Initial results of centralized autonomous orbit determination of the new-generation BDS satellites with inter-satellite link measurements   总被引：3，自引：0，他引：3  

Chengpan Tang  Xiaogong Hu  Shanshi Zhou  Li Liu  Junyang Pan  Liucheng Chen  Rui Guo  Lingfeng Zhu  Guangming Hu  Xiaojie Li  Feng He  Zhiqiao Chang 《Journal of Geodesy》2018,92(10):1155-1169

Autonomous orbit determination is the ability of navigation satellites to estimate the orbit parameters on-board using inter-satellite link (ISL) measurements. This study mainly focuses on data processing of the ISL measurements as a new measurement type and its application on the centralized autonomous orbit determination of the new-generation Beidou navigation satellite system satellites for the first time. The ISL measurements are dual one-way measurements that follow a time division multiple access (TDMA) structure. The ranging error of the ISL measurements is less than 0.25 ns. This paper proposes a derivation approach to the satellite clock offsets and the geometric distances from TDMA dual one-way measurements without a loss of accuracy. The derived clock offsets are used for time synchronization, and the derived geometry distances are used for autonomous orbit determination. The clock offsets from the ISL measurements are consistent with the L-band two-way satellite, and time–frequency transfer clock measurements and the detrended residuals vary within 0.5 ns. The centralized autonomous orbit determination is conducted in a batch mode on a ground-capable server for the feasibility study. Constant hardware delays are present in the geometric distances and become the largest source of error in the autonomous orbit determination. Therefore, the hardware delays are estimated simultaneously with the satellite orbits. To avoid uncertainties in the constellation orientation, a ground anchor station that “observes” the satellites with on-board ISL payloads is introduced into the orbit determination. The root-mean-square values of orbit determination residuals are within 10.0 cm, and the standard deviation of the estimated ISL hardware delays is within 0.2 ns. The accuracy of the autonomous orbits is evaluated by analysis of overlap comparison and the satellite laser ranging (SLR) residuals and is compared with the accuracy of the L-band orbits. The results indicate that the radial overlap differences between the autonomous orbits are less than 15.0 cm for the inclined geosynchronous orbit (IGSO) satellites and less than 10.0 cm for the MEO satellites. The SLR residuals are approximately 15.0 cm for the IGSO satellites and approximately 10.0 cm for the MEO satellites, representing an improvement over the L-band orbits.  相似文献   

基于样条函数的海岸带变化监测影像局部配准优势分析     

许会芳  孙畅  郑丹 《测绘与空间地理信息》2018,(5):168-169

海岸带变化监测以遥感影像为矢量更新依据。在实际应用中,由于数据源复杂,全色影像与底图套合、多光谱影像与全色配准容易出现局部超限,为项目生产带来一定的难度。本文主要介绍利用样条函数进行影像的局部配准以满足项目精度要求。  相似文献   

基于PixelGrid的标准时点核准影像单景几何纠正方法研究     

王菲菲  孙畅  袁如金 《测绘与空间地理信息》2018,(8):146-148

地理国情普查是国务院部署的重大项目,其中,第一次全国地理国情普查标准时点核准工作于2015年正式启动。面对多源的卫星遥感数据,对于影响因素复杂区域很难实现影像的自动纠正,因而,本文主要介绍了利用PixelGrid软件进行单景影像几何纠正的方法,为其他项目的困难区域影像处理提供参考。  相似文献   

Comparative analysis of significant wave height between a new Southern Ocean buoy and satellite altimeter          下载免费PDF全文

Jianjun Kang  Runyu Mao  Yiting Chang  Hongli Fu 《大气和海洋科学快报》2021,14(5):49-55

中国于2019年第35次南极考察中,首次在南大洋布放了锚系实时综合观测浮标(西风带海洋环境监测浮标,WEMB),为深入了解此海区的海洋环境变化提供了宝贵资料.国家海洋技术中心WEMB研究团队基于AVISO公开发布的多颗卫星高度计L3产品,通过数据配对,误差统计和最小二乘线性拟合等方法,对西风带海洋环境监测浮标的有效波高数据误差进行了分析与校正.校正后的浮标有效波高统计显示西风带常年处于大浪以上海况,观测期间内57％处于巨浪海况,并且伴随有高度相关的大风天气.  相似文献   

NDVI dynamic changes and their relationship with meteorological factors and soil moisture   总被引：1，自引：0，他引：1  

Hongxue Zhang  Jianxia Chang  Lianpeng Zhang  Yimin Wang  Yunyun Li  Xiaoyu Wang 《Environmental Earth Sciences》2018,77(16):582

Normalized difference vegetation index (NDVI) is an important indicator for measuring vegetation coverage, which is of great significance for evaluating vegetation dynamics and vegetation restoration. It can clearly analyze the suitable growth condition of vegetation by studying the relationship between meteorological factors, soil moisture and NDVI. Based on MODIS/NDVI data, the spatio-temporal characteristics of vegetation coverage in the Weihe River Basin (WRB) were analyzed by the trend analysis method. The relationship of NDVI with meteorological factors and NDVI with soil moisture simulated by the soil and water assessment tool (SWAT) model was analyzed in this paper. The results show that NDVI values gradually change with an increase from north to south in the WRB. The maximum of the average monthly NDVI is 0.702 (August) and the minimum is 0.288 in February from 2000 to 2015. The results of the seven grades of NDVI trend line slope indicate that the improvement area of vegetation coverage accounts for 30.93% of the total basin, and the degradation area and basically unchanged area account for 23% and 42.9%, respectively. The annual mean soil moisture is 19.37% in the WRB. There was a strong correlation between NDVI and precipitation, temperature, evaporation and soil moisture, and the correlation coefficients were 0.78, 0.89, 0.71 and 0.65, respectively. The ranges of the most suitable growth conditions for vegetation are 80–145 mm (precipitation), 13–23 °C (temperature), 94–144 mm (evaporation) and 25–33% (soil moisture), respectively.  相似文献   

Effect of climate change on water resources in the Yuanshui River Basin: a SWAT model assessment     

Yingdong Yu  Jiahong Liu  Zhiyong Yang  Yongqiang Cao  Jing Chang  Chao Mei 《Arabian Journal of Geosciences》2018,11(11):270

The Yuanshui River Basin is one of the most important river basins ensuring food production and livelihoods in the Hunan and Guizhou Provinces of China. Based on digital elevation model, land use, soil, and meteorological data, the soil and water assessment tool was used to analyze the response of water resources in the basin to climate change. Specifically, the monthly runoff from the Yuanshui River Basin was simulated. Runoff measurements from the 1961–1990 series were used to calibrate model parameters, and measurements from the 1991–2010 series were used for model validation. The Nash–Sutcliffe efficiency coefficient, correlation coefficient, and water balance error were used to evaluate the simulation results; the values obtained for these parameters were 0.925, 0.929, and 2.0%, respectively, indicating that the established model can be applied successfully to runoff simulations. To evaluate the effects of climate change and human activities on runoff, 24 different climate scenarios were modeled. By comparing the model simulation results with the baseline scenario, the effects of climate change were analyzed by year, during the dry season, and during extremely dry conditions. The results showed that runoff decreased with increasing air temperature and decreasing precipitation, and that the effects of rainfall on runoff were greater than those of air temperature. Under the same baseline conditions, the effects of climate change on runoff were most pronounced during extremely dry months.  相似文献   

Geotechnical design parameter evaluation using the alluvial plain characteristics in southeastern Iraq     

Jinung Do  Ong Heo  Yeo-Won Yoon  Ilhan Chang 《Arabian Journal of Geosciences》2018,11(20):647

Geotechnical construction is responsible for the overall stability of superstructures, and if there are design errors, the structure will be exposed to potential problems. Geotechnical design starts with the correct interpretation of the target ground. Southeastern Iraq is mainly comprised of an alluvial plain with diverse geological features, and, therefore, geotechnical design requires a detailed interpretation and understanding of the area. This paper reports on laboratory and field tests and in-depth analyses conducted on these alluvial plains. The results reveal that the upper layer of this area is highly over-consolidated. This may have been caused by the removal of overburden pressure as a result of glaciation and desiccation. The highly over-consolidated soils caused considerable sample disturbance by swelling the bored sample; this provided less reliable results. However, the cone penetration test was regarded as the most appropriate field assessment method for deriving sensible geotechnical design parameters. Despite its limitations in clayey soils, the standard penetration test provided results that matched well with previous observations due to the high penetration resistance of the highly over-consolidated ground. Down-hole tests and plate load tests were considered less reliable methods due to their limited applicability in this area. This study considers geographical features, laboratory methods, and empirical correlations from in situ tests, and, therefore, provides a well-summarized guideline to evaluate special geotechnical characteristics of the alluvial plain in southeastern Iraq.  相似文献   

Hydro-thermal coupled analysis for health monitoring of embankment dams     

Tewodros Y. Yosef  Chung R. Song  Ki-Tae Chang 《Acta Geotechnica》2018,13(2):447-455

Measuring and analyzing internal dam temperature may provide insight into evaluating the integrity of earthen dams. Temperature in a dam, with the advent of modern distributed temperature sensing (DTS) technique, is conveniently measured. The analysis of the temperature is conducted based on a hydro-thermal coupled analysis technique. In this study, DTS-based temperature data and VS2DHI (a finite difference code for analyzing two-dimensional heat transport in porous media) were used to analyze the hydro-thermal coupled behavior in a dam. The results of this analysis show that the temperature variation in an earthen dam is closely related to seepage conditions. Additionally, a localized high-temperature (26 °C) zone found in the measured data of the dam, which raised concern to engineers on site, is explained through either hot water infiltration into the foundation layer or lower permeability of the foundation layer than the magnitude that appeared in the design document. These findings demonstrate that hydro-thermal coupled analysis has the potential for evaluating the integrity of earthen dams.  相似文献   

单多普勒雷达反演涡旋风场方法分析     

常亚楠  戴建华  黄兴友  郑石 《气象科技》2019,47(5):719-730

由于单雷达在探测台风临近、登陆时仍具有双部或多部雷达难以具备的优势,目前利用单多普勒雷达反演涡旋风场的方法并不多见,本文对能够反演涡旋风场的3种方法NIVAP(自然坐标系的积分VAP方法)、EVAPTC(反演热带气旋的EVAP方法)、GBVTD(地基速度追踪法)进行了比较,分别从每种方法的假设条件和数学方法以及结果精度来比较3种方法对涡旋风场的适用性。利用中尺度气旋Rankine模式模拟了纯涡旋性气旋、只有环境风场时、环境风场和辐合(辐散)同时存在时的径向速度场及风场,比较了各种情况下的反演风场和模拟风场的相似系数。在对模拟风场比较之后,选取了2014年"威马逊"台风登陆前1h、登陆时及登陆后1h的3个实测雷达资料,对比分析了3种方法反演实测资料的风场特征,3种方法中EVAPTC方法最好,GBVTD方法在应用中有一定的限制,NIVAP方法较差。  相似文献   

丹阳天王寺边坡稳定性评价及防治措施     

余成  葛伟亚  常晓军 《江苏地质》2018,42(2):345-348

针对苏南地区典型露采边坡的地层岩性及地质构造特点,以极限平衡理论为基础,运用GeoStudio软件中的SLOPE/W模块和VADOSE/W模块计算分析江苏丹阳天王寺边坡在天然工况、暴雨工况及地震工况下的稳定性。结果表明:天然工况下,潜在滑动面分布范围最小,稳定性最高,存在滑动的危险性;暴雨工况下,潜在滑动面分布范围有所增大,稳定性降低,边坡滑动的可能性较大;地震工况下,潜在滑动面分布范围最广,稳定性最低,边坡滑动的可能性很大。基于上述结果,提出防治措施。  相似文献