面向CORS的精密定位服务中间件平台的设计

目前，卫星定位连续运行参考站网相关技术的应用与研究是测绘界研究的热点之一，国内外各类CORS正相继建立。本文针对CORS服务体系的数据共享和服务共享问题，从软件工程角度对CORS的数据采集、处理、计算、分发、服务等方面作了进一步梳理，建立了较完备的网络体系和软件体系模型，提供了一个较完备的面向CORS的中间件平台设计思路。本文的设计成果和实践，可有效地改善当前CORS领域软件开发现状中软件和研究成果保密、软件功能单一、无统一的开发标准和架构模型等问题，具有一定的实用价值。     

GNSS软件无线电接收机及典型案例

介绍了GNSS软件无线电接收机和它与传统接收机相比的优缺点，并引述了典型的GNSS软件接收机及其应用。     

Development and testing of a new ray-tracing approach to GNSS carrier-phase multipath modelling

Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8 cm for the Global Positioning System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation, but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite–reflector–antenna geometry and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method will have important practical applications for correcting for multipath in well-constrained environments (such as at base stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can be used to simulate realistic multipath errors for various performance analyses in high-precision positioning.     

10 Hz or 10 s?

Data sampling frequencies in many kinematic GNSS applications are often in the range of 2–10 Hz or even higher. In contrast, the sampling frequency of standard reference stations is usually not higher than 1 Hz, and many stations even deliver data at sampling intervals as large as 30 s. An easily implemented algorithm for data interpolation will be presented and it will be demonstrated that interpolation of pseudorange and carrier phase reference station data is possible at a high level of accuracy. This technique—which has not received proper attention so far—is helpful to reduce data storage capacity for postprocessing applications, but and can also be beneficial for real-time applications suffering from slow data links. Results of test trials indicate that a standard deviation better than 2 mm can be reached for interpolated carrier phases collected at reference sites sampling data with 5-s intervals in double difference mode. These interpolated double difference data obviously still follow a Gaussian distribution. A trend function for the expected standard deviation of interpolated double difference carrier phase measurements will be presented. From this function, a recommendation for an optimal sampling rate of reference station data can be derived which is close to 10 s.     

青藏高原大气可降水量单站观测对比分析

为了探讨青藏高原大气可降水量观测资料的可靠性,对2015年6-9月西藏申扎、改则和那曲3站地基GNSS遥感的大气可降水量、同址探空观测的大气可降水量、风云三号可见光红外扫描辐射计反演的晴空大气可降水量、MODIS大气可降水量和NCEP可降水量进行对比分析。结果表明:探空可降水量和地基GNSS可降水量的偏差较小,均低于2.5 mm。风云三号可降水量明显偏低,与其他观测结果的偏差超过6 mm。全自动探空可降水量离散程度较L波段探空大,均方根误差超过4 mm。      

GNSS形变监测时间序列的粗差数据处理方法

针对GNSS形变监测的传统粗差探测算法性能受限于数据长度的问题,提出基于小波分析的一阶导数粗差剔除法。首先使用新算法对原始信号进行粗差剔除,再利用广义延拓插值补充残缺点。实测算例结果表明,新算法执行时间是3倍中误差法（3σ法）的0.01倍,插值后与真实值偏离仅0.03 mm,远优于其他传统粗差探测手段。     

插补GNSS坐标时间序列的改进DINEOF算法

针对GNSS坐标时间序列插补中数据插值经验正交函数（data interpolating empirical orthogonal functions,DINEOF）算法受低相关度站点影响、连续长空缺插值效果欠佳的问题,提出相关数据插值经验正交函数（coefficient data interpolating empirical orthogonal functions,CDINEOF）算法。首先计算目标站点与其周围站点数据的相关度,然后筛选出相关度较高的数据构建观测矩阵,最后采用DINEOF算法对观测矩阵中的缺失数据进行插补。通过模拟数据和实测数据验证新方法的可行性,并与DINEOF算法和多项式插值法的结果进行对比分析。模拟数据实验结果表明,当观测数据存在连续长空缺时,CDINEOF算法的插值效果优于DINEOF算法和多项式插值法。实测数据实验结果表明,CDINEOF算法在保留方差最大化方面效果最好,与DINEOF算法和多项式插值法相比分别提升了11.8%和6.7%。     

2021年漾濞6.4级地震前地壳形变分析

利用2019-05-20~2021-05-20云南及周边54个GNSS基准站观测数据,基于最小二乘配置法求取云南地区速度场、应变场,并结合2021-05-21漾濞6.4级地震近场、远场区域的GNSS基线长度时间序列,分析地震前地壳形变特征。结果表明,震前云南西边界SSW方向运动增强,沿怒江断裂带呈发散性运动状态,震中附近的近场速度值变化不大,区域速度场异常变化不明显;震前研究区整体面膨胀率值下降至原来的0.37倍左右,同时最大剪应变率、主应变率也急剧下降,说明震前区域地壳应变积累明显减弱,而震中位于张、压交替的零值线上。GNSS基线长度时间序列结果显示,震前地震近场区域的GNSS基线异常变化不明显,而远场区域的GNSS基线出现偏离长期背景的趋势异常变化,基线KMIN-YNYM在趋势压缩背景下反向加速拉张,背离趋势运动8.4 mm,基线YNLP-KMIN在趋势压缩背景下加速压缩,背离趋势运动6.4 mm,基线YNLP-YNDZ在趋势变形较平稳的背景下加速压缩,背离趋势运动8.1 mm,基线YNSM-YNLP在趋势拉张背景下加速拉张,背离趋势运动7.8 mm,可判断震前区域应力平衡状态被打破,诱发了地震。     

顾及水汽衰减因子的中国区域大气可降水量模型的建立与分析

提出一种顾及水汽衰减因子的PWV估算模型,通过输入地面大气水汽压和水汽衰减因子获得PWV,并选取2018年中国地区85个探空测站和7个IGS测站1 a的观测数据用于验证新模型的精度。结果表明,在已知当日水汽衰减因子的情况下,模型估算的PWV精度约为2 mm;也可通过GPT2w格网内插得到任意位置的水汽衰减因子,其结果精度与传统的一次多项式模型相当,但新模型的作用范围更广、适用性更强。     

安卓智能手机GNSS数据筛选方案研究

通过设置两种不同的遮挡环境,对测地型接收机和智能手机静态采集的测量数据进行对比分析。结果表明,智能手机可接收部分非直射卫星信号,受多路径效应干扰明显。根据非直射卫星信号的数据特征设计智能手机原始GNSS数据筛选方案,静态定位实验结果表明,应用数据筛选方案能够显著提升智能手机在复杂环境下的定位精度。智能手机SPP定位算法和RTK定位算法平面方向的定位精度可提升20%~40%,高程方向的定位精度可提升30%~60%。