共查询到19条相似文献，搜索用时 38 毫秒
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超短基线定位解算中的距离观测值是指换能器与水下应答器之间的直线距离,而海水声速的不均匀分布导致声波在海水中的实际传播路径为连续弯曲的曲线,需要结合实测声速剖面进行声线修正。根据声速在分层介质中的传播特性,本文提出了一种基于二次多项式拟合的声线跟踪算法,采用线性插值方法对声速剖面数据进行合理加密并按等深度进行分层,设定每层声速梯度是不断变化的,用二次多项式拟合声速,基于运动学原理建立了完整的数学解算模型。仿真结果表明,该方法修正后的水下目标分布具有明显的收敛性,且优于等梯度声线跟踪算法和等效声速剖面法,显著提高了超短基线水声定位系统的定位精度。 相似文献
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针对多波束常梯度声线跟踪计算耗时和声速剖面简化导致计算精度下降的问题,在对多波束常梯度声线跟踪理论进行分析的基础上,提出了一种基于时间分解的常梯度声线跟踪方法。将波束在层内的传播时间分解为与波束入射角无关的固定项和有关的变化项,固定项对于每个声速剖面仅需计算一次,对变化项采用麦克劳林公式展开得到其一阶近似,简化了层内传播时间和水平位移的计算;同时仅对变化项应用简化的声速剖面,降低剩余传播时间计算误差。实验结果证明当波束角小于50°、层间距小于50 m或上下层声速差小于20 m/s时,近似模型与常梯度算法精度相当,时间分解法在声速剖面层间距增大时能显著提高声线跟踪的精度。 相似文献
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水声定位系统中, 声线弯曲是造成定位误差大的主要原因, 本文针对该问题提出了一种迭代适应点分层(IAPL)的声线修正算法, 将声速剖面筛选分层修正声线。首先搭建水声定位模型, 通过拟合目标海域的监测数据, 得到声速高次函数; 其次探究声线弯曲时目标位置与掠射角的关联性, 由此构造出声线插值函数并求解路径参数; 最后提出划分原则, 精简声速剖面分层。仿真结果表明, 所提算法定位误差较低, 分层精简率均维持在48.04%的水平, 使计算量平均下降可达50.27%, 能够最大程度保留声速剖面的原始特征, 减少分层数量, 提高计算效率。 相似文献
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为解决声线跟踪精度与计算量之间的矛盾,在常梯度分层声线跟踪法的基础上,提出了一种适用于多波束测深的声线跟踪自适应分层方法,即利用Douglas-Peucker算法对原始声速剖面数据进行筛选分层。给出了不同阈值的分层结果,并对等间隔分层与自适应分层的声线跟踪结果进行了比较。实验结果表明,自适应分层法能够顾及到声速结构变化规律,有效提取声速变化节点,克服了人工选点的不足;在相同计算量情况下,自适应分层法声线跟踪精度要优于传统的等间隔分层法。本方法能够有效解决声线跟踪精度与计算量之间的矛盾,具有良好的工程应用价值。 相似文献
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海洋内波对水声场的扰动 总被引：4，自引：0，他引：4
针对海洋内波对水声传播影响的问题，在简要引出内波方程，水声方程和内波解，射线理论之后，以水深2100m等Vaisala频率的全板造波内波解对双线性水声剖面情况计算了内波和内波对声场及声线传播的影响，结果表明，内波对声线传播的路径和时间的影响是不可忽略的。 相似文献
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Dwight E. Boegeman Gordon J. Miller William R. Normark 《Marine Geophysical Researches》1972,1(4):381-396
The Marine Physical Laboratory of the Scripps Institution of Oceanography has developed an acoustic relay transponder for precise relative positioning of near-bottom instruments and geologic sampling devices. Although specifically designed to position equipment lowered on standard wire ropes without a need to maintain direct electrical contact with the surface ship, the relay transponder may be used to track free vehicles, such as deep submersibles, from the surface. The relay transponder is positioned relative to an array of bottom-anchored acoustic transponders. It is interrogated acoustically from the surface ship; it then sequentially interrogates the bottom transponders which, in turn, reply to the ship. From the measurement of the total travel time (ship to relay transponder to bottom transponder to ship) and assuming, or knowing, the sound velocity of the water, we obtain a relayed range measurement. These relayed ranges, used in conjunction with ship to bottom-transponder ranges, allow us to calculate the position of the relay transponder. A recent application of this technique is described in which several gravity core samples from the crest of the Horizon Guyot were positioned with respect to the detailed bathymetry and the geology within the area. The estimated error in positioning the samples is less than 20 m inside a navigational net extending over 100 km2.Contribution of the Scripps Institution of Oceanography, new series. 相似文献
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The accuracy of GPS/Acoustic positioning is crucial for monitoring seafloor crustal deformation. However, the slant range residual is currently the only indicator used to evaluate the precision of positioning seafloor transponders. This study employs a unique Seafloor Acoustic Transponder System (SATS) to evaluate the accuracy of GPS/Acoustic seafloor positioning. The SATS has three transponders and an attitude sensor in a single unit, which provides true lengths of transponder baselines and true attitude of the SATS to ensure assessment reliability and validity. The proposed approach was tested through a GPS/Acoustic experiment, in which an off-the-shelf acoustic system was used to collect range measurements. Using GPS/Acoustic geodetic observations, the positions of three transponders on the SATS were estimated by an optimization technique combined with ray-tracing calculations. The accuracy of the GPS/Acoustic seafloor positioning is assessed by comparing the true baselines and attitude with the results derived from the position estimates of the three transponders. A sensitivity analysis is conducted to investigate the robustness of the GPS/Acoustic positioning results to changes of sound speed. Experimental results demonstrate that the use of the SATS can help to assess the validity of the GPS and acoustic travel time measurements in the GPS/Acoustic seafloor positioning. 相似文献
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F. N. Spiess 《Marine Geodesy》2013,36(4):385-398
Abstract A logical approach to large area sea floor strain measurement is to use a set of precision acoustic transponders interrogated successively from a large number of different positions by a near‐bottom survey vehicle. Limiting errors in such an approach can be segregated into two classes implying two different scales on which averaging should be carried out. First are those arising from individual travel time and vehicle depth measurements. Second are those associated with imperfect knowledge of the sound propagation speed. The first are essentially independent from one measurement to the next; for the second, statistically independent observations must be separated by the order of 100 m. Several thousand observations of successive travel times to individual transponders would thus be smoothed to produce the equivalent of a smaller number (few hundred) of sets of simultaneous range observations, and then these sets would be used to determine the transponder array geometry. Computer simulations using realistic assumptions show that centimeter‐level accuracy can be achieved over areas several kilometers across. 相似文献
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Absolute positioning of an autonomous underwater vehicle using GPS and acoustic measurements 总被引：2，自引：0，他引：2
Kinematic global positioning system (GPS) positioning and underwater acoustic ranging can combine to locate an autonomous underwater vehicle (AUV) with an accuracy of /spl plusmn/30cm (2-/spl sigma/) in the global International Terrestrial Reference Frame 2000 (ITRF2000). An array of three precision transponders, separated by approximately 700 m, was established on the seafloor in 300-m-deep waters off San Diego. Each transponder's horizontal position was determined with an accuracy of /spl plusmn/8 cm (2-/spl sigma/) by measuring two-way travel times with microsecond resolution between transponders and a shipboard transducer, positioned to /spl plusmn/10 cm (2-/spl sigma/) in ITRF2000 coordinates with GPS, as the ship circled each seafloor unit. Travel times measured from AUV to ship and from AUV to transponders to ship were differenced and combined with AUV depth from a pressure gauge to estimate ITRF2000 positions of the AUV to /spl plusmn/1 m (2-/spl sigma/). Simulations show that /spl plusmn/30 cm (2-/spl sigma/) absolute positioning of the AUV can be realized by replacing the time-difference approach with directly measured two-way travel times between AUV and seafloor transponders. Submeter absolute positioning of underwater vehicles in water depths up to several thousand meters is practical. The limiting factor is knowledge of near-surface sound speed which degrades the precision to which transponders can be located in the ITRF2000 frame. 相似文献
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The GNSS-Acoustics (GNSS-A) method couples acoustics with GNSS to allow the precise localization of a seafloor reference in a global frame. This method can extend on-shore GNSS networks and allows the monitoring of hazardous oceanic tectonic phenomena. The goal of this study is to test the influence of both acoustics ray tracing techniques and spatial heterogeneities of acoustic wave speed on positioning accuracy. We test three different ray tracing methods: the eikonal method (3D sound speed field), the Snell-Descartes method (2D sound speed profile), and an equivalent sound speed method. We also compare the processing execution time. The eikonal method is compatible with the Snell-Descartes method (by up to 10 ppm in term of propagation time difference) but takes approximately a thousand times longer to run. We used the 3D eikonal ray tracing to characterize the influence of a lateral sound speed gradient on acoustic ray propagation and positioning accuracy. For a deep water (? 3,000 m) situation, frequent in subduction zones such as the Lesser Antilles, not accounting for lateral sound speed gradients can induce an error of up to 5 cm in the horizontal positioning of a seafloor transponder, even when the GNSS-A measurements are made over the barycenter of a seafloor transponder array. 相似文献
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Dosso S.E. Brooke G.H. Kilistoff S.J. Sotirin B.J. McDonald V.K. Fallat M.R. Collison N.E. 《Oceanic Engineering, IEEE Journal of》1998,23(4):365-379
Array element localization (AEL) surveys are often required to accurately localize acoustic instruments (transponders or sensors) in the ocean. These are typically based on transmitting or recording acoustic signals from or at a set of well-known positions. A significant limiting factor in many AEL surveys is the uncertainty inherent in these “known” positions. In this paper, an inversion algorithm is developed which properly treats both transponder and sensor positions as unknowns, subject to available a priori information in the form of position estimates and uncertainties. The algorithm essentially consists of an iterative linearized inversion of the raytracing equations employing the method of regularization. The approach is applied to independently localize transponders and vertical line array (VLA) sensors that form part of a three-dimensional sensor array in the Arctic Ocean. Confidence limits estimated via Monte Carlo simulation indicate that transponders and sensors are localized to less than 1 m in three dimensions. The VLA sensor motion, monitored over a seven-week period, appears to be predominately driven by tidal currents and is consistent with historical current measurements for the region 相似文献
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Traditional Global Navigation Satellite System-Acoustic (GNSS-A) positioning assumes the Layered Model in the sound speed structure, and any of horizontal perturbation of seawater degrades its accuracy. However, the use of the Gradient Model analytically demonstrated that the horizontal gradient of the sound speed structure and displacement can simultaneously be solved using multiple transponders for each of ping. We applied this technique to our observed data and found it unsuitable for real data. We confirmed that a horizontal perturbation with wavelength shorter than the horizontal extent of the transponder array significantly violates the linear approximation in the Gradient Model. Our vertical 2D numerical simulation of internal waves (IWs) forced by tidal oscillation showed that such small-scale IWs could effectively be generated by nonlinear cascade from large-scale IWs of the major tidal constituents. In addition, a small-scale IW in deep water typically has a period of 3–4 h, which degrades positioning accuracy significantly, whereas an IW of much shorter period in shallow water has less effect after removal of the fluctuation by time averaging within a typical observation period. Apparent array position obtained in the synthetic test based on the simulated IW-derived sound speed structure showed features quite similar to that observed in real surveys. To incorporate such deeper perturbation, we proposed a Disturbance Model using dual sea surface platforms, that can solve time-varying perturbation in the vicinity of each transponder.
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