point in the process of Hough transform.Second,the continuity of pipeline layout is taken into account to improve the efficiency of line extraction.Once the line information has been obtained,the reference zone is predicted by Kalman filter.It denotes the possible appearance position of the pipeline in the image.Kalman filter is used to estimate this position in next frame so that the information of pipeline of each frame can be known in advance.Results obtained on real optic vision data in tank experiment are displayed and discussed.They show that the proposed system can detect and track the underwater pipeline online,and is effective and feasible. 相似文献
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赤潮藻的显微图形测量方法研究 总被引:2,自引:0,他引:2
介绍了一种在实验室环境下通过显微镜及CCD成像的办法观察采集微小藻类图像,并通过计算机软件进行图像识别统计,最终得到所测藻类统计信息的方法。 相似文献
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Motivated by the desire to improve the navigation performance of small autonomous underwater vehicles, we seek simple methods for modeling the local flow that affects the vehicle's trajectory. We propose a low-complexity, planar flow field model that consists of a uniform flow component and a singular flow component. Assuming this simplified flow field model, we develop identification algorithms that can be performed quickly using small, sparse data sets collected by a platoon of vehicles. The basic approach involves estimating the uniform flow component, localizing an assumed flow singularity, and identifying the parameters which characterize the singular flow. In order to identify the singular flow component, we propose a least squares and a constrained least squares approach. In the latter case, the minimization is constrained to preserve the average divergence and circulation of the measured flow. Preserving divergence and circulation predictably results in a larger overall error because it eliminates two free model parameters, but it produces a flow model which more realistically captures the flow in the larger region of the measurement points. Numerical simulations and an initial experiment illustrate the parameter identification process as well as the benefits of incorporating a flow field model for vehicle navigation. 相似文献
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厦门西港航道潮流和悬沙回淤实验研究 总被引:1,自引:0,他引:1
通过潮汐水流试验和定床浑水悬沙回淤试验,探求厦门西港嵩(屿)-鼓(鼓浪屿)水道及猴屿以南浅段航道水流动力特点及泥沙回淤机制,研究各种工程方案对航道及港区沙回淤规律的影响,预测港区航道今后泥沙回淤趋势。 相似文献
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It is shown that by implementing certain mine avoidance techniques, an underwater vehicle equipped with an obstacle avoidance sonar (OAS) and a navigation system can safely navigate an unknown minefield. The mine avoidance techniques take into account the physical limitations of the sonar and the navigation system, the maneuverability constraints on the underwater vehicle, and the required safe standoff distance from all mines. Extensive computer simulations have verified the mine avoidance capability in more than 50 different minefields. In all 50 simulations the vehicle reached a predetermined end point and maintained at least the specified, minimum safe standoff distance from each mine. The simulation accurately models the major difficulties associated with the sonar, the navigation system, and the vehicle dynamics. The sonar model includes surface, bottom, and volume reverberation; thermal, ambient, and flow noises; actual receiver and projector beam patterns; and false alarms and missed detections. The navigation system model contains the effects of biases, random noises, and scale factor errors. The vehicle dynamic model simulates angular velocities and accelerations associated with underwater vehicles 相似文献