一种卫星钟差精度评估方法     

于合理  郝金明  刘伟平  田英国  廖琪 《海洋测绘》2014,(2):11-13

GNSS观测量测量的是测站与卫星间的相对时间延迟,卫星钟差求解的是相对于基准钟的相对钟差,因此卫星钟差的精度评估方法不同于其他GNSS产品。分析了卫星钟差的精度评估方法,采用消除卫星钟系统偏差的方法进行钟差精度的评估,得到的各产品的精度评定结果与各产品公布的钟差精度基本一致,证明了此方法的有效性。  相似文献   

一种动态参考站RTK模糊度解算方法     

喻国荣  刘经南  涂冰英  姚宜斌 《武汉大学学报(信息科学版)》2004,29(5):407-410

根据两空间的不同特性和两空间模糊度之间的匹配关系 ,提出了双空间搜索算法 ,使两空间的模糊度候选值明显减少 ,因此可以加快模糊度的搜索速度 ,并用车载试验数据验证了方法的正确性。车载“动对动”定位结果与常规RTK结果比较 ,精度达到mm级  相似文献   

强震仪器常用授时方式的优缺点及应用——以ETNA2为例     

何金刚  李文倩  魏斌 《内陆地震》2019,(2):137-142

地震观测仪器的计时单元是地震观测仪器不可或缺的组成部分,以强震动观测授时为例,将常用强震动观测仪器计时单元进行简要介绍,并对5种授时方式的原理及优缺点进行分析,根据强震动观测组网方式和布设条件的差异,采取不同的授时方式,以求在条件允许的范围内,为强震观测提供更佳的时间服务。  相似文献   

Evaluation of WaPOR V2 evapotranspiration products across Africa     

Megan L. Blatchford  Chris M. Mannaerts  Sammy M. Njuki  Hamideh Nouri  Yijian Zeng  Henk Pelgrum  Steven Wonink  Poolad Karimi 《水文研究》2020,34(15):3200-3221

The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open-access of remotely sensed derived data (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long-term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall correlation of 0.71, and a root mean square error of 1.2 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The relative soil moisture content (SMC), the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.  相似文献   

The representation of sediment source group tracer distributions in Monte Carlo uncertainty routines for fingerprinting: An analysis of accuracy and precision using data for four contrasting catchments     

Simon Pulley  Adrian L. Collins  J. Patrick Laceby 《水文研究》2020,34(11):2381-2400

Previous studies comparing sediment fingerprinting un-mixing models report large differences in their accuracy. The representation of tracer concentrations in source groups is perhaps the largest difference between published studies. However, the importance of decisions concerning the representation of tracer distributions has not been explored explicitly. Accordingly, potential sediment sources in four contrasting catchments were intensively sampled. Virtual sample mixtures were formed using between 10 and 100% of the retrieved samples to simulate sediment mobilization and delivery from subsections of each catchment. Source apportionment used models with a transformed multivariate normal distribution, normal distribution, 25th–75th percentile distribution and a distribution replicating the retrieved source samples. The accuracy and precision of model results were quantified and the reasons for differences were investigated. The 25th–75th percentile distribution produced the lowest mean inaccuracy (8.8%) and imprecision (8.5%), with the Sample Based distribution being next best (11.5%; 9.3%). The transformed multivariate (16.9%; 17.3%) and untransformed normal distributions (16.3%; 20.8%) performed poorly. When only a small proportion of the source samples formed the virtual mixtures, accuracy decreased with the 25th–75th percentile and Sample Based distributions so that when <20% of source samples were used, the actual mixture composition infrequently fell outside of the range of uncertainty shown in un-mixing model outputs. Poor performance was due to combined random Monte Carlo numbers generated for all tracers not being viable for the retrieved source samples. Trialling the use of a 25th–75th percentile distribution alongside alternatives may result in significant improvements in both accuracy and precision of fingerprinting estimates, evaluated using virtual mixtures. Caution should be exercised when using a normal type distribution, without exploration of alternatives, as un-mixing model performance may be unacceptably poor.  相似文献   

稀无控制点无人机遥感影像几何定位方法研究     

贺少帅  周乃恩  朱振宇 《地理信息世界》2019,(2):96-99

无人机以机动灵活、作业周期短和成本低等优势被广泛应用于基础测绘等领域。然而无人机航摄系统采集像片通过传统方法需要密集分布控制点,导致作业成本增加及生产效率下降影响经济效益。为此,在考虑到航测相机曝光延迟的基础上提出基于GPS辅助空中三角测量的稀无地面控制点的无人机遥感影像高精度几何定位方法,并通过实际测试生产数字线划图(DLG)和数字正射影像图(DOM),可满足1∶1000地形图测绘的技术要求,其高效率、低成本的生产模式较常规方法更具有推广意义,尤其是在西部测图以及岛礁测量人烟稀少人员很难或无法到达且使用常规测量方法无法满足成图要求的区域。  相似文献   

青海省卫星导航定位基准站网关键技术与性能测试     

马进全  赵利江  张生鹏 《地理信息世界》2019,26(2):126-130

在青海省卫星导航定位基准站网的建设过程中,遇到了土壤盐碱化以及无人区网络、电力供应困难和安全性不足的问题,尝试建设临时参考站以及企图依托通信铁塔建设参考站,最终通过结合卫星导航定位基准站和通信铁塔的建设特点和要求,设计建设了全新的青海省卫星导航定位基准站,从而解决了上述问题。其性能除满足现行规范要求外,同时具备成本低、环保性好、可自主状态监测和实时侦测的优点。  相似文献   

通过改进自适应PSO优化BP网络预测大坝变形     

刘忠豹 《大地测量与地球动力学》2019,39(5):528-532

提出自适应粒子群神经网络（ADPPSO-BP）算法,并加入自适应变异算子,提高粒子跳出局部搜索的能力,实现对坝体位移的精准预测。以丰满大坝为例进行验证,建立PSO-BP（粒子群神经网络）、LPSO-BP（线性粒子群神经网络）、改进ADPPSO-BP（改进自适应粒子群神经网络）3种模型,对大坝进行变形预测。结果表明,ADPPSO-BP预测误差最小。  相似文献   

Investigating spatial error structures in continuous raster data     

《International Journal of Applied Earth Observation and Geoinformation》2019

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多频率InSAR提取沼泽湿地DEM精度对比分析   总被引：1，自引：1，他引：0  

付波霖  耿仁方  李颖  高二涛  范冬林 《测绘通报》2019,(10):1-7

选取3种波长的干涉SAR数据对提取沼泽湿地区域的DEM,并随机从1：10 000地形图中选取111个点数据进行精度验证,最后对比分析了沼泽湿地植被对于不同SAR波长的干涉相干性差异。结果表明：L-band ALOS-1 PALSAR精细模式的HH单视复数数据与1：10 000地形图数据吻合度较好,76.58%的高程值差异在3 m以内,其相干系数比C-band Sentinel-1A IW模式的VV单视复数数据和X-band TerraSAR HH单视复数数据要高;更适合利用雷达干涉测量技术提取沼泽湿地的DEM;不同湿地植被类型的相干系数有较大差异,岛状林和灌草结合的湿地植被分布区相干系数值较大,而浅水沼泽植被区和深水沼泽植被区相对较低。  相似文献