Effects of Bathymetric Grid-Cell Sizes on Habitat Suitability Analysis of Cold-water Gorgonian Corals on Seamounts

We investigated the effects of the spatial resolution of bathymetry data on the predicted local distribution of large gorgonian corals on the southern Emperor Seamounts in the high seas of North Pacific. Terrain attributes were calculated from bathymetric survey data at six different grid-cell sizes (25–800 m) to investigate how the values of bottom terrain attributes and the prediction of MaxEnt habitat suitability models would vary with grid-cell size. The values of each terrain attribute showed different patterns among different grid-cell sizes, and MaxEnt demonstrated better performance at grid-cell size of 100 m or less than at larger sizes.     

Gravitational effect of distant Earth relief within the territory of former Czechoslovakia

We analyzed the gravitational effect of topography and bathymetry beyond the angular distance of approximately 1.5 degrees (referred to as the distant relief effect or DRE), and its impact on measured gravity values in the region of the former Czechoslovakia. Our work was strongly motivated by the contents of the pioneering contribution of outstanding Czech geophysicists Miloš Pick, Jan Pícha and Vincenc Vyskočil, which appeared at the turn of the 1950’s and 1960’s. Our numerical calculations were based upon the direct evaluation of the gravitational effects of compartments of a spherical layer, while the respective heights and depths were obtained from the 2 × 2 minutes digital elevation model (DEM) ETOPO2, taking into consideration also the influence of distant bathymetry. Our results are in close agreement with, but not identical to, those of the above cited authors. We also analyzed the influence of the grid cell size of the involved DEM upon the calculation results. We introduced an approximation of the analyzed effect, based on a simple linear relationship between the calculation point height, the DRE and its vertical gradient (VGDRE). Since when calculated at zero elevation the involved quantities DRE and VGDRE are smooth functions of latitude and longitude and can be easily interpolated, the approximation gives acceptable results in terms of desired accuracy of several μGal (1 μGal = 10⁻⁸ m/s²). In general, we can state that within the territories of the Czech and Slovak Republics the studied distant relief effect has negligible impact upon local gravity survey data. However, when applied to regional gravity studies, there could be a question of its possible influence in the form of a quasilinear W-E trend ranging approximately from −106.6 to −102.5 mGal within the territory of former Czechoslovakia. If we wanted to correct for this phenomenon, we should subtract this negative quantity from the standard Bouguer anomalies as they have been defined in the recent geophysical literature, thereby considerably increasing their values. But, instead of straightforward correcting the Bouguer anomalies for DRE only, we would rather recommend to wait until after the crustal and even lithospheric effects have been studied more carefully based upon the present day independent knowledge about the deep seated sources of those effects.     

多子阵幅度-相位联合检测法在多波束测深系统中的应用

多波束测深系统中经常使用幅度法或相位法来进行海底检测,并且按某种准则来选择,但如果选择错误,可能会带来不可预测的误差。提出了一种多子阵幅度一相位联合检测法,同时利用海底回波信号的幅度和相位信息,综合了幅度法和相位法的优点,不但实现了超宽覆盖,而且改善了检测性能。利用仿真数据和海试数据对此方法进行了验证,得到了较好的结果。     

声惯一体单波束测深系统在长江河道勘测中的应用

现如今单波束测深系统及多波束测深系统已经在长江河道水下地形测绘中广泛应用,人们对于内河航道水下地形数据的精度要求也越来越高,声惯一体单波束测深系统很好地解决了传统单波束测深精度不高及多波束测深系统安装操作复杂且对测量水域条件要求较高等问题。本文针对声惯一体单波束测深系统在长江河道勘测中的实际应用情况,与传统单波束及多波束测量数据进行对比分析,结果表明声惯一体单波束测深系统能够很好地满足长江河道高精度测量的需求。     

CUBE算法及其在多波束数据处理中的应用

阐述了一种基于表面生成的多波束数据处理方法——CUBE(Combined Uncertainty and Bathymetry Estimator)算法,用该方法可以对观测区域网格节点"真实"水深及相关误差进行估计。与从测量水深中选择出"最佳"数据的手工交互方式的多波束数据编辑手段不同,CUBE算法具有很强的抗差性和较高的效率,适合于实时多波束数据处理。对南海某测区多波束数据处理结果表明,在没有人工干预的情况下,利用CUBE算法去噪生成的海底DTM图与手工编辑生成的相当吻合。CUBE算法和手工编辑方法综合对比得出,CUBE算法能够很好地保留水深地形细节,在计算效率、误差评估、实时处理等方面比手工编辑方法具有较大的优势。     

利用Bayes估计进行多波束测深异常数据探测

在海底地形变化连续、平缓的假设条件下,基于Bayes估计理论提出了多波束测深异常数据探测方法,并与选权迭代加权平均滤波法进行了分析和比较。结果证明,该方法可以解决测深异常值判断标准可靠性的问题,而且能合理、有效地探测出异常值。     

浅水多波束测深潮汐改正技术研究

提出了一种顾及潮时差变化的多验潮站多边形潮汐分区改正数学模型,设计了海量多波束数据通用的虚拟单验潮站改正模式。应用结果表明,该模型准确地再现了时变水位场,实现了区域瞬时海面的无缝拼接,较好地解决了多波束条带采用传统潮汐分区改正模型引起的断层及锯齿状问题。     

An Evaluation of Publicly Available Global Bathymetry Grids

We evaluate the strengths and weaknesses of six publicly available global bathymetry grids: DBDB2 (Digital Bathymetric Data Base; an ongoing project of the Naval Research Laboratory), ETOPO2 (Earth Topography; National Geophysical Data Center, 2001, ETOPO2 Global 2’ Elevations [CD-ROM]. Boulder, Colorado, USA: U.S. Department of Commerce, National Oceanic and Atmospheric Administration), GEBCO (General Bathymetric Charts of the Oceans; British Oceanographic Data Centre, 2003, Centenary Edition of the GEBCO Digital Atlas [CD-ROM] Published on behalf of the Intergovernmental Oceanographic Commission and the International Hydrographic Organization Liverpool, UK), GINA (Geographic Information Network of Alaska; Lindquist et al., 2004), Smith and Sandwell (1997), and S2004 (Smith, unpublished). The Smith and Sandwell grid, derived from satellite altimetry and ship data combined, provides high resolution mapping of the seafloor, even in remote regions. DBDB2, ETOPO2, GINA, and S2004 merge additional datasets with the Smith and Sandwell grid; but moving from a pixel to grid registration attenuates short wavelengths (<20 km) in the ETOPO2 and DBDB2 solutions. Short wavelengths in the GINA grid are also attenuated, but the cause is not known. ETOPO2 anomalies are offset to the northeast, due to a misregistration in both latitude and longitude. The GEBCO grid is interpolated from 500 m contours that were digitized from paper charts at 1:10 million scale, so it is artificially smooth; yet new efforts have captured additional information from shallow water contours on navigational charts. The S2004 grid merges the Smith and Sandwell grid with GEBCO over shallow depths and polar regions, and so is intended to capture the best of both products. Our evaluation makes the choice of which bathymetry grid to use a more informed one. The U.S. government right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.     

SEABEAM1185多波束系统的测量精度分析及在堤防监测中的应用

通过与不同型号单波束测深仪的多种方式和角度的比测试验，验证了SEABEAM 1185多波束测深系统具有全覆盖扫测，测量范围大、速度快，测深精度和分辨率高等优点，突出其可靠性和稳定性。介绍了SEABEAM 1185系统的组成及其技术性能，并具体分析了系统在监测广东省某河道堤防险段的使用情况及应用价值。     

用多波束系统对奥运帆船赛区进行水深地形测量的建议

2008年奥运帆船比赛将在青岛举行。预选赛场如何符合帆船比赛的要求?海底是否有影响运动员安全的障碍物7为此，建议对预选赛场海区进行多波束全覆盖水深地形测量。同时介绍了多波束测深系统的先进性以及在许多海洋工程中的应用。