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在GPS测量作业中,GPS天线及差分数据链的作用十分重要。差分测量时参考台和移动台之间通信问题常使我们中止测量作业,也使我们感到这是一个需要急待解决弄清的问题。下面从理论及自己几年的工作实践谈一谈对GP3通讯链的了解及认识。 GPS通讯链部件包括:天线、通讯机、电缆。这三个部件中功效发挥好坏与否,受人为因素影响最大的,恰恰是被认为最简单的天线。因为天线种类、结构、使用方法等差异较大,加之人们往往对其重视不够,忽视天线的作用,只将它作为一根简单的导体,从而造成在通讯链中,发生在天线环节上的问题较为突出,因此天线问题在这里作为重点问题加以论述。 相似文献
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一种准确通用的台风路径预报模式 总被引:1,自引:0,他引:1
应用天气学理论,对台风云图的晴空区轴线制约台风移动的规律进行物理解释。根据台风云团与晴空区之间存在的干、湿梯度力和推动台风前进的惯性力的互相关系,建立台风移向预报方程和轨迹预报方程,分析论证了台风移向变化的物理过程,把影响台风移动的复杂因子转化为单一的预报因子。 相似文献
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《中国海洋大学学报(自然科学版)》2017,(2)
海洋波谱仪机载飞行试验通过对星载天线进行宽波束等效,能够测量海面后向散射系数,进而反演波浪谱及波浪参数。利用该系统在黄海中部进行飞行试验,对小入射角下波浪测量数据进行处理和分析,采用后向投影积分校正载机运动和天线旋转引起的越距离单元徙动,采用交叉谱方法降低斑点噪声,实现小海况下波浪谱反演,结果表明海洋波谱仪测量得到的波浪谱、有效波高、主波长、主波向等波浪参数与浮标、卫星同步测量吻合较好。 相似文献
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阐述了移动平台真风观测的实现原理,利用仪器观测到的相对风和船风的矢量关系获取实际的风向风速。首次设计外场车载试验方案,开展移动平台周围环境、移动速度、移动方式、风传感器安装位置等因素对真风观测影响的研究。船舶自动气象站研发阶段,通过车载试验验证移动平台真风观测算法的合理性,对算法不断改进,使真风更加接近观测事实。船舶自动气象站应用阶段,对船舶进出港时动态和静态真风数据,以及与航线附近海岛站观测的风进行对比分析,利用二者的均方根误差表征船舶站风和自动站风的误差大小,以此评估真风观测数据的可靠性。 相似文献
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D Parker SE Kerwath TF Næsje CJ Arendse FJ Keulder-Stenevik K Hutchings 《African Journal of Marine Science》2017,39(2):153-166
White stumpnose Rhabdosargus globiceps is the main target of the linefishery in Saldanha Bay. Increased fishing pressure over the last three decades, particularly by the recreational sector, has led to concerns regarding sustainability of the local white stumpnose stock. The fishery was exceptionally productive between 2006 and 2008, with an estimated annual catch of 141.2 tonnes (t). Only 3% of boat outings surveyed were commercial boats targeting white stumpnose, yet this sector accounted for 39.3 t (31%) of the average annual catch. The recreational boat sector accounted for most of the catch (70.0 t), and the recreational shore sector the least (31.9 t). Commercial boat catch per unit effort (CPUE; 3.7 fish angler–1 h–1) was more than 10 times that of recreational boats (0.3 fish angler–1 h–1). White stumpnose catch length-frequency differed significantly (p < 0.01) between the fishing sectors, with the commercial sector retaining larger fish (34.7 cm [SD 5.9]) than the recreational boat (33.9 cm [SD 5.9]) and shore (30.4 cm [SD 5.8]) sectors. A decline in commercial CPUE (2000–2015) of approximately 40% and a concomitant severe decline (>95%) in survey data for juvenile white stumpnose CPUE (2007–2016) indicate that the current rate of exploitation is not sustainable. Recovery of the white stumpnose stock will require a decrease in fishing mortality. Possible management regulations include sector-specific effort limitations, extending the ‘no take’ marine protected area, reducing the recreational-sector bag limit to 5 fish person–1 day–1, implementing a commercial-sector bag limit, and increasing the minimum size limit to 30 cm TL. 相似文献
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为了对海道测量中测线定位精度进行评估,以及为补偿测线系统误差的需要,提出了实测定位折线模型,同时在利用小波降噪算法求得拟合航迹线的基础上,提出了拟合定位测线的概念,针对测线的不同形态给出了拟合测线的另外两种模型,即拟合直线和拟合折线。仿真实验表明:提出的三种测线模型均满足1:2 000以下比例尺测图要求;在满足定位精度和测线正横水深梯度不超限的约束条件下,可以用拟合测线代替原始测线进行数据的后处理;三种测线模型对系统误差不存在"淹没效应";拟合折线可以方便地减弱测线内受方向、船速等系统误差的影响。 相似文献
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闭合导线测量中边长系统误差分析 总被引:1,自引:1,他引:0
在闭合导线测量中,导线边如果存在系统误差,其解算结果仍可能满足现行规范中的各项精度指标。通过一项边长接近的闭合导线测量实例,分析了产生误差的原因与对策,解算出符合要求的测量成果。 相似文献
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在天然气水合物勘探中,海底的泥底辟和泥火山构造是重要的研究对象。在高分辨率地震剖面解释中,直接识别泥底辟构造存在一定困难,主要表现为泥底辟构造和火成岩侵入体在形态上十分相似,容易造成解释的多解性。本文就目前天然气水合物调查中存在的这些特殊技术问题,通过对海上高精度磁力测量技术方法研究,在南海北部东沙海域的海上试验,试验结果的系统研究分析以及磁测和地震剖面两种手段的综合解释,成功地尝试了用高精度海洋磁测成果中的磁力总场和梯度变化特征来识别水合物勘探中高分辨率地震剖面上的泥底辟构造真伪的技术方法。 相似文献
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近岸多波束测量中的GPS-RTK差分技术及其受影响的因素 总被引:4,自引:0,他引:4
分析了近岸多波束测量中应用GPS-RTK差分技术对船只导航与定位,对在受波浪影响的多波束测量中,船只所受潮汐、换能器吃水的动态变化量等诸影响因素的改正以及船只的运动姿态纠正等问题进行了讨论。使用GPS-RTK系统可以有效地解决潮汐(水位)、波浪影响和换能器吃水的动态变化量对多波束测量精度综合影响的问题,如果使用"一加三"的GPS-RTK接收机,还可以实现船只姿态的高精度综合修正。同时,对4个影响GPS-RTK差分技术系统能力的主要因素应引起重视,采取措施加以解决,使近岸的多波束测量工作更加富有成效。 相似文献
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Chung-Hwa Park Ji-Hwan Byun Kyung-Sik Won Hyun-Tae Cho 《Marine Georesources & Geotechnology》2017,35(1):127-135
The alluvial deposits are highly heterogeneous and thus special techniques for investigating the subsurface have been required to obtain high quality data. The objective of this study is to apply two geophysical methods to alluvial deposits: a seismic survey method and the electrical resistivity method. The one-dimensional sounding method known as the standard penetration test is also applied to investigate subsurface properties and to compare these results with those measured by the geophysical methods. In seismic survey method, the seismic impulse source system shotgun is used to strongly propagate the elastic wave through the soil. The nonpolarizable electrode is selected to obtain the most reliable result by reducing the contact resistance. The application test is performed at Nakdong River in the southern part of Korean Peninsula where the area consists of alluvial deposits. The four profiles are selected for conducting the geophysical methods and the ranges of profiles are 115 ~ 205 m with interval distance of 5 m. The six one-dimensional soundings are performed in the intersection of geophysical profiles. Even though the measured results based on the geophysical method and one-dimensional sounding show slight difference, every result is applied to estimate subsurface characterization as the complementary data. 相似文献
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This article examines visitors’ normative acceptance of encounters with boats at a marine protected area and the extent that the number of boats, size of boats, and size of boat on which individuals were traveling influences these encounter norms. Data were obtained from a survey of 439 people visiting Molokini Shoal Marine Life Conservation District in Hawai’i, and photographs depicting four levels of boat use and three proportions of boat size measured encounter norms. Number of boats most strongly influenced encounter norms, boat size was less influential, and the size of boats on which respondents were traveling had little influence. Visitors wanted fewer boats at this site and a majority would not accept encountering more than 15 or 16 boats at one time. When the impact of boat size was considered, they would not accept encountering more than 12 large boats to 17 small boats. Implications for future research and managing standards of quality and social carrying capacity indicators at this marine protected area are discussed. 相似文献
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海洋高分辨率地震调查主要受震源系统、接收系统、缆源的调谐组合技术、地震记录系统和野外作业条件的影响。缆源的调谐组合技术是整个方法研究最为关键的环节之一。通过对“电缆、震源的沉放深度”等野外参数的合理组合,达到最理想的勘探效果。受地震勘探中“鬼波效应”的影响,缆源的调谐组合参数与地震系统的接收频率直接相关,对地震调查资料影响很大。文中从地震系统的滤波效应、直达波与鬼波传播路径及时间差及野外资料的处理对比和理论计算,分析了直达波和鬼波的综合效应,结果表明理论与实际资料在陷波点及幅频特性方面非常一致。研究结果在“海洋天然气水合物调查”项目中得到了应用,对缆源沉放深度的确定具有一定的指导意义。 相似文献