共查询到20条相似文献，搜索用时 281 毫秒
1.
Nowadays, GPS receivers are very reliable because of their good accuracy and precision; however, uncertainty is also inherent in geospatial data. Quality of GPS measurements can be influenced by atmospheric disturbances, multipathing, synchronization of clocks, satellite geometry, geographical features of the observed region, low broadcasting coverage, inadequate transmitting formats, or human or instrumental unknown errors. Assuming that the scenario and technical conditions that can influence the quality of GPS measurements are optimal, that functional and stochastic models that process the signals to a geodetic measurement are correct, and that all the GPS observables are taken in the same conditions, it is still possible to estimate the positional errors as the difference between the real coordinates and those measured by the GPS. In this paper, three spatial linear mixed models, one for each axis, are used for modelling real-time kinematic GPS accuracy and precision, of a multiple-reference-station network in dual-frequency with carrier phase measurements. Along the paper, the proposed models provide an estimate of the “accuracy” in terms of bias defined as the difference between real coordinates and measured coordinates after being processed and “precision” through the standard errors of the estimated differences. This is done using ten different transmitting formats. Mapping and quantifying these differences can be interesting for users and GPS professionals. The performance of these models is illustrated by mapping positional error estimates within the whole region of Navarre, Spain. Sampled data have been taken in 54 out of the 211 geodetic vertex points of this region. Maps show interesting error patterns depending on transmitting formats, the different axes, and the geographical characteristics of the region. Higher differences are found in regions with bad broadcasting coverage, due to the presence of mountains and high degree of humidity. 相似文献
2.
顾及双差残差反演GPS信号方向的斜路径水汽含量 总被引：1，自引：1，他引：0
给出了顾及GPS双差残差反演斜路径水汽SWV的解算流程;然后详细给出了双差残差到非差残差的转化算法,并对算法进行了改进;最后利用并址的GPS和WVR实测数据对反演SWV算法进行了验证,结果证实改进的反演算法能以优于4 mm精度近实时估算SWV值,与目前国际研究精度在同一量级。 相似文献
3.
Xiaoliang Wang 《GPS Solutions》2011,15(2):121-128
An improved adaptive Kalman filter algorithm is presented to model error and process noise uncertainty. The adaptive algorithm
for model error is obtained by using an upper bound for the state prediction covariance matrix. The process noise is estimated
at each filter step by minimizing a criterion function, which was determined by measurement prediction. A recursive algorithm
is provided for solving the criterion function. The proposed adaptive filter algorithm was successfully implemented in GPS
relative navigation for spacecraft formation flying in high earth orbits with real orbit perturbations. Software simulation
results indicated that the proposed adaptive filter performed better in robustness and accuracy compared with previous adaptive
algorithms. 相似文献
4.
利用地面气象观测资料确定对流层加权平均温度 总被引：2，自引：0，他引：2
地基GPS气象学的核心思想是通过垂直方向上GPS信号的湿分量延时确定出可降水分 ,而这两个物理量之间的转换必须使用对流层加权平均温度。本文首先讨论了上述转换估计中加权平均温度的几种逼近方式及其容许误差 ,然后利用香港地区的地面和高空气象资料 ,采用逐步回归分析方法 ,建立了适合香港地区的对流层加权平均温度计算公式 ,通过数据分析表明 ,这个公式有效地消除了在香港地区使用Bevis经验公式引起的系统误差 ,较好地满足了地基GPS气象应用中实时性和高精度的要求。本研究也充分表明 ,在地基GPS气象研究中 ,应该利用本地区的气象资料来确定适合本地区的估计对流层加权平均温度的经验公式。 相似文献
5.
GPS信号相位延迟中包含很多大气信息,通过一定的方法可以从中获取有价值的大气参数。基于地基GPS相位延迟数据,提出了一种结合经验模式的一维变分同化获取大气折射率的方法。利用GPS相位延迟模拟数据进行同化试验,讨论了背景误差的设置对同化结果的影响,采用实测个例对该方法进行了验证。结果表明,该一维变分同化方法可行,并可获取高精度的0~60 km大气折射率。低层大气背景误差设置的准确程度会对整个高度范围内的同化效果产生影响。首次将同化获取的大气折射率应用于无线电波折射修正,取得了很好的修正效果,修正精度可达1 mm量级。 相似文献
6.
本文在现有单目视觉测量方法基础上,提出了一种相机真实俯仰角计算算法,结合图像快速相关匹配与定位算法,可完成桥梁挠度的快速精确测量。通过精度验证试验和挠度对比测试试验,得到了相应的结果,结果表明：①不考虑目标点真实俯仰角变化的测量方法在距离视场中心较远的位置测量结果中误差较大;②单目视觉方法测量结果与角钢作竖直向下的刚体位移保持一致;③单目视觉方法与GPS测量的挠度曲线变化趋势和测量数值基本一致。试验验证了本文方法的可行性及准确性,可为今后基于数字图像相关方法的土木工程变形测量技术研究提供参考。 相似文献
7.
Yanming Feng 《GPS Solutions》2001,5(2):1-11
Single-epoch point positioning with the global positioning system (GPS) is as accurate in low orbit as it is on the ground:
typically a three-dimensional rms accuracy of 20 to 30 m as the selective availability turns to zero. This is achieved at
any observation epoch without orbit dynamic information. With sophisticated models and filtering techniques onboard the spacecraft,
the orbit accuracy of a Low Earth Orbiter (LEO) can be improved to a few meters using the civilian broadcast GPS signals.
To achieve this accuracy autonomously in real time, an efficient onboard computing processor is required to carry out the
sophisticated orbit integration and filtering process.
In this paper, a new orbit integrator is presented that computes the nominal orbit states (the position and velocity) and
the state transition equations with numerical methods of integral equation, instead of differential equation usually used
for orbit computation. The algorithm is simple, and can be easily embedded in an onboard processor. The numerical results
demonstrate that the proposed method of the integral equation provides precise orbit predictions over several orbits. The
sequential filter based on the above integrator allows the use of simple orbit state equations to efficiently correct dynamical
model errors with precise GPS measurements or improve the orbits using GPS navigaion solutions from the 3D rms accuracy of
26 m to 3.7 m within a few hours of tracking. ? 2001 John Wiley & Sons, Inc. 相似文献
8.
GPS共视接收机短期观测资料处理算法研究 总被引：1，自引：0，他引：1
提出了一种新的基于总体最小二乘数据拟合的短期观测资料处理算法 ,同时考虑测量时刻和时差测量值的不确定性 ,可提高共视接收机输出的单站数据精度。超短基线单通道共视测量数据表明 ,使用新算法后 ,可以提高原始共视数据短期稳定度 相似文献
9.
10.
针对接收机的动态模型对GPS定位精度的影响,提出了一种基于多普勒频移观测的高动态GPS自适应滤波算法。该算法利用GPS伪距测量值以及利用信号载波的多普勒频移所获得的伪距率测量值,在GPS动态滤波中同时观测伪距和伪距率。借助于移动目标的运动矢量模型以及GPS定位误差模型建立了滤波方程。重点讨论了运用该模型进行Kalman滤波的实现过程。仿真实验表明,该模型与传统的方差自适应模型相比,位置精度提高了32%、速度精度提高了25%,应用本文算法能够提高定位精度和改善接收机的动态性能,拓宽高精度、高动态导航的应用范围。 相似文献
11.
实时获取智能移动终端的地理位置信息是增强现实（AR）实景智能导航系统实现的关键,为了提高智能终端GPS定位的精度,提出了一种基于卡尔曼滤波与改进的具有噪声的基于密度的聚类方法（DBSCAN）结合的GPS组合定位优化方法. 通过对GPS系统采集到的位置坐标数据进行卡尔曼滤波,去除较大的数据波动,控制定位误差范围,采用DBSCAN聚类算法进行分类去噪和二次聚类,对类中数据求得算术均值和类间数据总数进行加权求重心,确定位置坐标. 实验结果表明,提出的算法能有效提高GPS单点定位精度,减少定位误差,同时很好地满足了AR实景智能导航系统实时性和鲁棒性的要求. 相似文献
12.
手持GPS是一种依靠GPS卫星进行定位、导航、数据采集的测绘仪器,以其操作简单、便于携带,具有一定的测量精度,在油田的井位踏勘、道路巡检、井位导航、距离量算、概略坐标采集等勘探开发工作中,得到了十分广泛的应用。本文以数理统计学原理和测量误差理论为基础,对手持GPS实际采集的坐标数据进行了分析、处理、计算,求取了手持GPS接收机的定位精度和实际定位误差,为手持GPS的适用范围提供了参考。 相似文献
13.
David M. Gleason 《Journal of Geodesy》1996,70(5):263-275
A current pursuit of the geodetic community is the optimal integration of differential GPS (DGPS) and inertial navigation system (INS) data streams for precise and efficient position and gravity vector surveying. Therein a complete INS and multiple-antenna GPS receiver payload, mounted on a moving platform, is used in conjunction with a network of ground-fixed single antenna GPS receivers. This paper presents a complete, GPS-based, external updating measurement model for the applicable Kalman filter. The model utilizes four external observation types for every GPS satellite in-view: DGPS range differences, single phase differences, and single phase-rate differences; as well as the mobile, multipleantenna GPS receiver's measurement of theerrors in the INS's estimate of the phase difference between any two vehicle-borne GPS antennae. Although not widely conveyed in the geodetic world, the inertial navigation community has long known that traditional Kalman filter covariance propagation recurrences are inherently unstable when such highly accurate external updates are repeatedly applied (every 1 second) over long time durations. A hybrid square root covariance/U — D covariance factorization approach is a numerically stable alternative and is reviewed herein. The hybrid makeup of the algorithm is necessitated by the correlated nature of the fourth type of GPS external measurement listed above (each vehicle-borne GPS antenna formstwo baselines). Such measurement correlations require a functional transformation of the overall external updating model to permit the multiple updates (simultaneously available at each updating epoch) to be sequentially (and efficiently) processed. An appropriate transformation is given. Stable covariance propagation relationships are presented and the transformed Kalman gain is also furnished and its use in the determination of the externally updated error states is discussed. Specific DGPS/INS instabilities produced by the traditional recurrences are displayed. The stable alternative method requires about 25% more CPU time than the traditional Kalman recurrences. With the ever-increasing computational speeds of microprocessors, this added CPU time is of no real concern. 相似文献
14.
Precision real-time navigation of LEO satellites using global positioning system measurements 总被引：4，自引：3，他引：1
Continued advancements in remote sensing technology along with a trend towards highly autonomous spacecraft provide a strong
motivation for accurate real-time navigation of satellites in low Earth orbit (LEO). Global Navigation Satellite System (GNSS)
sensors nowadays enable a continuous tracking and provide low-noise radiometric measurements onboard a user spacecraft. Following
the deactivation of Selective Availability a representative real-time positioning accuracy of 10 m is presently achieved by
spaceborne global positioning system (GPS) receivers on LEO satellites. This accuracy can notably be improved by use of dynamic
orbit determination techniques. Besides a filtering of measurement noise and other short-term errors, these techniques enable
the processing of ambiguous measurements such as carrier phase or code-carrier combinations. In this paper a reference algorithm
for real-time onboard orbit determination is described and tested with GPS measurements from various ongoing space missions
covering an altitude range of 400–800 km. A trade-off between modeling effort and achievable accuracy is performed, which
takes into account the limitations of available onboard processors and the restricted upload capabilities. Furthermore, the
benefits of different measurements types and the available real-time ephemeris products are assessed. Using GPS broadcast
ephemerides a real-time position accuracy of about 0.5 m (3D rms) is feasible with dual-frequency carrier phase measurements.
Slightly inferior results (0.6–1 m) are achieved with single-frequency code-carrier combinations or dual-frequency code. For
further performance improvements the use of more accurate real-time GPS ephemeris products is mandatory. By way of example,
it is shown that the TDRSS Augmentation Service for Satellites (TASS) offers the potential for 0.1–0.2 m real-time navigation
accuracies onboard LEO satellites. 相似文献
15.
Xiuxiao Yuan Jianhong Fu Hongxing Sun Charles Toth 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(6):541-550
In traditional GPS-supported aerotriangulation, differential GPS (DGPS) positioning technology is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs). However, the establishment of GPS reference stations for DGPS positioning is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photography.Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actual aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a scale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail.The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However, if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each strip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales. 相似文献
16.
17.
针对城市环境中GPS动态定位系统的特点,提出了一种基于粒子滤波的GPS动态定位算法。与传统卡尔曼滤波算法相比,该算法利用观测伪距误差分布建立重要的密度函数,能够处理噪声符合非高斯分布的情况,且无需对观测方程线性化,提高了GPS动态定位的精度。通过实际算例分析,验证了该算法的有效性。 相似文献
18.
Precise estimation of residual tropospheric delays using a regional GPS network for real-time kinematic applications 总被引：7，自引：0，他引：7
A new method called Trop_NetAdjust is described to predict in real time the residual tropospheric delays on the GPS carrier
phase observables using the redundant measurements from a network of GPS reference stations. This method can not only enhance
the effectiveness and reliability of real-time kinematic users within the network, but also provide a valid approach to tropospheric
parameter variation forecasting. Trop_NetAdjust is theoretically based upon LS prediction criteria and enables the prediction
of residual tropospheric delays remaining after a standard model has been applied to the raw GPS measurements. Two cases are
analyzed, namely a first case when the delay is required for an existing satellite at a new point within the network and a
second case when the delay is required for a new satellite. Field tests were conducted using data collected in a network of
11 reference stations covering a 400×600 km region in southern Norway. The results were analyzed in the measurement domain
(ionospheric-free double-difference residuals) and showed improvements of 20 to 65% RMS errors using Trop_NetAdjust. The estimates
of the Trop_NetAdjust prediction accuracy were also obtained using the covariance analysis method. The agreement was consistently
better than 30% when compared with data from a real network.
Received: 28 February 2000 / Accepted: 9 January 2001 相似文献
19.
High-rate precise point positioning (PPP) to measure seismic wave motions: an experimental comparison of GPS PPP with inertial measurement units 总被引：2，自引：1，他引：1
Peiliang Xu Chuang Shi Rongxin Fang Jingnan Liu Xiaoji Niu Quan Zhang Takashi Yanagidani 《Journal of Geodesy》2013,87(4):361-372
High-rate GPS has been widely used to construct displacement waveforms and to invert for source parameters of earthquakes. Almost all works on internal and external evaluation of high-rate GPS accuracy are based on GPS relative positioning. We build an experimental platform to externally evaluate the accuracy of 50-Hz PPP displacement waveforms. Since the shake table allows motion in any of six degrees of freedom, we install an inertial measurement unit (IMU) to measure the attitude of the platform and transform the IMU displacements into the GPS coordinate system. The experimental results have shown that high-rate PPP can produce absolute horizontal displacement waveforms at the accuracy of 2–4 mm and absolute vertical displacement waveforms at the sub-centimeter level of accuracy within a short period of time. The significance of the experiments indicates that high-rate PPP is capable of detecting absolute seismic displacement waveforms at the same high accuracy as GPS relative positioning techniques, but requires no fixed datum station. We have also found a small scaling error of IMU and a small time offset of misalignment between high-rate PPP and IMU displacement waveforms by comparing the amplitudes of and cross-correlating both the displacement waveforms. 相似文献
20.
针对我国地区观测数据的实验定位结果精度问题,该文提出BDS/GPS非差误差改正数的实时动态定位方法,研究了BDS/GPS单参考站非差实时动态定位算法模型,流动站使用非差误差改正数,不需要进行双差观测值的组合。参考站将非差误差改正数传递给流动站,对流动站的观测值进行误差改正,可以直接固定流动站的模糊度。实验表明:在我国南方地区BDS精度要优于GPS,而在北方地区,BDS/GPS定位精度和GPS定位精度明显优于BDS。并且与单系统相比,组合系统的可视卫星数明显增加,改善了卫星空间几何分布结构,从而提高了导航定位的可用性和精度。 相似文献