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A dominant source of errors in swath bathymetry is acoustic interference. In 1989 the author published an analysis of these errors and predicted depth accuracies for a system which reduced their effect by averaging. This present paper shows how a considerable improvement in performance may be obtained by a variety of signal processing strategies that include the use of several widely spaced receivers and the elimination of the most unsatisfactory measurements before averaging. Simulations show how impressive sea bed profiles can be produced with a single ping, even at low signal-to-interference ratios 相似文献
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The authors discuss the current measurement accuracy of the RD Instruments 1200-kHz acoustic Doppler current profiler (ADCP) in the near surface and bottom boundaries. Data are presented from tests. In the first series of tests, an ADCP was mounted on a bottom sled in an upward looking mode. The sled was towed at known speeds with and without surface waves. Additionally, tests were conducted with several acoustic baffle designs installed in the transducer head. The 1200-kHz ADCP has the ability to accurately measure mean currents in a dynamic wave induced flow field. Sidelobes can bias the measurements at 85% of the range when bottom or surface boundaries are present. The amount of bias is strongly dependent on surface wave characteristics. Sidelobe bias can be eliminated with a properly designed baffle system. The profilers have the ability to measure wave particle velocities with a properly configured system 相似文献
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基于南海北部浮标和潜标的声学多普勒流速剖面仪（ADCP）数据,通过一套几何算法计算了台风海鸥（1415）期间ADCP的空间变化和流速误差,并进行数据校正。浮标上,台风过后ADCP的水平位移最大可达2.61 km,水平流速误差最大可达0.27 m/s,垂向流速误差最大仅为5×10-4 m/s;温跃层流速校正值在台风过后显著大于流速测值,这表明水平校正对于温跃层流速的质量控制很重要。潜标上,ADCP最大垂向位移增量为179 m,最大绳子倾角为35°,最大水平位移为1.5 km; ADCP水平流速误差和倾角误差都很小,在数据校正中可忽略不计,但对台风过后中层流速的垂向校正不能忽略。 相似文献
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为完善目前走航ADCP观测资料质量控制尚未形成统一流程的问题,将走航ADCP观测资料质量控制归纳为船速获取、声速校正、偏角校正以及剖面数据处理四个主要步骤,并制定了一套较为系统的走航ADCP观测资料质量控制流程。以渤海辽东湾红沿河核电站周边海域船载走航ADCP观测为例,按照提出的流程进行走航ADCP观测资料的质量控制。通过对比原始观测数据,质量控制后的结果表明u分量流速剔除了23.56%的低可信度数据,而v分量流速剔除了25.96%的低可信度数据。10 m与15 m水深处的质量控制前后的流速-频数直方图表明,本文提出的流程能有效地降低观测随机性的影响。 相似文献
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Fronts and strong currents of the upper southeast Indian Ocean 总被引：2，自引：1，他引：2
1 IntroductionBaroclinic component is the dominant part ofAntarcticCircum polarCurrent (ACC) (FandryandPillsbury,1979),and a baroclinictransportation asso-ciatedwithfrontsmakesupthem ajoritypartoftheto-talbaroclinictransportation oftheACC (Nowlin andCliff… 相似文献
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Frédéric Jourdin Caroline Tessier Pierre Le Hir Romaric Verney Michel Lunven Sophie Loyer André Lusven Jean-François Filipot Jérémy Lepesqueur 《Geo-Marine Letters》2014,34(4):381-397
A pair of self-contained acoustic Doppler current profilers (SC-ADCPs) operating with different frequencies were moored on a muddy sea bottom at about 20 m depth in the Bay of Vilaine off the French Atlantic coast. With their acoustic beams oriented upwards, the SC-ADCPs ensonified most of the water column. The results of several months of in situ recorded echo intensity data spanning 2 years (2003 to 2004) from the dual-frequency ADCPs are presented in this paper. The aim was to estimate suspended particle mass concentration and mean size. A concentration index CI is proposed for the estimation of particle concentration. Based on theory the CI—unlike the volume backscatter strength—does not depend on particle size. Compared with in situ optical data, the CI shows reasonable precision but not increased with respect to that of the highest-frequency backscatter strength. Concerning the mean particle size, despite a lack of quantitative validation with optical particle-size measurements, the method yielded a qualitative discrimination of mineral (small) and organic (large) particles. This supports the potential of dual-frequency ADCPs to quantitatively determine particle size. A cross-calibration of the transducers of each ADCP shows that a specific component of the precision of the backscatter strength measured by ADCP depends on the acoustic frequency, the cell thickness and the ensemble integration time. Based on these results, the use of two ADCPs operating with distinctly different frequencies (two octaves apart) or a single dual-frequency ADCP is recommended. 相似文献
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Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data 总被引：1，自引：0，他引：1
Variations of surface current velocity derived by the TOPEX altimeter are compared with data from Tokyo-Ogasawara Line Experiment (TOLEX)-Acoustic Doppler Current Profiler (ADCP) monitoring for a period from October 1992 to July 1993. Since the locations of ADCP ship track and TOPEX altimeter ground tracks do not coincide with each other, and the temporal and spatial sampling are also different between the ADCP and altimeter observations, re-sampling, interpolation and smoothing in time and space are needed to the ADCP and altimeter data. First, the interpolated TOPEX sea surface height is compared with sea level data at Chichijima in the Ogasawara Islands. It is found that aliasing caused by the tidal correction error for M2 constituent in the TOPEX data is significant. Therefore, comparison of the TOPEX data with the TOLEX-ADCP data is decided to be made by using cross-track velocity components of the surface current, which are considered to be relatively less affected by the errors in the tidal correction. The cross-track velocity variations derived from the TOPEX sea surface heights agree well with those of the ADCP observations. The altimeterderived velocity deviations associated with transition of the Kuroshio paths coincide with the ADCP data. It is quantitatively confirmed that the TOPEX altimeter is reliable to observe the synoptic variations of surface currents including fluctuations of the Kuroshio axis. 相似文献
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CODAS系统搭配相应质量控制参数,用以识别ADCP在复杂测流环境下测得的可疑或错误流速单元和剖面.通过水跟踪和底跟踪,CODAS系统可有效获取仪器自带数据处理软件vmdas、winriver无法修正的系统误差.本研究采用该系统对厦门湾走航ADCP测量数据做后续质量控制,所得相应系统误差如下：旋转角度偏差ΔФ=3.2°,幅值修正因子β=0.98.此外,以底跟踪测得流速为准确值,参考GPS数据经过系统误差订正后,流速精度显著提高,平均误差订正前后分别为28.9cm/s和11.6 cm/s.最后,结合现场数据采集工作与数据质量控制过程,总结数据质量问题一般特征并提出改进建议. 相似文献
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Masnadi-Shirazi M.A. de Moustier C. Cervenka P. Zisk S.H. 《Oceanic Engineering, IEEE Journal of》1992,17(3):239-251
A maximum-likelihood estimator is used to extract differential phase measurements from noisy seafloor echoes received at pairs of transducers mounted on either side of the SeaMARC II bathymetric sidescan sonar system. Carrier frequencies for each side are about 1 kHz apart, and echoes from a transmitted pulse 2 ms long are analyzed. For each side, phase difference sequences are derived from the full complex data consisting of base-banded and digitized quadrature components of the received echoes. With less bias and a lower variance, this method is shown to be more efficient than a uniform mean estimator. It also does not exhibit the angular or time ambiguities commonly found in the histogram method used in the SeaMARC II system. A figure for the estimation uncertainty of the phase difference is presented, and results are obtained for both real and simulated data. Based on this error estimate and an empirical verification derived through coherent ping stacking, a single filter length of 100 ms is chosen for data processing applications 相似文献
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Brumley B.H. Cabrera R.G. Deines K.L. Terray E.A. 《Oceanic Engineering, IEEE Journal of》1991,16(4):402-407
A new broadband acoustic Doppler current profiler (ADCP) is described, with a useful range comparable to that of a commercially available narrowband (incoherent) system of the same acoustic frequency, but having enhanced performance. The extra performance may be traded off among (1) reduced velocity variance, (2) reduced averaging time, and (3) finer depth resolution. This improvement permits the observation of phenomena with smaller time and space scales than is now possible with available ADCPs. An expression predicting r.m.s. velocity error in terms of system parameters and the measured acoustic data is given and is shown to be consistent with the independently measured velocity error among redundant beams. Two major sources of bias error in incoherent ADCPs are shown to be much reduced for the broadband system. Field data demonstrating the improved performance over the existing incoherent ADCP are shown for cases of both strong and weak shear 相似文献
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The currents in the Drake Passage are studied from the ADCP and CTD data acquired in a section across the Drake Passage in October-November of 2011 and from the satellite altimeter data. A complicated pattern of currents including eight jets of the Antarctic Circumpolar Current (ACC) and a system of slope and abyssal currents was found. The most interesting result is the discovery of several cyclonic and anticyclonic mesoscale eddies confined to the abyss. Some reasons explaining the generation of such eddies by the meandering of the ACC jets in the upper ocean layer are presented. 相似文献
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山东半岛北部海洋动力环境的高频地波雷达观测 总被引：1，自引：0，他引：1
利用两台高频地波雷达(ground wave radar,WERA)站对山东半岛北部雷达覆盖海区的浪、流场进行了观测,并且利用海洋-大气-波浪耦合沉积输运模型(coupled-ocean-atmosphere-wave-sediment transport modeling system,COAWST)对该区域的一个强风暴过程进行了数值模拟,对雷达观测数据、现场声学多普勒流速剖面仪(acoustic Doppler current profilers,ADCP)调查数据和数值模拟结果进行比对分析发现,模型模拟的水位变化与ADCP测量结果一致,WERA所观测到的有效波高和ADCP结果比较吻合,模型模拟的ADCP站位的流速相位、大小与雷达观测结果比较接近,与ADCP的结果有一定偏差。雷达观测的海区流场结果与模型反映趋势基本一致,但是在近岸方向上变化较大,其原因可能与ADCP的投放位置、模型的分辨率设置等因素有关。高频地波雷达系统是海岸带动力环境观测的一个有效工具,在实际应用中有着广泛的前景。 相似文献
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Bottom-penetrating sonar can be used to visualize large areas, for example by normal logging and printing of collected pings. In many applications, it is necessary to obtain an impression of three-dimensional (3-D) structures, but this is not easy because of the irregular spatial sampling due to coarse ship trajectories. Normally, the ping map and the ping data, cover only a very small part of a region of interest. In this paper, we describe a new method for interpolating irregularly spaced sonar data. The basic idea is to use a two-dimensional quadtree of the ping map in order to guide the 3-D interpolation process: since gaps between pings become smaller at higher tree levels, the volume can be filled by marking neighborhood relations in the quadtree and interpolating available pings when they become neighbors. Different marking schemes and their central processing unit times are compared. In the interpolation process, we apply cross correlations of ping data in order to construct continuity of sloping reflections. Our results show that excellent results can be obtained on real sonar data sets, even for volumes filled for less than 7%, for which processing times are reasonable even for large areas, and that the interpolated data can be used for volumetric interactive visualization. 相似文献
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ADCP measurements of suspended sediment flux at the entrance to Jiaozhou Bay, western Yellow Sea 总被引：1，自引：1，他引：0
The purpose of the present contribution is to explore the technique to use Acoustic Doppler Current Pro- filers （ADCPs） for suspended sediment flux measurements, which may be applied to coastal embayment environments such as estuaries and tidal inlets for sediment exchange and budget studies. Based on tidal cycle measurements from the entrance of ]iaozhou Bay, Shandong Peninsula, eastern China, statistical rela- tionships between the suspended sediment concentration （SSC） and ADCP echo intensity output are estab- lished. Echo intensity data obtained during an ADCP survey along two cross-sections during a spring tidal phase were transformed into SSC data. The ADCP current velocity and SSC data were then used to calculate the flux of fine-grained sediment. The results show that net sediment transport at the entrance is directed towards the open sea, with an order of magnitude of 103 t per spring tidal cycle; hence, although Jiaozhou Bay is a low SSC environment, the tidally induced suspended sediment transport can be intense. 相似文献