共查询到20条相似文献，搜索用时 140 毫秒
1.
稳定性指标是海洋重力仪最重要的技术特性之一。针对国内对海洋重力仪稳定性测试与评估重视不够、数据处理过程欠规范、技术指标要求欠细化等现实问题,研究探讨了海洋重力仪稳定性测评的技术流程和数据处理方法,重点分析了环境因素和重力固体潮效应对测试结果的影响,提出了重力仪零点趋势性漂移、有色观测噪声与随机误差的分离方法,建立了比较完善的海洋重力仪稳定性评估指标体系,分析论证并进一步明确了重力仪零点漂移非线性变化的限定指标要求,为修订现行海洋重力测量作业标准提供了可靠的理论依据。 相似文献
2.
通过对两套德国生产的KSS31海洋重力仪十多年来的零点漂移变化观测数据的整理,分析了长期以来零点漂移特征及其影响因素。本文认为缓慢的正向漂移是海洋重力仪零点漂移之总体趋势,其中会出现一些正负的波动,而大的零点漂移波动往往对应着设备状态出现的大变化。建议在海洋重力仪的搬运、重新安装之后需加强监测;重力仪的恒温系统需长期保持工作状态;最后认为长期对海洋重力仪的零点漂移保持跟踪,对于海洋重力仪的维护、使用以及测量资料的精度保证十分必要。 相似文献
3.
4.
5.
稳定平台是海洋重力仪十分重要的组成部分,在测量中它能够为重力仪提供一个水平基准面,确保重力数据的质量。但在测量中,稳定平台倒台是常见故障,也是十分严重的故障,如不能及时维修,将会导致测量工作的中断。研究稳定平台倒台故障的原因及维修技巧,可为技术人员更好地掌握设备,有效排除仪器故障提供很好的帮助。稳定平台倒台故障的原因很多,以SⅡ型海洋重力仪为例,从介绍稳定平台的结构和工作原理出发,根据多年从事重力测量的工作经验,总结了稳定平台主要部件出现故障可能引起的倒台现象及原因,以及诊断故障的方法和维修技能。经实际应用,这些故障维修方法十分可靠和有效。 相似文献
6.
7.
8.
9.
在海上复杂的环境下进行重力测量,重力仪及技术人员的操作难免会出现各种各样的问题,导致测量的成果精度降低,甚至不符合规范要求。目前检查海洋重力测量成果质量的主要方法是内符合法,主要采用主测线、检测线交叉点的差值,或重复测线相邻点的差值来评估测量成果的质量。介绍了内符合法存在的弊端,比较了DTU重力数据与重力仪实测数据的精度,叙述了基于DTU重力数据检查海洋重力测量成果较大系统差的可行性,以模型数据为外符合数据源来检查实测成果的质量,作为内符合法的补充,是十分必要的。 相似文献
10.
采用测网交点差、重复测线和与KSS31-M型海洋重力仪重合测线对比的方法,利用近年来KSS32-M海洋重力仪的实测数据对KSS32-M海洋重力仪测量稳定性和数据可靠性进行分析。利用机动转向法验证重力仪阻尼延迟时间为70 s,基于70 s阻尼延迟时间计算的重力测网的测量准确度为0.65 m Gal,与KSS31-M型海洋重力仪采集的重力剖面对比结果看,重合测线相关性为高度相关,4条重合测线网的交点差绝对值最大为1.66 m Gal,准确度为0.59 m Gal,均达到国家标准要求的近海重力测网交点差均方根小于2 m Gal的技术指标。重复测线的幅值接近,相位吻合,匹配测点异常差的平均值小于0.9,均方根均小于0.8,相关性均在0.98以上。本研究表明KSS32-M型海洋重力仪动态测量性能稳定、测量数据可靠。 相似文献
11.
J.A. Pinkster 《Ocean Engineering》1979,6(6):593-615
A recently developed method, based on three-dimensional potential theory, to compute the mean wave drifting forces on a free floating structure in regular waves, is extended to include low frequency oscillatory components which arise when the structure is floating in regular wave groups consisting of two regular waves with small difference frequency. This completes the information necessary for the determination of the wave drifting forces under arbitrary irregular wave conditions.In regular wave groups the drifting forces not only depend on the first order velocity potential and the first body motions, but also on the wave exciting forces due to the low frequency part of the second order potential. For the general three-dimensional case the latter contribution can only be determined numerically and at the expense of long computation times. Since this contribution is generally not large compared to components which may be determined using linear potential theory it is included using a simple approximation. Results of the method of approximation are compared with some two-dimensional cases for which exact solutions are known.Results of computations of the total mean and low frequency surge forces on a rectangular barge and a column stabilized semi-submersible platform are presented. For both structures, the computed mean surge drifting forces in regular head waves are compared with results of model tests.The computed components of the total mean drifting forces are presented. It appears that for both the barge and the semi-submersible the same components are of importance.For the semi-submersible, the computed low frequency second order surge forces in head waves are compared with results obtained from a test in irregular head waves using cross-bispectral analysis methods. 相似文献
12.
V. I. Remchukov 《Physical Oceanography》1990,1(3):225-230
In situ observations of the movement of a current meter attached to a long cable system of a drifting research vessel are discussed. A method is suggested which allows the cable configuration to be restored using measurement data on tangent orientation with respect to the given points. The compiled data indicate that the elements of the cable system shift by dozens of metres with a speed of the order of tens of cm per second. These shifts account for about 90% of the estimated value of current velocity energy pulsations in the frequency band corresponding to the proper frequency oscillations of the current meter and of the vessel's roll and-and-pitch motions.Translated by V. Puchkin. 相似文献
13.
叶绿素浓度是衡量海洋浮游植物丰度的重要指标,快速准确地测定海水中的叶绿素含量,对于业务化监测和科学研究都具有重要的现实意义。基于活体荧光法的叶绿素传感器操作简便,可长期原位在线监测,能轻易获取大量实测数据,是当前海水叶绿素高精度测量手段的主要发展趋势。由于在海上应用时受到多种环境因素的影响,叶绿素传感器数据与实验室萃取法数值之间存在较大偏差。作者综述了科学界在浊度、光照、温度、盐度等海洋环境因素及藻类生理因素对叶绿素传感器测量的影响规律、影响机理和数据校正方法的研究进展,并对活体荧光法叶绿素传感器海上应用数据质量控制方法的研究思路进行了展望。 相似文献
14.
Wind-induced drift of objects at sea: The leeway field method 总被引：3，自引：0，他引：3
Øyvind Breivik Arthur A. AllenChristophe Maisondieu Jens Christian Roth 《Applied Ocean Research》2011,33(2):100-109
A method for conducting leeway field experiments to establish the drift properties of small objects (0.1-25 m) is described. The objective is to define a standardized and unambiguous procedure for condensing the drift properties down to a set of coefficients that may be incorporated into existing stochastic trajectory forecast models for drifting objects of concern to search and rescue operations and other activities involving vessels lost at sea such as containers with hazardous material.An operational definition of the slip or wind and wave-induced motion of a drifting object relative to the ambient current is proposed. This definition taken together with a strict adherence to a 10 m wind speed allows us to refer unambiguously to the leeway of a drifting object. We recommend that all objects if possible be studied using what we term the direct method, where the object’s leeway is studied directly using an attached current meter.We establish a minimum set of parameters that should be estimated for a drifting object for it to be included in the operational forecast models used for prediction of search areas for drifting objects.We divide drifting objects into four categories, depending on their size. For the smaller objects (less than 0.5 m), an indirect method of measuring the object’s motion relative to the ambient current must be used. For larger objects, direct measurement of the motion through the near-surface water masses is strongly recommended. Larger objects are categorized according to the ability to attach current meters and wind monitoring systems to them.The leeway field method proposed here is illustrated with results from field work where three objects were studied in their distress configuration; a 1:3.3 sized model of a 40-foot Shipping container, a World War II mine and a 220 l (55-gallon) oil drum. 相似文献
15.
Precise Multibeam Acoustic Bathymetry 总被引：7，自引：0，他引：7
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. 相似文献
16.
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. 相似文献
17.
Existing methods for the determination of the various forms of iodine present in seawater are laborious or unwieldy in use. This paper describes modified forms of the iodate and total iodine methods described by Barkley and Thompson (1960), a spectrophotometric procedure for iodate determination derived from Johannesson's (1958) work, and an automatic method for total iodine determination. Procedures for iodate and total-iodine determination which are suitable for use aboard ship, are recommended. Both procedures for iodate determination returned a standard deviation close to 0.5 μg/l when several replicate samples of a seawater containing approximately 30 μg/l of iodate-iodine were analysed. The automatic method for total iodine determination yielded a standard deviation of 0.8 μg/l by the repeated analysis of a seawater containing a total of approximately 50 μg/l of iodine. Suitable methods for the filtration and storage of seawater are also described. 相似文献
18.
Studies in waterbodies with peculiar salinity face problems in determining water salinity (mineralization). The conventional methods of determining salinity from conductivity or, in the past, chlorinity can yield significant errors. This article compares two methods for determining water salinity: the solid residue method and the measurement of sound velocity in water. It has been shown that the measurement of sound velocity (and temperature) can be used for reliable in situ determination of water salinity that is almost unfeasible by other methods (applicable only under laboratory conditions or yielding insufficient accuracy). Results of water salinity determination in different regions of the Aral Sea in 2012–2015 are presented. 相似文献
19.
针对多波束测量声速剖面采样间隔合理选取问题,首先介绍了常声速分层声线跟踪法与常梯度分层声线跟踪法基本原理及实现方式,其次基于两种声线跟踪方法分析了声速剖面采样间隔对多波束测深的影响规律,并利用三次样条插值法对声速剖面进行了层化处理以获取不同采样间隔声剖数据,最后结合限差要求,对采样间隔进行了优化选取,实验结果表明,常声速分层声线跟踪法较常梯度分层声线跟踪法对声剖采样间隔更为敏感,在给定限差范围内合理确定采样间隔,既能保证测量的精度又能提高算法运行效率,分析结果对多波束测深数据采集质量的实时监控和实时声线跟踪具有一定指导作用。 相似文献
20.
AbstractThe relocation of ocean bottom seismometers (OBSs) is a key step in analyzing the three-dimensional seismic tomographic structure of crust and mantle. In order to get the accurate location of OBSs on the seafloor, we analyze the travel times of direct water waves emitted by air-guns. The Monte Carlo and least square methods have been adopted to calculate the true OBS location. The secondary time correction is necessary if the arrivals of direct water waves show overall time drift during relocation which maybe originates from remnant of linear clock drift correction and average errors of travel time picking, mean water velocity assumption, and experiment geometry. We have improved the original OBS relocation procedure which we used previously for other experiments by deliberateness of a secondary time correction and automatically approaching the really mean water velocity. A series of synthetic tests are carried out firstly to document the feasibility of our procedure and then it is applied on a real experiment. In here, we relocate 28 OBSs in total were relocated in 3D seismic survey near Bashi Channel. Relocation results show that the drifting distances for the 28 OBSs range from 65 to 1136 m between the deployed and relocated locations deduced by relocation results. The Pearson correlation coefficient between OBS drifting direction and sea current direction is 0.79, indicating that the two sets of data are highly linearly related and further manifest the sea current as the most possible driving force for OBS drifting during landing on the seafloor but its detailed influence mechanism is unclear by now. This research is necessary and critical for velocity structure modeling, and the optimal relocation program provides valuable experiences for 3D seismic survey in other area. 相似文献