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1.
Software-based global positioning system (GPS) receivers perform all the baseband signal processing and the high level functions on a general purpose processor. The heavy computational loads of the signal correlation in baseband processing make it difficult for software receivers to operate in real time. In order to improve the real-time performance, an enhanced bit-wise parallel algorithm has been developed in this study. The enhanced algorithm has been implemented and tested in a 12 channels real-time GPS software receiver. The system consists of a radio frequency front end, a data acquisition board and software that runs on a laptop with a Pentium-M 1.5 GHz processor running the Window® XP operating system. The data acquisition board packs the 2-bit intermediate frequency samples with a 2-bit in/8-bit out shift register and transfers the packed samples to laptop through a USB port. The software running on the laptop performs all the baseband and navigation processing in real time. The test results show that the enhanced algorithm significantly improves the real-time performance of the software receiver by reducing the computational operations for signal correlation by 50% compared with the existing bit-wise parallel algorithm. Furthermore, the enhanced algorithm also reduces the amount of required memory for storing data for signal correlation. 相似文献
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Architectures of Software GPS Receivers 总被引：6，自引：0，他引：6
There are various applications in which a Global Positioning System (GPS) sensor only down-converts and digitizes the received
GPS signal and sends the digitized data to a processor, where the processor software performs all the correlation, search/track
operations, navigation solution, and so on. Among the applications are military and commercial ones (e. g., GPS(Communication
handheld sets, people tracking systems).
A major problem with the Software GPS Receiver is the large computing resources required for correlation or acquisition of
the GPS signal. In this article, several possible approaches for reducing computing resources will be introduced and analyzed.
It will be shown that the performance of the GPS software design strongly depends on the features of the computer hardware.
Implementations will be described on the TMS320C6201 processor and the Pentium II.
Experimental results will be demonstrated by processing of real GPS signals. A complete 16-channel GPS receiver was implemented
on the single TMS320C6201 processor in real-time mode and on the Pentium II processor with a duty cycle of about 50%. ? 2000
John Wiley & Sons, Inc. 相似文献
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长周期精密测距码（P码）的直接捕获技术对提高导航接收机的性能十分关键,为了设计出高动态、低信噪比环境下的P码快速直接捕获接收机,采用部分匹配滤波器组实现伪码时域并行搜索,结合小点数的快速傅里叶变换（FFT）,将匹配滤波器输出的部分相关值进行功率谱分析,完成多普勒频率偏移的并行搜索。硬件实现时结合FPGA的特殊结构,提高资源利用率,同时采用并行流水机制处理ADC的采样信号,对于每一个采样点,均可以在下一个采样点到达之前完成该点的码相位和频率的二维搜索。对比国内外P码接收机的研究成果,算法在捕获时间上有很大改进。在信号功率为-165 dBW,伪码相位±1 s的时间不确定度,以及多普勒频率偏移±16 kHz的条件下,捕获时间小于10 s,完全适用于高动态环境下的P码快速直接捕获。 相似文献
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基于GPGPU的并行影像匹配算法 总被引：7，自引：1，他引：6
提出一种基于GPGPU的CUDA架构快速影像匹配并行算法,它能够在SIMT模式下完成高性能并行计算。并行算法根据GPU的并行结构和硬件特点,采用执行配置技术、高速存储技术和全局存储技术三种加速技术,优化数据存储结构,提高数据访问效率。实验结果表明,并行算法充分利用GPU的并行处理能力,在处理1280×1024分辨率的8位灰度图像时可达到最高多处理器warp占有率,速度是基于CPU实现的7倍。CUDA在高运算强度数据处理中呈现出的实时处理能力和计算能力,为进一步加速影像匹配性能和GPU通用计算提供了新的方法和思路。 相似文献
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描述了一种低成本的GPS/INS组合导航系统,经过理论推导得到了系统具体的实现方法,并通过市场上大量使用的低成本GPS模块和MEMS陀螺和加速度计实现了该系统。实际路测数据结果显示,该系统基本达到了理论预期。 相似文献
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提出了一种基于非线性盲辨识的自适应数字接收机技术。由于宽带雷电信号的时频特征未知或时变,在频域对宽带数字接收机输出信号中的谐波与互调分量进行识别和分选,并以其短时能量最小化作为其非线性行为模型参数的盲辨识准则,利用最速下降算法实现模型参数的自适应提取和更新,然后在线实时地对接收机输出信号进行非线性补偿。实验结果表明,该盲辨识数字接收技术可以将整机的无杂散失真动态范围（SFDR）提高近20dB,极有利于在强干扰存在时对微弱信号的接收与检测。 相似文献
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农村土地确权数据质量关系到后期维护管理与土地政策的实施及农民权益的保护,然而由于土地确权工作烦琐、经费支持不足、为降低成本而不按标准作业、影像资料分辨率低与现势性差等多方面原因,导致部分土地确权数据质量无法满足现行国家规范要求。本文分析了土地确权工作内容及图形与属性数据应该满足的条件和质量检查项目,基于ArcGIS平台及ArcEngine二次开发组件、空间图形关系判断算法、属性数据标准等研制了RLandRight农村土地确权检查软件,通过示范应用表明:可检查出图形与属性数据存在的问题,为数据修正提供依据;可保障土地确权数据质量,提高数据入库检查工作的效率。 相似文献
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随着计算机技术的发展，实时成像处理器技术的成熟，不但处理数据量越来越大，而且对成像质量要求也越来越高，实时成像处理中需要有自动聚焦算法。但是由于实时成像处理器的特殊结构和实时性要求，需要算法的计算量不能太大、不能太不确定。因此并不是所有的算法都适合用于实时处理。
主要介绍Map Drift算法的原理和实现步骤以及在实时成像处理器中的应用。文中对适合于实时成像处理器中应用的公式进行了推导，得到频域二次相位误差系数和相关峰位置的线性关系，并利用该关系在频域进行相位补偿，有效缩减迭代次数。利用一种插值来计算相关峰位置的方法，消除了离散化计算相关峰位置所带来的量化误差的影响，并在迭代过程中改进二次相位误差系数和相关峰位置关系的系数，对减少迭代次数，提高估计精度有一定帮助。最后给出仿真结果，验证算法的正确性。 相似文献
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J.-D. Bonjour 《The Photogrammetric Record》1990,13(75):389-405
Several generations of photogrammetric workstations have followed one another since the analytical plotter was developed at the beginning of the 1960s. The outcome of this evolution, resulting from important developments in mini- and microcomputers, is illustrated today by more and more powerful photogrammetric workstations based on distributed processing architecture. This paper introduces present day architectures, as well as hardware and software aspects of the various components of these systems including graphics workstation, real time processor, superimposition system, correlation system and special input/output devices. Finally, an attempt is made to outline the prospects for further evolution. 相似文献
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Currently, the GNSS computing modes are of two classes: network-based data processing and user receiver-based processing. A GNSS reference receiver station essentially contributes raw measurement data in either the RINEX file format or as real-time data streams in the RTCM format. Very little computation is carried out by the reference station. The existing network-based processing modes, regardless of whether they are executed in real-time or post-processed modes, are centralised or sequential. This paper describes a distributed GNSS computing framework that incorporates three GNSS modes: reference station-based, user receiver-based and network-based data processing. Raw data streams from each GNSS reference receiver station are processed in a distributed manner, i.e., either at the station itself or at a hosting data server/processor, to generate station-based solutions, or reference receiver-specific parameters. These may include precise receiver clock, zenith tropospheric delay, differential code biases, ambiguity parameters, ionospheric delays, as well as line-of-sight information such as azimuth and elevation angles. Covariance information for estimated parameters may also be optionally provided. In such a mode the nearby precise point positioning (PPP) or real-time kinematic (RTK) users can directly use the corrections from all or some of the stations for real-time precise positioning via a data server. At the user receiver, PPP and RTK techniques are unified under the same observation models, and the distinction is how the user receiver software deals with corrections from the reference station solutions and the ambiguity estimation in the observation equations. Numerical tests demonstrate good convergence behaviour for differential code bias and ambiguity estimates derived individually with single reference stations. With station-based solutions from three reference stations within distances of 22–103 km the user receiver positioning results, with various schemes, show an accuracy improvement of the proposed station-augmented PPP and ambiguity-fixed PPP solutions with respect to the standard float PPP solutions without station augmentation and ambiguity resolutions. Overall, the proposed reference station-based GNSS computing mode can support PPP and RTK positioning services as a simpler alternative to the existing network-based RTK or regionally augmented PPP systems. 相似文献
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Vinh T. Tran Nagaraj C. Shivaramaiah Thuan D. Nguyen Eamonn P. Glennon Andrew G. Dempster 《GPS Solutions》2018,22(1):24
The sampling frequency of a digitized intermediate frequency signal has a strong effect on the measurement accuracy of Global Navigation Satellite System (GNSS) receivers. The delay-locked loop tracking error is significant when the sampling frequency is an integer multiple of the code chipping rate, the so-called commensurate sampling frequency, and the number of distinct instantaneous residual code phases is low. This results in distortions of the correlation shape and discriminator functions that lead to a significant accuracy degradation. These effects are most pronounced when the sampling frequency is low. Notwithstanding, it is generally good for receivers to keep the sampling frequency to a minimum owing to the processing load and power consumption. It creates a challenge for existing GNSS signal processing techniques. Random, sine and sawtooth jitters have been found to mitigate these distortions considerably. A software algorithm and two hardware receiver implementations of these solutions are proposed. A register-based architecture can be directly applied to the conventional receiver architecture, while the increase in resource and power consumption is insignificant. A RAM-based design cannot only considerably minimize utilized resources but also slightly reduce the power consumption compared to the conventional architecture. 相似文献
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GPS interactive time series analysis software 总被引：4，自引：3，他引：1
Time series analysis is an important part of geodetic and geodynamic studies, especially when continuous GPS observations are used to explore areas with a low rate of deformation. In this domain, having precise and robust tools for processing and analyzing position time series is a prerequisite. To meet this requirement, a new software package called GPS Interactive Time Series Analysis was developed using the MATLAB language. Along with calculating basic statistics and quality parameters such as mean and variance, the software is capable of importing and visualizing different time series formats, determining and removing jumps and outliers, interpolating data, and producing numerical and publication quality graphical outputs. Furthermore, bivariate statistical analysis (such as correlation coefficients, curvilinear and nonlinear regression), residual analysis, and spectral analysis (such as auto-spectrum, Lomb–Scargle spectrum, evolutionary power spectrum, and wavelet power spectrum) form the main analysis features of the software. 相似文献
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地图制图软件中,图形编辑功能与其撤销/重做(Undo/Redo)是必不可少的。本文详细说明了基于Ora-cle数据库的地图制图软件中编辑模块的数据模型及其定义,提出了图形编辑的一般公式。并在此公式的基础上,提出了一种高效的Undo/Redo执行原理:在编辑过程中保存编辑类型和参数,在执行Undo/Redo时提取数据编辑类型和参数进行处理,并给出了具体的实现代码。 相似文献
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Geodetic VLBI correlation in software 总被引：1，自引：1，他引：0
Correlation algorithms for geodetic very long baseline interferometry (VLBI) can now be effectively implemented on parallel
computers of modest size. We have undertaken a detailed comparison of the output from a trusted geodetic correlator, one that
has supported global geodetic VLBI observations for many years, with the output of a software correlator implemented on a
small parallel computing cluster. We show that the correlator outputs agree closely, within expected error bounds, after accounting
for the differences in the adopted geometric delay models, and therefore that use of the software correlator is feasible for
geodetic VLBI processing, as a first step toward routine geodetic data processing. Recent developments in software correlation
for geodesy are discussed, including the possibility of real-time processing options. 相似文献