Application of Adaptive Kalman Filtering Algorithm in IMU/GPS Integrated Navigation System

The IMU(inertial measurement unit) error equations in the earth fixed coordinates are introduced firstly. A fading Kalman filtering is simply introduced and its shortcomings are analyzed, then an adaptive filtering is applied in IMU/GPS integrated navigation system, in which the adaptive factor is replaced by the fading factor. A practical example is given. The results prove that the adaptive filter combined with the fading factor is valid and reliable when applied in IMU/GPS integrated navigation system.     

An intelligent and autonomous MEMS IMU/GPS integration scheme for low cost land navigation applications

An intelligent scheme to integrate inertial navigation system/global positioning system (GPS) is proposed using a constructive neural network (CNN) to overcome the limitations of current schemes, namely Kalman filtering (KF). The proposed CNN technique does not require prior knowledge or empirical trials to implement the proposed architecture since it is able to construct its architecture “on the fly,” based on the complexity of the vehicle dynamic variations. The proposed scheme is implemented and tested using Micro-electro-mechanical systems inertial measurement unit data collected in a land-vehicle environment. The performance of the proposed scheme is then compared with the multi-layer feed-forward neural networks (MFNN) and KF- based schemes in terms of positioning accuracy during GPS signal outages. The results are then analyzed and discussed in terms of positioning accuracy and learning time. The preliminary results presented in this article indicate that the positioning accuracy were improved by more than 55% when the MFNN and CNN-based schemes were implemented. In addition, the proposed CNN was able to construct the topology by itself autonomously on the fly and achieve similar prediction performance with less hidden neurons compared to MFNN-based schemes.     

New method for single epoch, single frequency land vehicle attitude determination using low-end GPS receiver

Stand-alone, unaided, single frequency, single epoch attitude determination is the most challenging case of GNSS compass processing. For land vehicle applications, the baseline approximately lies in the plane of the local geodetic horizon. This provides an important constraint that can be exploited to directly aid the ambiguity resolution process. We fully integrate the constraint into the observation equations, which are transformed orthogonally. Our method can acquire the high-quality float solution by means of a heading search strategy. The fixed solution is obtained by weighted constrained integer least squares for each possible heading. The correct solution is identified by three consecutive steps: Kolmogorov?CSmirnov test, heading verification, and global minimizer of the fixed ambiguity objective function. The analysis focuses on single frequency, single epoch land vehicle attitude determination using low-end GPS receivers with very low precision of carrier phase and code measurements. The error analysis is given for choosing a proper baseline length in practical application. Experimental results demonstrate that this scheme can improve the ambiguity success rate for very short baseline.     

自适应卡尔曼滤波在GPS/DR组合导航中的应用

针对在观测条件较差的情况下卡尔曼滤波的鲁棒性较差,本文设计了一种自适应卡尔曼滤波模型。通过实际车载GPS/DR组合导航试验,结果表明该模型在观测质量较差的情况下能够抑制较大的偏差,相对于标准卡尔曼滤波模型,其平面定位精度提高了近一倍,达到2～3m。因此,在观测环境较差的情况下建议采用渐消自适应卡尔曼滤波模式进行组合导航。     

Design of an adaptive GPS vector tracking loop with the detection and isolation of contaminated channels

GPS Solutions - In vector tracking loop (VTL), the relativity among received signals is exploited to deeply integrate the entire information within signal processing channels. However, the tracking...     

An enhanced MEMS-INS/GNSS integrated system with fault detection and exclusion capability for land vehicle navigation in urban areas

We describe an enhanced quality control algorithm for the MEMS-INS/GNSS integrated navigation system. It aims to maintain the system’s reliability and availability during global navigation satellite system (GNSS) partial and complete data loss and disturbance, and hence to improve the system’s performance in urban environments with signal obstructions, tunnels, bridges, and signal reflections. To reduce the inertial navigation system (INS) error during GNSS outages, the stochastic model of the integration Kalman filter (KF) is informed by Allan variance analysis and the application of a non-holonomic constraint. A KF with a fault detection and exclusion capability is applied in the loosely and tightly coupled integration modes to reduce the adverse influence of abnormal GNSS data. In order to evaluate the performance of the proposed navigation system, road tests have been conducted in an urban area and the system’s reliability and integrity is discussed. The results demonstrate the effectiveness of different algorithms for reducing the growth of INS error.     

GPS positioning algorithm for a spinning vehicle with discontinuous signals received by a single-patch antenna

A GPS positioning algorithm is studied and applied to locate a spinning vehicle on which a single-patch antenna is mounted. Because the antenna is directional and the received signal is periodically discontinuous, the bits and frames cannot be synchronized to assemble the transmission time of the satellite signals. The characteristics of the signals received by a single-patch antenna are described. The means by which the tracking loop works with these discontinuous signals are analyzed and simulated. Aiming at spinning projectiles, the positioning algorithm forming differencing with respect to a reference satellite is applied to locate the spinning vehicle by using code phases obtained in the tracking of the discontinuous signals. Experiments were carried out, and the results showed that the positioning algorithm works properly on the spinning vehicle. The results revealed that the positioning error of the algorithm applied to a spinning vehicle is close to that of the conventional positioning method applied to a non-spinning vehicle.     

Generation of a consistent absolute phase-center correction model for GPS receiver and satellite antennas

The development and numerical values of the new absolute phase-center correction model for GPS receiver and satellite antennas, as adopted by the International GNSS (global navigation satellite systems) Service, are presented. Fixing absolute receiver antenna phase-center corrections to robot-based calibrations, the GeoForschungsZentrum Potsdam (GFZ) and the Technische Universität München reprocessed more than 10 years of GPS data in order to generate a consistent set of nadir-dependent phase-center variations (PCVs) and offsets in the z-direction pointing toward the Earth for all GPS satellites in orbit during that period. The agreement between the two solutions estimated by independent software packages is better than 1 mm for the PCVs and about 4 cm for the z-offsets. In addition, the long time-series facilitates the study of correlations of the satellite antenna corrections with several other parameters such as the global terrestrial scale or the orientation of the orbital planes with respect to the Sun. Finally, completely reprocessed GPS solutions using different phase-center correction models demonstrate the benefits from switching from relative to absolute antenna phase-center corrections. For example, tropospheric zenith delay biases between GPS and very long baseline interferometry (VLBI), as well as the drift of the terrestrial scale, are reduced and the GPS orbit consistency is improved.     

基于某卫星导航接收机的硬件抽象层SCA标准符合性测试设计

针对卫星导航信号波形在不同硬件平台上的可移植性问题,在系统中引入Mo-dem 硬件抽象层(MHAL)后,实现了不同计算单元上组件间管理的统一性和通信的标准化.为了便于测试MHAL的标准符合性[1],防止不同研制单位研制出互相不兼容的软件通信体系结构(SCA)通信设备,现以某卫星导航接收机为例说明具体硬件平台的MHAL测...     

Selection of LiDAR geometric features with adaptive neighborhood size for urban land cover classification

LiDAR has been an effective technology for acquiring urban land cover data in recent decades. Previous studies indicate that geometric features have a strong impact on land cover classification. Here, we analyzed an urban LiDAR dataset to explore the optimal feature subset from 25 geometric features incorporating 25 scales under 6 definitions for urban land cover classification. We performed a feature selection strategy to remove irrelevant or redundant features based on the correlation coefficient between features and classification accuracy of each features. The neighborhood scales were divided into small (0.5–1.5 m), medium (1.5–6 m) and large (>6 m) scale. Combining features with lower correlation coefficient and better classification performance would improve classification accuracy. The feature depicting homogeneity or heterogeneity of points would be calculated at a small scale, and the features to smooth points at a medium scale and the features of height different at large scale. As to the neighborhood definition, cuboid and cylinder were recommended. This study can guide the selection of optimal geometric features with adaptive neighborhood scale for urban land cover classification.     

Analysis of a variational Bayesian adaptive cubature Kalman filter tracking loop for high dynamic conditions

GPS Solutions - Under high dynamic conditions, a robust tracking loop is essential for accuracy positioning with the global position system. In previous studies, the extended Kalman filter...     

Influence of clock jump on the velocity and acceleration estimation with a single GPS receiver based on carrier-phase-derived Doppler

Since the Selective Availability was turned off, the velocity and acceleration can be determined accurately with a single GPS receiver using raw Doppler measurements. The carrier-phase-derived Doppler measurements are normally used to determine velocity and acceleration when there is no direct output of the raw Doppler observations in GPS receivers. Due to GPS receiver clock drifts, however, a GPS receiver clock jump occurs when the GPS receiver clock resets itself (typically with 1 ms increment/decrement) to synchronize with the GPS time. The clock jump affects the corresponding relationship between measurements and their time tags, which results in non-equidistant measurement sampling in time or incorrect time tags. This in turn affects velocity and acceleration determined for a GPS receiver by the conventional method which needs equidistant carrier phases to construct the derived Doppler measurements. To overcome this problem, an improved method that takes into account, GPS receiver clock jumps are devised to generate non-equidistant-derived Doppler observations based on non-equidistant carrier phases. Test results for static and kinematic receivers, which are obtained by using the conventional method without reconstructing the equidistant continuous carrier phases, show that receiver velocity and acceleration suffered significantly from clock jumps. An airborne kinematic experiment shows that the greatest impact on velocity and acceleration reaches up to 0.2 m/s, 0.1 m/s² for the horizontal component and 0.5 m/s, 0.25 m/s² for the vertical component. Therefore, it can be demonstrated that velocity and acceleration measurements by using a standalone GPS receiver can be immune to the influence of GPS receiver clock jumps with the proposed method.     

New Perspectives on the Use of GPS and GIS to Support a Highway Performance Study

In recent decades, rapid growth of travel volume has resulted in a significant increase in traffic congestion, accidents, environmental pollution and energy consumption. Accurate traffic data are drastically needed for effective evaluation of traffic systems in order to alleviate the impacts of increasing travel volume of the quality of life and economic development of urban areas. This article provides a discussion on a data acquisition methodology for highway traffic pattern recognition and congestion analysis by integrating data from the global positioning system (GPS) with a geographic information system (GIS). The GPS technology is a powerful tool in capturing continuous positioning and timing information, whereas the GIS is capable of storing, managing, manipulating, analyzing and displaying the acquired spatial information. Compared to previous studies, the effective integration of the two technologies allows for traffic analysis to be conducted at a finer resolution. The proposed method is illustrated with a case study on multiple major highway segments in Columbus, Ohio.     

Use of aerial photo-interpretation techniques for land evaluation of a part of Bolangir district,Orissa

The land evaluation has been of paramount importance for the planned development and resource utilization of an area, specially for locating better potential zones for increasing agricultural production. Large areas in the country are yet to be evaluated based on their productivity and potentiality. A case study was undertaken in a part of Bolangir district of Orissa, by using small scale aerial photographs.     

疫情背景下学生外出避险导航系统设计与实现

为了响应国家疫情常态化管理要求,弥补疫情背景下高校对于学生外出管理办法的缺陷。本文结合安卓（Android）开发、万维网（Web）开发、网络编程、派森（Python）爬虫技术设计并实现了一套疫情背景下学生外出避险导航系统。该系统能实时生成多尺度疫情风险地图,动态跟踪外出学生位置,自动划分疫情高风险区域并设置疫情围栏。系统主体部分为Android平台和Web平台,针对用户分别为学生和高校管理人员。Android平台负责获取学生出行数据,并包含出校扫码、轨迹记录、危险区域警告、避险导航、疫情风险地图等功能,Web平台负责接收管理学生数据,进行数据统计与分析。学生可以利用手机应用程序（APP）合理规划出行路线,在出现危险行为时发送提醒并根据危险级别向Web平台发送警告,提醒管理者采取措施。本系统在辅助学生安全外出的同时,也有效地帮助了高校对学生外出的管理工作。     

利用AUTOLISP编程进行房产图尺寸标注

房产测绘中,房产图尺寸标注是一项工作量很大的重复性工作。介绍了一个应用Autolisp语言开发的尺寸标注程序,提高了工作效率,而且能避免错误。     

Use of a Three-Domain Repesentation to Enhance GIS Support for Complex Spatiotemporal Queries

As the development of Geographic Information Systems (GIS) proceeds to advanced scientific and societal applications, there is an emerging need to enhance GIS support for complex spatiotemporal queries. Dynamic GIS representations (as opposed to static, map-based representations) that can integrate proper data elements in the production of geographic information are required. This paper demonstrates the use of a three-domain representation that facilitates compilation of higher-level information (such as frequency and rate) from preliminary data records (such as time and location) stored in a database. The three-domain representation is compared with snapshot, space-time composite, and spatiotemporal object models using a sample data set for forest transitions. While the three-domain representation is a normalization of these data models, it offers a conceptual alternative that enables GIS to represent spatiotemporal behaviors of geographic entities, in addition to entities as well as histories at locations as emphasized in most GIS data models. The comparison shows that the three-domain representation has combined the strengths of the space-time composite and spatiotemporal object models. Moreover, it enables aggregations of analytical use along with dynamic mappings between geographic concepts and locations, a distinct capability that takes GIS query processing beyond the level of information support offered by static map-based data models.     

The Use of Second-generation Wavelets to Combine a Gravimetric Quasigeoid Model with GPS-levelling Data

The merging of a gravimetric quasigeoid model with GPS-levelling data using second-generation wavelets is considered so as to provide better transformation of GPS ellipsoidal heights to normal heights. Since GPS-levelling data are irregular in the space domain and the classical wavelet transform relies on Fourier theory, which is unable to deal with irregular data sets without prior gridding, the classical wavelet transform is not directly applicable to this problem. Instead, second-generation wavelets and their associated lifting scheme, which do not require regularly spaced data, are used to combine gravimetric quasigeoid models and GPS-levelling data over Norway and Australia, and the results are cross-validated. Cross-validation means that GPS-levelling points not used in the merging are used to assess the results, where one point is omitted from the merging and used to test the merged surface, which is repeated for all points in the dataset. The wavelet-based results are also compared to those from least squares collocation (LSC) merging. This comparison shows that the second-generation wavelet method can be used instead of LSC with similar results, but the assumption of stationarity for LSC is not required in the wavelet method. Specifically, it is not necessary to (somewhat arbitrarily) remove trends from the data before applying the wavelet method, as is the case for LSC. It is also shown that the wavelet method is better at decreasing the maximum and minimum differences between the merged geoid and the cross-validating GPS-levelling data.