全球导航卫星系统的测高研究

以美国全球定位系统为代表的全球导航卫星系统具有广泛的应用领域，特点是能够在全球范围和近地空间，全天候地提供飞行器的位置、速度和时间信息。     

组合导航系统实验平台的设计与实现

随着科学技术的发展,人们对导航定位的要求越来越高,单一的导航方式已无法满足导航技术发展的需要,组合导航已成为导航技术发展的必然趋势.本文根据组合导航系统的概念,设计出一种通用的组合系统模型.该组合导航系统实验平台可以直接应用于目前的组合导航研究和实验,成为组合导航系统研究方面的有效工具,促进组合导航研究的发展.     

Tomographic determination of the spatial distribution of water vapor using GPS observations

With the advent of the GPS navigation system, a promising ground based technique has been introduced which makes it possible to estimate the amount of water vapor in the troposphere from operational GPS networks at relatively low additional costs. While the estimation of the integrated amount is currently well established, the determination of the spatial water vapor distribution and its temporal variation are still a major challenge. To account for the vertical resolution, several tomographic approaches were pursued. We developed the software package AWATOS (atmospheric water vapor tomography software) which is based on the assimilation of double differenced GPS observations. Applying a least-squares inversion, the inhomogeneous spatial distribution of water vapor is determined. An extensive investigation has been carried out in Switzerland. GPS measurements are performed by the dense permanent Swiss national GPS network AGNES of the Swiss Federal Office of Topography (swisstopo). A total of 40 equally distributed water vapor profiles have been estimated on an hourly basis. For the purpose of validation, 22 radiosonde profiles were used at the GPS and meteorological station Payerne. Furthermore, data of the numerical weather model aLMo (alpine model in Switzerland, MeteoSwiss) were compared with the tomographic results. An overall good agreement of the three methods with an rms of better than 1.6 g/m³ absolute humidity was achieved. The results show that AGNES can be used as a dedicated network for the purpose of GPS-tomography, using a horizontal resolution of approximately 50 km and height layers of 300–500 m thickness in the lower troposphere.     

Advanced architectures for real-time Delay-Doppler Map GNSS-reflectometers: The GPS reflectometer instrument for PAU (griPAU)

In recent years Global Navigation Satellite System’s signals Reflectometry (GNSS-R) has stood as a potential powerful remote sensing technique to derive scientifically relevant geophysical parameters such as ocean altimetry, sea state or soil moisture. This has brought out the need of designing and implementing appropriate receivers in order to track and process this kind of signals in real-time to avoid the storage of huge volumes of raw data. This paper presents the architecture and performance of the Global Positioning System (GPS) Reflectometer Instrument for PAU (griPAU), a real-time high resolution Delay-Doppler Map reflectometer, operating at the GPS L1 frequency with the C/A codes. The griPAU instrument computes 24 × 32 complex points DDMs with configurable resolution (Δf_Dmin = 20 Hz, Δτ_min = 0.05 chips) and selectable coherent (minimum = 1 ms, maximum = 100 ms for correlation loss Δρ < 90%) and incoherent integration times (minimum of one coherent integration period and maximum not limited but typically <1 s). A high sensitivity (DDM peak relative error = 0.9% and DDM volume relative error = 0.03% @ T_i = 1 s) and stability (Δρ/Δt = −1 s⁻¹) have been achieved by means of advanced digital design techniques.     

基于GPS的多基线姿态系统研究

在QUEST算法的基础上,提出了非单位向量前提下的四元数估计算法。该算法考虑了基线长度对精度的影响,将其应用于自制的GPS多基线姿态系统,计算载体的姿态角,验证系统及算法的精度。通过两次实验结果对比表明:该套GPS姿态系统具有较高的精度,非单位向量的四元数估计算法计算精度明显高于TRIAD算法。     

基于轨迹欺骗的无人机GPS/INS 复合导航系统干扰技术

在分析GPS欺骗干扰原理基础上,结合无人机(Unmanned aerial vehicle,UAV)GPS/INS复合导航系统的控制特点,设计了无人机导航系统中状态估计量的创新检测规则。采用直接轨迹欺骗与轨迹融合两种方法,实现了对无人机导航系统的侵入控制,达到了利用GPS欺骗干扰实现对无人机飞行轨迹进行控制的目的。通过理论推导和仿真分析给出了两种控制模式下归一化新息平方(Normalized innovation squared,NIS),指出当采用轨迹融合的控制方法时,不仅可实现无人机的轨迹欺骗,而且不易被检测,为GPS对抗提供了有效的干扰手段。     

提高GPS单频相位模糊度解算成功率的新方法

相位模糊度的成功解算是应用单频接收机进行高精度快速定位的关键。为了提高整周模糊度解算成功率,本文提出了一种新的算法,包括两项措施：(1)针对仅由几个历元组成的双差法方程系数阵存在着较严重病态性的结构特性,合理设计正则化矩阵,并在此基础上运用截断奇异值法求解模糊度实数解,使模糊度实数解更稳定和可靠,接近真实值;(2)在用最小二乘降相关平差(Least—squares ambiguity decorrrelation adiustment,LAMB—DA)方法进行模糊度搜索时,在Ratio检验的基础上,应用2个分析和比较的准则,对输出的多组候选整数模糊度向量进行分析和比较,甄别出正确的整数模糊度向量。算例表明,新方法不但缩短了模糊度解算所需要的观测时间,提高了模糊度实数解的可靠性和精度,而且显著地提高了整周模糊度解算的成功率。本文为单频接收机在高精度快速动态定位甚至实时定位等方面的广泛应用,提供了新的研究思路。     

GPS精密定向研究的实验

本文利用GPS三个天线的载波相位信息，先用三差法求出基线的初解，在此基础上再借助模糊度函数搜索初解，最后用双差法得到最终精确解，同时得出姿态角。文中主要结果是：基线相对定位精度达亚毫米级，定向精度在1米基线时为0.01度，基线越长，定向精度越高。     

基于模糊逻辑的GPS/DR组合导航系统地图匹配算法

利用地图匹配技术能够使用高精度的电子地图位置信息改善 GPS/ DR组合导航系统的定位精度。提出一种基于模糊数学方法和统计概率准则的地图匹配算法 ,在融合定位传感器数据和路段位置信息的基础上 ,通过模糊逻辑评判完成最佳匹配路段的挑选 ,并对匹配修正结果的可信度作出评价。仿真试验的结果证明该算法的有效性。     

GPS的发展及GPS／INS组合制导系统

主要论述全球定位系统 (GPS)的发展现状及前景规划 ;GPS和惯性 (INS)组合制导系统的发展以及新型固态惯性传感器的前景等