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1.
准确计算珊瑚礁的面积是评估其资源、环境效应的基础,但我国迄今对南海珊瑚礁的面积估算仍缺乏共识,缺少可靠的估算方法是导致这一现象的重要原因。针对这一问题,本文以西沙群岛羚羊礁为例,提出了一种利用多时相多光谱遥感影像低成本半自动化估算珊瑚礁面积的方法。首先快速目视确定地貌带分界线的粗略位置,然后利用基于梯度向量场的主动轮廓线模型（Gradient Vector Flow-Snake, GVF-Snake）实现这些分界线位置的自动精化,最后将不同时相的瞬时分界线转换为面要素进行多时相的融合,从而得到珊瑚礁的面积。基于53景Sentinel-2 多光谱成像仪（MSI）影像的实验表明,羚羊礁的总面积为17.22 km2（Landsat 8 陆地成像仪（OLI）用于方法稳定性的验证,得到的羚羊礁面积为17.29 km2）,其中礁前斜坡、礁坪?潟湖坡、潟湖的面积分别为1.76 km2、10.29 km2、5.17 km2。该数值与实测数据具有较好的一致性。具体地,该方法获得的地貌带分界点与实测水深所指示分界点的位置偏差能控制在0.2～4.9 m的范围内（不超过0.5个像素）,珊瑚礁最外轮廓线与30 m等深线的位置偏差亦在1个像素大小内（5.7～9.5 m）,而估算面积与高分辨率WorldView-2影像解译得到的面积差异为0.02%。同时,该方法获得的珊瑚礁边界线的完整度、正确度、提取质量精度能够由单时相平均的60%、64%和54%分别提高至84%、83%和72%。此外,该方法能够减小基于不同遥感数据源的珊瑚礁面积估算结果的差异,即6景以上的多时相Sentinel-2 MSI和Landsat 8 OLI影像提取的珊瑚礁面积标准差分别不超过0.01 km2和0.05 km2,仅相当于珊瑚礁总面积的0.2%和0.5%。总而言之,该方法能够用低成本的10 m分辨率Sentinel-2 MSI和30 m分辨率Landsat 8 OLI影像获得接近1.8 m分辨率WorldView-2影像的面积估算精度,且具有良好的稳定性和可靠性。 相似文献
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为利用遥感技术快速、及时的掌握厦门近岸海域水体中悬浮颗粒物的总体分布情况,现场测量了厦门海域水体的下行入射辐射、天空光以及经过水气界面后反射回的辐射,计算了该海域水体表面的离水辐射获得了水体表面以上遥感反射率;同时采集了与光谱信息同步的水体样品,并分析了水体中的悬浮颗粒物质量浓度,获取了对应站位的水体反射波谱曲线和采集样品的浓度数据.通过研究不同站位水体的反射光谱数据,依据GF-WFV波段设置,对现场实测的光谱数据进行了拟合,并创建了基于GF-WFV拟合波段的悬浮颗粒物浓度经验反演算法.通过研究发现拟合(Rrs3+Rrs4)/Rrs2(其中Rrs1、Rrs2、Rrs3、Rrs4分别是GF-WFV第1、2、3、4波段的遥感反射率)同实测水体悬浮颗粒物质量浓度之间的决定系数为0.655,依据研究得出的反演算法反演该海域水体悬浮颗粒物质量浓度,其均方根误差为11.03 mg/dm3,相对误差为8.40 mg/dm3.利用同步的GF-WFV遥感数据对厦门近岸水体中总悬浮颗粒物质量浓度进行了研究,获取了研究区水体悬浮颗粒物的空间分布情况,结果表明GF-WFV遥感数据能很好的反映厦门近岸水体悬浮颗粒物浓度分布状况. 相似文献
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总悬浮物浓度是海洋的重要水质参数之一,其对水体透明度、水下光场及初级生产力有显著影响,同时对河流入海口与海岸带冲淤变化过程有重要作用。本文基于我国自主研制的SDGSAT-1卫星遥感影像,使用准分析算法（Quasi-Analytical Algorithm,QAA）获取水体固有光学量,并结合2022年4月黄河口区域总悬浮物浓度实测数据,建立水体固有光学量与总悬浮物浓度实测数据的单波段、波段加减、波段比值,以及多波段组合等模型并开展遥感反演,最后将反演结果同实测数据及基于Sentinel-2B影像的总悬浮物浓度反演结果进行对比。研究结果表明：基于SDGSAT-1影像的总悬浮物浓度反演结果在黄河口高浓度区域的决定系数为0.622,均方根误差为7.94 mg/L;基于Sentinel-2B影像的总悬浮物浓度反演结果在黄河口高浓度区域的决定系数为0.589,均方根误差为8.27 mg/L。故在我国近岸海域总悬浮物浓度反演方面,SDGSAT-1影像反演精度与Sentinel-2B影像反演精度相媲美。 相似文献
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采用星星交叉检验方法,比对了VIIRS和MODIS在中国渤海遥感反射率获取能力。由对比结果得出:在近岸海区VIIRS和MODIS观测能力相似,在浑浊水体VIIRS的遥感反射率高于MODIS。同时基于2012年9月辽东湾航次获取的现场遥感反射率数据对VIIRS在渤海海区的反演能力进行了星地检验。结果表明:VIIRS在中国近岸二类水体的反演效果较好,但出现了低估现象,在反演精度上,VIIRS卫星Rrs产品的反演误差远离近红外波段而增大,随水体悬浮颗粒浓度的增加而增大。 相似文献
5.
以内陆水体为观测目标的GF-1影像常规融合方法评价 总被引：1，自引：0，他引：1
内陆水体的研究需要遥感影像具备高空间分辨率和高光谱分辨率，这使得影像的全色（PAN）波段和多光谱（MS）波段之间的融合尤为重要。本文以钱塘江大缺口段为研究对象，采用四种常规融合方法，包括Pan Sharpening（PS）、主成分分析（PCA）、Gram Schmidt（GS）和小波分析（WF），分别对GF-1影像开展了全色波段和多光谱波段的融合方法评价。研究结果表明，GS融合后的影像效果最好，随后分别是PCA、WF和PS。由于水陆之间反射率信息获取的根本差异，大面积水体的存在会影响到融合影像保留源图像空间和光谱信息的能力。因而，在进行遥感影像融合时，融合方法的选择需要考虑影像中水域面积的分布情况。 相似文献
6.
为了能够利用遥感图像快速准确地提取围海养殖矢量信息,本文选取养殖水体、堤坝及育苗室等交错分布的海参围海养殖区域作为研究区域,根据研究区域Sentinel-2遥感影像的光谱特征,选用归一化差异水体指数（Normalized Difference Water Index,NDWI）、改进归一化差异水体指数（Modified Normalized Difference Water Index,MNDWI）和增强水体指数（Enhanced Water Index,EWI）三类水体指数,分别进行提取实验,利用同时期高空间分辨率的高分二号卫星（GF-2）影像作为参考,验证不同方法的提取精度,精度评价结果表明：相较MNDWI和EWI两类水体指数,NDWI的分类精度更高,且利用NDWI提取研究区域的围海养殖信息的效果更好,所以该方法可在养殖区域的动态监测和规划管理中发挥数据支撑作用。 相似文献
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基于Radarsat-2全极化SAR、GF-1多光谱、Landsat-8多光谱影像,利用PCA变换、HSV变换等方法,分析了同空间分辨率的SAR与光学全色影像的信息量,并评价了其分别与Landsat-8多光谱影像的融合结果。结果表明:全极化SAR影像较全色影像的亮度高,图像标准差、信息熵及平均梯度总体趋于一致,信息量相当;融合影像目视效果相近,且SAR融合影像较光学融合影像包含的信息量更为丰富,利用高分全极化SAR影像替代光学全色影像开展海岸带遥感监测是可行的。 相似文献
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文章利用舟山近岸海域实测水体光谱及泥沙浓度数据，分析光谱反射率与悬浮泥沙浓度的相关性，并结合Landsat8遥感数据进行该海域的悬浮泥沙浓度遥感反演。研究表明：随着水体悬浮泥沙浓度的增加，各波段的反射率相应增加，且不同波段的增幅有明显不同，水体光谱曲线存在“双峰”现象；Landsat8遥感数据的波段4与波段3的比值与悬浮泥沙浓度的相关性较好；舟山群岛海域总体处于高泥沙浓度的状态，岛屿近岸悬浮泥沙浓度明显高于开阔水域，岛屿周围的悬浮泥沙浓度呈现“西高东低”的格局；一元二次方程模型（二次模型）对舟山海域水体的悬浮泥沙浓度反演精度较其他模型（线性模型，对数模型，指数模型，幂指数模型）高；Landsat8遥感数据可用于舟山海域悬浮泥沙浓度的监测。本研究成果能为近岸海域港口建设、航道安全、环境监测等研究提供数据支持。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
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The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
19.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献
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The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献