Collaborative validation of GlobeLand30:Methodology and practices     

Jun Chen  Lijun Chen  Fei Chen  Yifang Ban  Songnian Li  Gang Han  Xiaohua Tong  Chuang Liu  Vanya Stamenova  Stefan Stamenov 《地球空间信息科学学报》2021,24(1):134-144

30-m Global Land Cover(GLC)data products permit the detection of land cover changes at the scale of most human land activities,and are therefore used as fundamental information for sustainable development,environmental change studies,and many other societal benefit areas.In the past few years,increasing efforts have been devoted to the accuracy assessment of GlobeLand30 and other finer-resolution GLC data products.However,most of them were conducted either within a limited percentage of map sheets selected from a global scale or in some individual countries(areas),and there are still many areas where the uncertainty of 30-m resolution GLC data products remains to be validated and documented.In order to promote a comprehensive and collaborative validation of 30-m GLC data products,the GEO Global Land Cover Community Activity had organized a project from 2015 to 2017,to examine and explore its major problems,including the lack of international agreed validation guidelines and on-line tools for facilitating collaborative validation activities.With the joint effort of experts and users from 30 GEO member countries or participating organizations,a technical specification for 30-m GLC validation was developed based on the findings and experiences.An on-line validation tool,GLCVal,was developed by integrating land cover validation procedures with the service computing technologies.About 20 countries(regions)have completed the accuracy assess-ment of GlobeLand30 for their territories with the guidance of the technical specification and the support of GLCVal.  相似文献   

测站坐标阶跃对参考框架稳定性的影响分析     

马一方  周晓慧  华培学 《测绘科学》2021,46(10):20-24

针对全球卫星导航系统(GNSS)测站坐标阶跃对参考框架稳定性的影响量级尚不明确的问题,该文选取了 340个全球分布的国际GNSS服务(IGS)测站建立长期GNSS参考框架.其中,测站运动模型包含线性速度、周年信号以及震后形变改正.通过迭代增加阶跃的数量,定量分析了测站坐标阶跃对建立的GNSS参考框架稳定性、测站速度及周年振幅的影响.结果表明,340个IGS测站坐标时间序列中存在的阶跃对建立的GNSS参考框架稳定性、测站水平方向速度以及测站周年振幅的影响量级均小于其精度,但是对测站垂直方向速度的影响较为显著.  相似文献   

A Simplified Calculation Method for Ultimate Mining Dimension in Thin Coal Seam     

Ban  Yuxin  Fu  Xiang  Xie  Qiang  Cui  Jianfeng  Xu  Hong 《Geotechnical and Geological Engineering》2021,39(5):3655-3667

Geotechnical and Geological Engineering - Coal seam mining is one of the most widely participated engineering activities in China. This study examined the failure process induced by underground...  相似文献   

DEM数据源及分辨率对HEC-HMS水文模拟的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

高玉芳  陈耀登  蒋义芳  彭涛 《水科学进展》2015,26(5):624-630

DEM数据源及分辨率会影响流域特征参数的提取,进而影响水文模拟结果.将ASTER 30 m DEM、SRTM 90 m DEM及基于ASTER 30 m DEM的40 m、50 m、60 m、70 m、80 m、90 m重采样DEM作为HEC-geoHMS模型输入,提取流域特征,采用HEC-HMS模型,以西笤溪流域为研究区域,分析2011年6月和2011年8—9月的两场降雨径流过程中,DEM数据源和分辨率对水文模拟输出的影响.研究结果表明,两次径流模拟结果与实测数据拟合都较好,模型确定性系数都大于0.82,但是单峰的洪水模拟效果总体更好,基于SRTM 90 m的模型确定性系数比基于ASTER 30 m DEM、重采样90 m DEM的模型确定性系数都大.基于重采样DEM的模型确定性系数变化较大,而且与分辨率的变化呈非线性关系.在HEC-HMS的模拟中,基于ASTER 30 m DEM和基于SRTM 90 m DEM的模拟输出结果相对误差相差3%~5%,基于SRTM 90 m DEM和基于重采样90 m DEM的模拟输出结果相对误差相差2%~4%,基于重采样DEM的模拟输出结果相对误差相差最大达到了11%.  相似文献   

多普勒天气雷达1 h降水产品的质量评估   总被引：2，自引：1，他引：1  

李晶  包云轩  蒋义芳  高玉芳  于鑫 《气象科学》2015,35(3):340-345

为评估多普勒天气雷达1 h降水量(OHP)产品在降水预报中的质量, 从南通新一代多普勒天气雷达的体扫资料及其覆盖范围内太湖流域34个雨量站的同期逐小时降水资料中选取了19个降水个例。以空报率、漏报率、准确预报临界指数、平均误差、平均绝对误差和均方根误差等, 为评估降水预报质量的指标。根据雨量站实测日降水量(P)和1 h降水量(P₁)大小分级, 对不同情况下的OHP进行质量评估。结果表明:(1)OHP的空报率和漏报率较高, 导致整体的准确预报临界指数偏低。(2)与不同的P和P₁量级相对应, 不同的OHP预报质量有明显差异。除P<10 mm时和P₁<1 mm时稍有高估外, 其他量级都存在低估, 且随着P的增加, 空报率和漏报率都减小。(3)对2007年9月18日的降水个例分析表明:OHP与实测的落区基本一致, 但降水强度上有偏差。不同站点的雨强偏差不同, 距南通雷达站100 km左右的OHP误差较小。  相似文献   

水位变化对鄱阳湖苦草潜在生境面积的影响          下载免费PDF全文

陈炼钢  陈黎明  徐祎凡  栾震宇  金秋  施勇  胡腾飞 《水科学进展》2020,31(3):377-384

苦草是鄱阳湖越冬水鸟的重要食物资源,为量化水位变化对鄱阳湖苦草生境的影响,基于环境流体动力学模型(EFDC)和生境适宜度曲线,构建了鄱阳湖苦草生境数值模拟模型;对三峡水库175 m试验性蓄水后鄱阳湖苦草潜在生境面积变化进行了连续模拟,建立了苦草潜在适宜生境和水深≤4 m水域面积变化与星子站水位的定量响应函数;并据此分析了三峡水库运用及拟建鄱阳湖水利枢纽对苦草潜在生境面积的影响。星子站水位15 m左右时苦草潜在生境面积最大,潜在适宜生境和水深≤4 m水域面积分别为1 703 km^2和2 336 km^2。三峡水库运用可有效保障鄱阳湖苦草潜在生境面积,但其扰动幅度也明显减小,潜在适宜生境和水深≤4 m水域面积序列标准差在三峡运用后减幅分别达到27%和47%。拟建鄱阳湖水利枢纽调控水位在其下闸蓄水期和长江上游水库蓄水调节期内宜分别控制在16 m以下和13.5 m以上,可保障潜在适宜生境及水深≤4 m水域面积与最大值相比减幅分别控制在20%和10%以内。成果明晰了水位变化对鄱阳湖苦草潜在生境面积的定量影响规律,为江湖新水沙条件下鄱阳湖生态系统保育提供了量化依据。  相似文献   

Analysis of ionospheric vertical total electron content before the 1 April 2014 Mw 8.2 Chile earthquake     

Weiping Jiang  Yifang Ma  Xiaohui Zhou  Zhao Li  Xiangdong An  Kaihua Wang 《Journal of Seismology》2017,21(6):1599-1612

This paper studies ionospheric vertical total electron content (VTEC) variations before the 1 April 2014 Mw 8.2 Chile earthquake. VTEC derived from 14 global positioning system (GPS) stations and global ionospheric map (GIM) were used to analyze ionospheric variations before the earthquake using the sliding interquartile range method, and the results showed that significant positive VTEC anomalies occurred on 28 March. To explore possible causes of these anomalies, effects of solar and geomagnetic activities were examined, and VTEC variations during 17 March to 31 March in 2009–2013 were cross-compared. Also, VTEC for a full year before the earthquake was investigated. The results indicated that the anomalies were weakly associated with high solar activities and geomagnetic storms and that the anomalies were not normal seasonal and diurnal variations. An analysis of the spatial distribution of the observed anomalies was also presented, and it demonstrated that the anomalies specifically appeared around the epicenter on 28 March. We suggest that the observed anomalies may be associated with the subsequent Chile earthquake. Equatorial anomaly variations were analyzed to discuss the possible physical mechanism, and results showed that the equatorial anomaly unusually increased on 28 March, which indicates that anomalous electric fields generated in the earthquake preparation area and the meridional wind are possible causes of the observed ionospheric anomalies.  相似文献   

"海鳐"波浪滑翔器研究进展及发展思路          下载免费PDF全文

田应元  吴小涛  王海军  熊童满  王华明  班伟  吴文辉 《数字海洋与水下攻防》2020,3(2):111-122

波浪滑翔器是一种能够完全借助自然能源长周期运行的小型水面无人航行器,具有超强的续航能力和一定的控位能力,能够执行长时间、大范围、持续的海洋环境观测,水面水下目标探测,跨域通信及信息传递等任务。在国家“863 计划”和国家重点研发计划等领域项目的支持下,中国船舶重工集团有限公司第七一〇研究所研制的“海鳐”波浪滑翔器在平台技术及应用研究上均取得了重要的进展,整体技术水平处于国内领先、世界先进,为在我国军事、海洋环境监测、海洋资源开发利用等领域的应用推广奠定了坚实的平台基础。同时,波浪滑翔器仍是一种有限能力的小型无人航行器,在实际应用中还有许多需要完善和提高的地方。介绍了“海鳐”波浪滑翔器的最新研制进展,总结了研制过程中的部分关键技术,并根据波浪滑翔器在实际应用中存在的一些问题对其技术的发展方向进行了初步探讨。  相似文献   

Optimal subreflector position determination of shaped dual-reflector antennas based on the parameters iteration approach     

Bin-Bin Xiang  Cong-Si Wang  Pei-Yuan Lian  Na Wang  You Ban 《天文和天体物理学研究(英文版)》2019,(4):151-160

A new method based on the parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas, that are distorted by gravity, to improve their electromagnetic(EM) performance. Both the features of shaped surface and the relationship between optical path difference(OPD) and far field beam pattern are employed. By describing the shaped dualreflector surface as a standard discrete parabola set, we can utilize the optical features of the standard Cassegrain system in the classical OPD relationship. Then, the actual far field beam pattern is expressed as the synthesis of ideal beam and error beam by decomposing subreflector adjustment parameters using a mechanical-electromagnetic-field-coupling-model(MEFCM). Furthermore, a numerical method for determining optimal subreflector position is presented. The proposed method is based on the iteration technique of subreflector adjustment parameters, and the optimal far field pattern is used for the iteration. The numerical solution of optimal adjustment parameters can be obtained rapidly. Results for a 25 m shaped Cassegrain antenna demonstrate that the adjustment of the subreflector to the optimal position as determined by the proposed method can improve the EM performance effectively.  相似文献   

0808号台风凤凰前部龙卷的环境场和雷达回波分析   总被引：5，自引：0，他引：5  

蒋义芳  吴海英  沈树勤  刘安宁 《气象》2009,35(4):68-75

用多普勒天气雷达、常规观测和地面加密观测资料对2008年7月29-30日发生在江苏的台风凤凰前部系列龙卷过程进行了详细分析.结果如下:该龙卷发生在台风前部风切变区里,低空较强的垂直风切变、极不稳定的大气层结和深厚的正涡度区,为龙卷的发生提供了热力和动力条件.龙卷回波的反射率因子特征表现为最大反射率因子梯度位于回波的后侧,一般都有弱回波区和后侧入流缺口相伴随.东台龙卷产生于飑线型弓形回波的顶点,具有相对较大的反气旋性切变.高邮龙卷中低层具有弱的气旋性涡旋,宝应龙卷回波的内部环流特征明显,有明显的中气旋结构.在业务工作中,强回波质心高度和垂直累积液态含水量的骤降、径向速度风场中气旋性涡旋的迅速发展是对龙卷的提前警戒很好的参考指标.  相似文献