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91.
Shengyue Ji Wu Chen Duojie Weng Zhenjie Wang Xiaoli Ding 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
This research is aiming for cycle slip detection and correction in case of ionospheric scintillation. Different from the normally discussed situation without ionospheric scintillation, ionospheric delay cannot be neglected due to abrupt ionosphere change. In this case, ionosphere-free testing quantities for cycle slip detection and correction have to be used. 相似文献
92.
前视合成孔径雷达(SAR)存在左右模糊问题,在直线航迹下,目标关于航线对称模糊,模糊关系不随航线变化,可利用波束形成进行全孔径解模糊处理;但在曲线航迹下,目标的模糊关系具有空变性,不能全孔径解模糊成像。针对这一问题,分析了曲线航迹下目标模糊关系的空变特性,提出一种前视多通道SAR快速后向投影子孔径处理解模糊成像算法。首先进行子孔径划分,在每个子孔径内目标的模糊关系近似不变,每个子孔径分别成像,然后通过波束形成对每幅子图像进行解模糊处理,最后融合子图像得到最终的成像结果。算法有效解决了曲线轨迹下目标模糊关系的空变性对解模糊的影响,仿真实验验证了算法的有效性。 相似文献
93.
T. Hobiger M. SekidoY. Koyama T. Kondo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Next-generation Very Long Baseline Interferometry (VLBI) system designs are aiming at 1 mm global position accuracy. In order to achieve this, it is not only necessary to deploy improved VLBI systems, but also to develop analysis strategies that take full advantage of the observations taken. Since the new systems are expected to incorporate four independent radio frequency bands, it should be feasible to resolve phase ambiguities directly from post-correlation data, providing roughly an order of magnitude improvement in precision of the delay observable. As the unknown ambiguities are of integer nature, it is discussed here how they the can be resolved analytically using algorithms which have been developed for Global Navigation Satellite System (GNSS) applications. Furthermore, it will be shown that ionosphere contribution and source structure effects, so-called core-shifts, can be solved simultaneously with the delay, which is the main geodetic observable for follow-on analysis. In order to verify the proposed algorithm, simulated observations were created using parameters from actual design studies. It is shown that, even in the case of low signal-to-noise ratio observations, reliable phase ambiguity resolution can be achieved and it is discussed how the integer ambiguity recovery depends on the number of observations and signal-to-noise ratio. 相似文献
94.
介绍了纤维缠绕金属内衬压力容器的工艺特点、性能优势和爆破前先泄漏(LBB)的安全失效模式,以及一般设计原则、构形、材料和工艺要求。分析了金属内衬的厚度、过渡区、焊接区和纤维缠绕层。以及输入输出极孔的设计技术。阐明了用于静力分析的解析法和数值法,以及用于循环寿命预测的断裂力学分析法。最后概述了一些新技术、新材料的应用情况,并指出了压力容器设计的发展趋势。 相似文献
95.
由于北斗定位系统的两颗卫星位于赤道的同步轨道,对地静止且可观测的载波相位信息少,因此传统多星系统求解整周模糊度进行定向的方法难以直接利用。针对此情况,利用延长基线可改变卫星-天线几何关系的方法,求解载波相位的整周模糊度,化不利为有利,实现双星的快速定向。针对基线在不同区域不同姿态下的仿真表明:当测试条件为基线原长1.5m,延长倍数为4时,载波相位测量精度为1%周,可实现优于0.1。的方位精度和0.05。的俯仰精度,如果延长基线或增加延长倍数,还可取得更高精度,证实了该方法的可行性和高精度性。同时由于该方法的基线安装机构简单可靠,使用时便于展开,因此可应用于环境复杂的快速定向场合。 相似文献
96.
Blewitt周跳探测方法的改进 总被引:2,自引:0,他引:2
在精密单点定位中,能否准确可靠地探测载波相位观测量中出现的周跳,直接影响到定位的精度及可靠性。本文概述了Blewitt周跳探测方法的基础原理,并对周跳的探测算法进行了改进,将电离层残差组合观测量一次差的变化是否超限作为周跳存在与否的判断依据。最后利用一段人为加入了几个典型周跳组合的双频观测数据进行验证,结果表明,改进后的算法能准确探测出两个载波上大于1周的任意周跳,提高了周跳探测的准确性。 相似文献
97.
98.
本文针对航空重力测量中利用单基准站差分GNSS方法估计载体加速度的局限性,提出了两种基于PPP的载体加速度高精度估计方法—位置差分法和相位差分法。在详细推导了两种估计方法解算方程的基础上,研究总结了方法各自的特点与优势,最后通过实验分析了卫星导航误差源对两种方法的影响。实验研究表明,相位差分法在抑制低阶误差方面更具优势;-2~+2周的整周模糊度解算偏差对位置差分法的加速度估计结果在滤波后产生近10mGal的影响;在数据采样间隔为1s时,1周的周跳对相位差分法的加速度估计结果产生数千mGal的误差。研究结果能为航空重力测量中利用PPP高精度估计重力仪加速度提供一定的理论指导,尤其对难以建站的测区的重力测量具有重大意义。 相似文献
99.
Kai Xiao Fuping Sun Maihang He Lundong Zhang Xinhui Zhu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(5):1638-1655
The integer ambiguity resolution (AR) of carrier phase is significant for Global Navigation Satellite System (GNSS) precise positioning. However, in kinematic case, single-epoch AR methods based on alone GNSS are usually not reliable due to the instable pseudorange accuracy. Moreover, the computation of classical AR method Least Squares Ambiguity Decorrelation Adjustment (LAMBDA) is large. Thus, the inertial measurement unit (IMU) is introduced, a new inertial-aided AR method that directly rounds the float ambiguity of BeiDou triple-frequency combined observations, which is characterized by long wavelength, low carrier-phase noise and ionospheric delay, is proposed. The mathematical model of the new method is derived first. Then the impacts of the carrier-phase noise, ionospheric delay and inertial navigation system (INS) position error on the AR success ratio of combined observation are analyzed through probabilistic approach. Based on above investigation, the combinations (0, ?1, 1), (1, 4, ?5) and (4, ?2, ?3) are selected to resolve the original ambiguity. A vehicular integrated navigation test is performed to demonstrate the proposed method. The results show that the average AR success ratios of the three selected combinations, whose float ambiguity errors are 0.041, 0.146, 0.279 cycle respectively, are above 97.25% without regard to low-elevation C05. With respect to positioning accuracy based on our AR method when compared with IE software, the east, north, up error RMS of position are 0.042, 0.024, 0.069 m, respectively. In terms of the AR recover after the BeiDou signals outage, as long as 62 s BeiDou signal complete outage, all the ambiguities of all satellites could be re-fixed immediately. Besides, during the 90 s signals partial outage, the AR is not influenced by the position error, since the float ambiguity errors are all below half-cycle. The research of this contribution demonstrates the effectiveness of the proposed new method, which indicates it is applicable to kinematic positioning, even in BDS degraded and denied environments. 相似文献
100.