Characterization of spatial and temporal variation of suspended sediments in the Yellow and East China Seas using satellite ocean color data

Total suspended sediment (TSS) data concentrations are retrieved from two sets of satellite ocean color data (the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua and the Korean Geostationary Ocean Color Imager (GOCI)) using an existing regional model to characterize spatial and temporal variation of TSS in the Yellow and East China Seas. MODIS-derived TSS maps show that TSS concentrations are, in general, high along the Korean and Chinese coasts including the Bohai Sea and the Yangtz River estuary, and lower in the middle of the Yellow Sea and the southeastern area of the East China Sea. The monthly average of 10-year MODIS data reveals that TSS values are highest during winter (January to February) and lowest in summer (July to August). Short-term TSS concentrations retrieved from GOCI data showed the dominant influence of semi-diurnal tidal changes on sediment dynamics through temporal (hourly) and spatial distribution in coastal zones of the Yellow sea. The results presented here demonstrate that the satellite-derived TSS products can be utilized as an application tool for future studies on long- and short-term sediment dynamics of turbid coastal waters. In particular, GOCI observations provide unique important capabilities to characterize and quantify the water properties at high temporal (hourly) and spatial (0.5 km) resolutions in the turbid coastal waters of the Yellow Sea and its vicinities.     

北极海域SAR海浪方向谱反演及其与中法海洋卫星CFOSAT/SWIM数据的比较

The interaction between ocean waves and sea ice in the Arctic ocean has received significant attention. However, the study on this issue is significantly limited due to the lack of observation data. Synthetic Aperture Radar (SAR) plays an important role in the research of ocean wave and sea-ice interaction because of its unique capability of imaging sea surface in two dimensions. Sentinel-1 (S1), which consists of Sentinel-1A (S1A) and Sentine-1B (S1B), can cover the entire Arctic Area within 2 days. The Interferometric Wide Swath (IW) mode, one of the main imaging modes of S1 in the Arctic, has been providing SAR images with a high resolution of 10 m. The ocean wave spectra are derived using the S1 IW data. The spectra are likely to provide vital observation for studying the interaction between sea-ice and waves as they present the distribution of wave energy and their variations in different frequencies and directions. Meanwhile, the retrieved ocean wave spectra are an excellent validation data source for SWIM, which is onboard the China-France Oceanography Satellite and provides measurements of ocean wave spectra in the global ocean.In this study, we use the sub-images from the S1 IW image with a size of 1024 pixels × 1024 pixels (10.24 km × 10.24 km) to retrieve ocean wave spectra by using a nonlinear retrieval method (i.e., MPI scheme). The retrieved ocean wave spectra and wave parameters are compared with SWIM measurements acquired at an incidence angle of 10°, and the Significant Wave Height (SWH) is measured at nadir. The SWIM spectrum covers a large area by approximately 70 km × 90 km. To make a comparison, all the SAR sub-image spectra within a SWIM beam coverage are averaged to calculate a new observed SAR spectrum, which is inputted into the MPI inversion scheme. Then, the retrieved SAR ocean wave spectrum is compared with the SWIM spectrum. The footprint size of the SWIM nadir beam is 18 km, which is comparable to the S1 sub-image size. Accordingly, a SAR sub-image is extracted at SWIM nadir, and the corresponding ocean wave spectrum is retrieved. The SWH is calculated by integrating the retrieved wave spectra to compare with the SWIM nadir measurements of SWH. The experiment was carried out using the data acquired in September 2020 in the Greenland Sea and Norwegian Sea, where the ocean waves generated in the North Atlantic and propagating vast distances to the ice-covered area in the Arctic ocean can be frequently observed. Fifty-four ocean wave spectra were retrieved from 25 IW data and are compared with the SWIM slope spectra. The comparison shows that the SAR-retrieved spectra are consistent with SWIM spectra in terms of structure and energy distribution. Good agreements are also found between the integral parameters of the SAR ocean wave spectra and SWIM slope spectra. The comparison yields a bias and an RMSE of 0.11 and 0.71 m for SWH and a bias and an RMSE of -0.52 s and 0.62 s for mean wave period. The comparison of the dominant wave parameters yield a bias of -7.74° and an RMSE of 15.75° for the dominant wave direction and a bias of -0.56 m and an RMSE of 52.73 m for the dominant wavelength. Furthermore, 5075 data pairs of S1-retrieved SWH and SWIM nadir SWH were collocated and compared. The comparison result yields a bias of 0.03 m, an RMSE of 0.48 m, and a correlation of 0.95. The comparison between the S1 retrieved results and the SWIM measurements suggests that ocean wave information can be effectively retrieved from S1 IW data by using the MPI method in the Arctic ocean. Although the MPI method relies on prior information, it is still an effective method for obtaining ocean wave spectra in high resolution. The spectra retrieved from S1 are likely to show the energy attenuation of ocean waves in different frequencies and directions when propagating toward an ice-covered area. This finding will be of great support for the further study on the interaction between sea ice and ocean waves. © 2023 National Remote Sensing Bulletin. All rights reserved.     

地磁测量中日变观测的常见问题

地磁日变观测质量主要与仪器性能和观测点的环境有关。本文重点研究了目前在地磁日变测量中主要采用的HC90D氦光泵磁力仪的信号失锁问题,日变站的选址二个对于最终观测精度影响很大的问题,并提出了具体的解决方法。     

大阳山隧道控制网布设

隧道工程以所处地形地质结构复杂、劳动强度大及后期维护问题多而著称。高海拔地区隧道受地质气候条件影响,其测量及施工难度较大,对高速铁路隧道而言,更是如此。本文以大阳山隧道为例,结合GPS测量技术特点对该隧道控制网布设进行了设计,得出了相关结论。     

基于等角比例投影的球面三角四叉树剖分模型

将人不可及的观测统称为遥感,使地面传感器成为遥感的一部分.提出遥感科学与技术的基本内容,包括传感器研制、遥感数据获取、数据处理、信息提取和应用5个部分.其理论基础是辐射传输过程模拟与反演,贯穿于各个组成部分.数据的可视化及传输发布存在于从数据获取到应用的各个环节.遥感科学与技术正处于快速发展时期,各个方面都有前沿问题.辐射传输理论中的尺度和多角度问题,地形对辐射和图像几何影响及相应的多源多时相数据的匹配问题,遥感信息提取中自动化和目视解译的结合以及信息提取新策略问题,遥感与基于过程模拟的气候一水文-生态模式相结合的四维数据同化技术等是当前遥感科学与技术发展中的重要学科前沿.四维数据同化技术是突破遥感瞬时信息获取、实现图像与机理模型有机结合、改善自身数据产品质量和促进地学大范围模拟准确性的重要发展方向,能增强遥感对全球变化科学的贡献.     

嫦娥一号IIM数据应用处理流程分析

对嫦娥一号干涉成像光谱仪（IIM）数据的特点进行了分析,并就存在的一些问题提出了解决方案,制定了IIM数据应用处理流程,为该数据的正确使用提供方法参考。研究结果表明,在空间域传感器左侧响应偏低,右侧响应偏高;在波谱域长波段响应存在较大偏差。经过绝对定标和辐射畸变校正后的反射率与地基望远镜光谱匹配良好,可以用于应用研究。利用校正后的数据对Aristarchus地区岩石类型开展初步研究的结果表明,该地区在纵向和横向上都存在岩性的多样性。校正后的图像不仅提高了分类精度,还被识别出撞击坑可能存在的滑坡。嫦娥一号IIM能够在全球、区域和局部尺度上以较高的空间分辨率和光谱分辨率获取月表元素和矿物成分信息,有助于深化对月球形成和演化的认识。     

引黄入晋工程的桩号系统设计与应用

对于象引黄入晋工程这样的由多个混凝土建筑物紧密且“硬性”衔接而成的,高精度、超长线路工程来说,村号系统设计是一个十分重要且具有实际应用意义的问题,为了避免高斯投影误差与高程投影误差对桩号的影响,解决桩号方面由此而引起的矛盾,以及满足工程远程运营管理对桩号的要求,作者提出了在工程的勘测设计、施工和运营管理等阶段中,应分别使用设计桩号、施工桩号和管理桩号,这３种桩号就构成了超长线路工程的桩号系统。文中     

定位参数抗差估计的无偏性

根据抗差估计中误差的最基本假设一对称分布,考虑到ρ函数的条件及把反对称估计作为抗差估计计算迭代的初始值,验证了定位参数的抗差估计值也一定是反对称估计,满足无偏性条件,得到定位参数的抗差估计是无偏估计.     

基于物联网/RS集成的环境监测研究

提出一种利用物联网的无线传感器网络技术辅助遥感解译的环境监测方法。该方法通过集成无线传感器网络技术和卫星遥感技术,充分发挥无线传感器网络获取局部地面信息翔实性和遥感技术大面积获取环境信息方便性的优势互补,为环境监测以及环境保护提供数据决策支持。文章着重探讨了基于Zigbee的无线传感器网络与远距离的GPRS结合实现远程辅助遥感解译的环境监测方法,具有广阔的应用前景。     

GPS精密定位中的海潮位移改正

根据海洋负荷潮理论，利用NAO99b全球海潮模型，计算了中国部分IGS站的海潮位移改正，并将海潮位移改正应用到GPS数据处理当中。在GAMIT软件的解算过程中，分别按加入和不加入海潮位移改正，对GPS基线分量和测站坐标分别进行了计算和比较分析。结果表明，海潮位移改正无论是对GPS基线分量还是对测站坐标，都有一定的影响。