多波束测深系统的验收试验与数据分析

本文介绍了多波束测深系统验收试验方案的制定、实施及数据分析,为多波束用户提供一整套实用的系统验收试验方法。     

多波束测深声呐成像仿真及作用距离分析

AUV 等无人装备研制过程中如何选择合适的多波束测深系统以满足特定作业场景需求是工程技术人员关心的问题之一。从多波束测深声呐系统与 AUV 等无人系统的匹配角度出发,采用混响背景下的主动声呐方程建立了不同工作频率多波束作用距离计算评估方法,对 100 kHz~500 kHz 的多波束测深声呐作用距离进行了计算对比。在此基础上,采用线性调频、FFT 波束形成、脉冲压缩、样条插值扩充目标角度、Rife 算法优化角度估计技术,建立了多波束测深声呐的成像仿真方法,并通过直线地形、台阶地形对多波束测深声呐的成像特点和测深分辨率进行了分析。主要结论：1）建立了一种多波束作用距离评估的方法,可用于指导无人装备用多波束测深声呐频率参数的选型;2）建立的多波束测深声呐仿真办法可以帮助工程技术人员更直观地理解多波束测深声呐的成像特点;3）通过仿真分析了 CW 信号与线性调频信号下的距离分辨率,可用于指导波束测深作业时的高度、信号参数设置。     

多波束测深系统的现状和发展趋势

介绍并分析了多波束系统的现状，阐述了系统的发展趋势。认为系统的研制基本成熟，未来的研究重点将倾向于数据处理和应用研究，最后也探讨了具体的研究方向。     

多波束测深系统声速校正

海水声速是多波束测深系统进行水深测量的基本参数之一,声速剖面正确与否直接影响测量结果的精度和可靠性。声速校正为多波束测深系统提供了正确的声速剖面,根据声速剖面垂向上的变化规律,对原始声速数据进行科学采点,运用软件方法或实验方法对声速剖面进行编辑获得声速数据,最终取得合理可靠的水深值。这里对南海SA12试验区采集的声速资料进行了分析,以SeaBeam2100多波速测深系统为例,对声速校正的技术方法进行了探讨。     

SeaBeam2112多波束测深资料处理与解释

精确的海底地形测绘技术成果是人类研究海洋，开发海洋折基础，长期以来，我国海底地形测绘一直采用效率低，成图精度差的单波束回声测量技术，已远远不能满足当今研究海洋、开发海洋的需要，１９９４年地矿部广州海洋地质调查局引进美国ＳＥＡＢＥＡＭ公司生产的ＳｅａＢｅａｍ２１１２多波束测量系统是当今世界先进的海底地形，地貌多波速宽幅测量系统，本文介绍多波束测量系统的特点、功能及资料处理方法、流程和参数。     

多波束探测技术的应用

介绍多波束探测技术在港口、航道测量和水下物体搜寻等方面的具体应用实例，进一步说明多波束探测技术的高精度、高效率、高密度和全覆盖的特点，展望多波束在三峡工程中的应用前景，为三峡工程水下探测提供新的技术手段。     

多波束测深及影响精度的主要因素

通过多波束测深的基本原理、参数校正和数据改正方法的讨论,阐述了保证多波束测深精度的主要校改正方法,并在模型分析的基础上,探讨了声速剖面的结构及其时空变化对多波束测深精度的影响,指出了三个特征海区声速结构的分布特点,并提出了抑制三海区声速改正误差的可能方法及控制多波束测量中声速改正精度的措施     

基于多波束测深系统的水下成像技术

为实现多波束测深系统的一体化探测功能,研究分析了利用快拍法进行多波束水下成像的基本原理,并考虑实际中的水声环境和多波束测深系统自身的复杂性,对用于成像的位置数据和散射强度数据进行了修正,湖上试验数据的处理结果表明了该方法对水中目标的探测能力,验证了其工程应用的可行性。     

多波束测量边缘波束测深精度分析与评估

根据多波束测深系统边缘波束采集的异常数据云图,判别分析多波束测深系统的各误差源对边缘波束测深的影响,从理论上探讨声线折射所引起的测深误差与边缘波束角之间的关系,通过多波束测深工程实例的精度验证,结果表明:换能器安装的牢固程度和校准精度、测船定位和姿态改正与测深的时间同步性,对边缘波束的测深精度影响较大;声线剖面误差使得中央波束和边缘波束的测深偏浅或偏深,各波束的测深误差曲线呈现"哭脸"状或"笑脸"状,但对于各波束测深的综合精度,中央波束精度相对较高,两侧边缘波束精度相对较低。     

Precise Multibeam Acoustic Bathymetry

The maximum error in ocean depth measurement as specified by the International Hydrographic Organization is 1% for depth greater than 30m. Current acoustic multibeam bathymetric systems used for depth measurement are subject to errors from various sources which may significantly exceed this limit. The lack of sound speed profiles may be one significant source of error. Because of the limited ability of sound speed profile measurement, depth values are usually estimated using an assumed profile. If actual sound speed profiles are known, depth estimate errors can be corrected using ray-tracing methods. For depth measurements, the calculation of the location at which a sound pulse impinges on the sea bottom varies with the variation of the sound speed profile. We demonstrate that this location is almost unchanged for a family of sound speed profiles with the same surface value and the same area under them. Based on this observation, we can construct a simple constant-gradient equivalent sound speed profile to correct errors. Compared with ray-tracing methods, the equivalent sound speed profile method is more efficient. If a vertical depth is known (or independently measured), then depth correction for a multibeam system can be accomplished without knowledge of the actual sound speed profile. This leads to a new type of precise acoustic multibeam bathymetric system.     

Precise Multibeam Acoustic Bathymetry

The maximum error in ocean depth measurement as specified by the International Hydrographic Organization is 1% for depth greater than 30m. Current acoustic multibeam bathymetric systems used for depth measurement are subject to errors from various sources which may significantly exceed this limit. The lack of sound speed profiles may be one significant source of error. Because of the limited ability of sound speed profile measurement, depth values are usually estimated using an assumed profile. If actual sound speed profiles are known, depth estimate errors can be corrected using ray-tracing methods. For depth measurements, the calculation of the location at which a sound pulse impinges on the sea bottom varies with the variation of the sound speed profile. We demonstrate that this location is almost unchanged for a family of sound speed profiles with the same surface value and the same area under them. Based on this observation, we can construct a simple constant-gradient equivalent sound speed profile to correct errors. Compared with ray-tracing methods, the equivalent sound speed profile method is more efficient. If a vertical depth is known (or independently measured), then depth correction for a multibeam system can be accomplished without knowledge of the actual sound speed profile. This leads to a new type of precise acoustic multibeam bathymetric system.     

Analyzing Uncertainty in Multibeam Bathymetric Data and the Impact on Derived Seafloor Attributes

Multibeam bathymetric data provide critical information for the modeling of seabed geology and benthic biodiversity. The accuracy of these models depends on the accuracy of the bathymetric data, which contain uncertainties that are stochastic at individual soundings but exhibit a distinct spatial distribution with increasing magnitude from nadir to the outer beams. A restricted spatial randomness method that simulates both the stochastic and spatial characteristics of the data uncertainty performed better than a complete spatial randomness method in analyzing the impact of bathymetric data uncertainty on derived seafloor attributes.     

Processing Multibeam Backscatter Data

A new highly precise source of data has recently become available using multibeam sonar systems in hydrography. Multibeam sonar systems can provide hydrographic quality depth data as well as high-resolution seafloor sonar images. We utilize the seafloor backscatter strength data of each beam from multibeam sonar and the automatic classification technology so that we can get the seafloor type identification maps. In this article, analyzing all kinds of error effects in backscatter strength, data are based on the relationship between backscatter strength and seafloor types. We emphasize particularly analyzing the influences of local bottom slope and near nadir reflection in backscatter strength data. We also give the correction algorithms and results of these two influent factors. After processing the raw backscatter strength data and correcting error effects, we can get processed backscatter strength data which reflect the features of seafloor types only. Applying the processed backscatter strength data and mosaicked seafloor sonar images, we engage in seafloor classification and geomorphy interpretation in future research.     

Processing Multibeam Backscatter Data

A new highly precise source of data has recently become available using multibeam sonar systems in hydrography. Multibeam sonar systems can provide hydrographic quality depth data as well as high-resolution seafloor sonar images. We utilize the seafloor backscatter strength data of each beam from multibeam sonar and the automatic classification technology so that we can get the seafloor type identification maps. In this article, analyzing all kinds of error effects in backscatter strength, data are based on the relationship between backscatter strength and seafloor types. We emphasize particularly analyzing the influences of local bottom slope and near nadir reflection in backscatter strength data. We also give the correction algorithms and results of these two influent factors. After processing the raw backscatter strength data and correcting error effects, we can get processed backscatter strength data which reflect the features of seafloor types only. Applying the processed backscatter strength data and mosaicked seafloor sonar images, we engage in seafloor classification and geomorphy interpretation in future research.     

潮汐对多波束测深的影响及改正

讨论了潮汐对多波束测深的影响;通过分析验潮站控制及潮汐场解算的潮汐改正传统模式的特点,设计了该模式的工作流程;比较了传统改正模式与GPS无验潮模式的不同,研究了无验潮模式及陆海图拼接所涉及的垂直基准转换技术。     

利用UNIX平台对多波束测深系统进行监测

根据多波束测深系统存在着“工作站有时会停机”和“测深软件有时会退出”的问题,利用UNIX中的SHELL编写了两个程序,它们可以对多波束测深系统可能出现的故障进行实时监测。     

A Post-Processing Method for the Removal of Refraction Artifacts in Multibeam Bathymetry Data

Sound refraction artifacts are often present in multibeam swath bathymetry data. For a flat array, the artifacts are usually more serious in outer beams than in inner beams. In a 3D topographical mapping they appear as ridges that parallel the tracks of the vessel. To shorten the survey time, the outer beams should be utilized as often as possible. Therefore, the refraction errors should be removed. In this paper, we present a model of reduced sound speed profile that consists of three water layers. The sound speed of the two upper layers has a constant gradient, and the third layer has the same sound speed as the most bottom measured layer. The model parameters can be searched based on the principle of the minimum difference of depth between the overlap of two neighboring swaths. The horizontal position and depth of each beam can be accordingly recalculated using the model parameters. To avoid being trapped in local optimum, the initial search scope is limited according to assumed lunch angle and travel time in each subregion. The method is verified by comparing the simulated and real data.     

Robust Automatic Reduction of Multibeam Bathymetric Data Based on M-estimators

Multibeam echosounders have commonly been employed for a wide range of applications including offshore survey, navigation, hydrogeology, and oceanography. Because the tremendous volume of the bathymetric data is demanding for some purposes and requires significant storage space, the data reduction plays a prominent role in practice. Additionally, the multibeam soundings are inevitably contaminated with sporadic outliers, and as such, the data cleaning can be challenging especially in shallow waters. We present a speedily robust method for reliably reducing the volume of the bathymetric data within grid cells. In this respect, robust M-estimators are recursively applied to the data in a patch-wise manner to alleviate the undesirable effects of the outlying observations. Accordingly, the reduced bathymetry is automatically made unaffected by the possible outliers once their equivalent weights have been downweighted. The performance of the presented method has been demonstrated by synthetic datasets and an experimental dataset collected by an ATLAS FS 20/100 kHz shallow-water multibeam echosounder in the offshore waters of Kish wharf. The reliability, efficiency, and capability of the proposed method have been verified, which makes it quite possible to meet the IHO requirements for special-order seafloor mapping.     

多波束条带测深仪的动态测量误差评估

对于近年发展起来的多波束条带测深仪,其动态测量误差的评估是一项尚未完善解决的课题。本文提出了一种多波束条带测深仪动态测量误差的评估方法,并用海试结果证明了该方法的实用有效性。该方法可以推广应用到其它多波束测量声呐系统的动态测量误差分析与估计中。