共查询到18条相似文献,搜索用时 562 毫秒
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随着北斗卫星导航系统的建成与运行,目前已形成多系统导航定位的局面。基于短基线,首先对密林地区的GPS、BDS、GLONASS的卫星可见性以及伪距观测值的质量进行了简单的评价,然后分析了密林地区GPS、BDS、GLONASS单系统、双系统及三系统组合模式下单点定位及伪距差分定位性能。结果表明:在密林地区,GNSS多系统组合能够明显提高定位精度,GPS/BDS组合定位的精度优于GPS/GLONASS、BDS/GLONASS组合,而GPS/BDS/GLONASS的定位精度最高。 相似文献
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合理的观测值权阵能提高BDS、GPS及其组合系统伪距单点定位的精度。对比分析了各系统在实测数据和模拟观测条件下等权模型、高度角模型、Helmert方差分量模型3种随机模型的定位精度。结果表明:在模拟观测条件下, BDS/GPS组合系统精度最高,BDS系统次之,基于Helmert方差分量模型的精度最优,高度角模型次之;在正常观测条件下, BDS系统平面精度高于GPS系统,但高程精度低于GPS系统,其余结论与模拟条件下结果一致。研究结果可在提高BDS、GPS及其组合系统伪距单点定位精度方法中起参考作用。 相似文献
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基于多测站观测数据,采用伪距相位差组合和伪距多径组合方法,分析了GPS、Galileo、BDS和QZSS 4个系统伪距测量噪声和多径误差,比较了各系统内部信号数据质量以及系统间兼容信号数据质量。结果表明:GPS系统中L2C信号伪距测量精度要优于L2信号;Galileo系统中E5信号伪距测量精度最优,其E1和E5a信号伪距测量精度分别优于GPS/QZSS L1和L5信号;QZSS信号伪距测量精度与GPS信号基本一致;BDS系统三频信号伪距多径中均存在与高度角相关的系统性偏差,最大可达1m,且其三类卫星伪距测量精度有所差异,相同高度角条件下,GEO卫星伪距测量精度最优,IGSO卫星次之,MEO卫星最差。 相似文献
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分别采用非差无电离层组合模型与非差非组合模型进行批量静态定位解算,对比两者的定位精度以及ZPD估计精度。设计并实现两种模型的并行解算方法,提高非差模型的计算效率。大网数据实验结果表明,两种模型定位精度基本一致,非差非组合ENU的3个方向平均偏差为(4.2,2.8,6.6)mm,组合模型的平均偏差为(4.0,2.8,6.3)mm,但非差非组合模型的解算更加耗时,约是组合模型计算时间的1.4倍。多核环境下,两种模型的并行解算效率均比传统串行模型得到了提高。结果表明,双核并行和四核并行的计算效率比单核串行计算均分别提高了40%和60%以上。 相似文献
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The Indian Regional Navigation Satellite System (IRNSS) has recently (as of May 2016) become operational. The system has been developed with the objective of offering positioning, navigation, and timing (PNT) to users in its two service areas, covering the Indian landmass and the Indian Ocean, respectively. It is the goal of this contribution to provide further insight into the full-constellation L5 pseudorange single-point positioning (SPP) capabilities of the system. A detailed dilution of precision (DOP) analysis of its two service areas, including the identification, in location and time, of poor receiver-satellite geometries is provided. It is hereby demonstrated how the impact of some of these poor receiver-satellite geometries can be mitigated by means of height-constraining. An overview and analysis of the SPP precision is also provided including easy-to-use representative day-averaged values for a grid of locations covering the two service areas. 相似文献
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针对遥感影像数据大面积覆盖的特性,利用数学形态学提出了一种多目标海岛水边线的同步提取模型,模型包括:利用K-means算法的海岛区域粗分割;基于灰度膨胀算法的海岛初始轮廓曲线确立;利用水平集算法的海岛水边线优化。以福州海域的多目标海岛水边线提取为例,将本文模型与K-means模型、二值化高斯滤波水平集模型(SBGFRLS)和基于改进水平集的海岛边界快速分割模型(ILSM-IBRS)进行了比较。结果表明,本文模型弥补了K-means模型的过分割现象,其计算耗时较SBGFRLS和ILSM-IBRS模型分别节省了96.16%和86.96%;其迭代次数分别减少了97.07%和90.59%。由此可见,本文模型解决了现有提取模型效率低、过分割等现象,实现了多目标海岛水边线的同步提取,为海岛普查等提供了一种快速提取方法。 相似文献
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《Coastal Engineering》2006,53(1):93-98
The artificial compressibility method for solving the unsteady Navier–Stokes equations is discussed. Typically, this method is combined with a dual time stepping procedure which involves an iteration in pseudo-time within each physical time step, and which guarantees a convergence towards the solution for the incompressible flow problem. Numerous examples from the literature, however, ignore the pseudo-time iteration, in which case the choice of artificial compressibility becomes a tradeoff between accuracy and numerical efficiency. In this case it becomes important to establish thresholds for the artificial compressibility. In order to establish such thresholds, we derive linear wave solutions for progressive and standing waves under the influence of artificial compressibility. Thresholds are given in terms of the Mach number and the Courant number. 相似文献
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