GPS Navigation Research Articles

Design and implementation of a model predictive observer for AHRS

A GPS-aided Inertial Navigation System (GAINS) is used to determine the orientation? position and velocity of ground and aerial vehicles. The data measured by Inertial Navigation System (INS) and GPS are commonly integrated through an Extended Kalman Filter (EKF). Since the EKF requires linearized models and complete knowledge of predefined stochastic noises? the estimation performance of this filter is attenuated by unmodeled nonlinearity and bias uncertainties of MEMS inertial sensors. The Attitude Heading Reference System (AHRS) is applied based on the quaternion and Euler angles methods. A moving horizon-based estimator such as Model Predictive Observer (MPO) enables us to approximate and estimate linear systems affected by unknown uncertainties. The main objective of this research is to present a new MPO method based on the duality principle between controller and observer of dynamic systems and its implementation in AHRS mode of a low-cost INS aided by a GPS. Asymptotic stability of the proposed MPO is proven by applying Lyapunov's direct method. The field test of a GAINS is performed by a ground vehicle to assess the long-time performance of the MPO method compared with the EKF. Both the EKF and MPO estimators are applied in AHRS mode of the MEMS GAINS for the purpose of real-time performance comparison. Furthermore? we use flight test data of the GAINS for evaluation of the estimation filters. The proposed MPO based on both the Euler angles and quaternion methods yields better estimation performances compared to the classic EKF.

Regional Multicriteria and Multimodal Route Planning System for Public Transportation: A Case Study

Nowadays, the use of computer-based route planners is popular among private and public transportation passengers. A large range of websites and GPS navigation devices provide such services for their users. Here, we present an algorithm used by a route planning system which operates on a complete public transport network of two regions from two countries, namely Hungary and Serbia. The algorithm can handle the pedestrian traffic between stops not too far from each other. It can take into account individual user preferences like walking distances and modes of transport. The graph representing the transport network was very large, but with the help of some speed-up techniques, we managed to create an effective search algorithm that is able to handle user requirements.

An Improved Ambiguity Resolution of Three Carriers in Precise Point Positioning

Precise point positioning (PPP) is of great importance in fields requiring coordinates with high accuracy, such as geophysics, meteorology, and geodesy. Compared with relative positioning restricted by the length of baseline, PPP using a single receiver is more flexible. Carrier phase observations with much higher precision than pseudorange measurements are used in the positioning process of PPP. However, accurate estimation of integer ambiguity associated with carrier phase observations is a prerequisite. Then the integrity of the phase observable can be completed as a range measurement with high precision. With triple-frequency signals of global navigation satellite system (GNSS) available, combinations of original observations with longer wavelengths and lower noises are preferable. In this paper, we propose an improved ambiguity resolution (AR) method based on the traditional bootstrapping method to make it suitable for PPP and increase the precision of AR and positioning. Virtual ambiguities of extra-wide-lane, wide-lane, and modified narrow-lane combinations are resolved first for their relatively better characteristics. Furthermore, extra pseudoranges are included to decrease the ionospheric delay which cannot be ignored as it is in relative positioning. Then, original ambiguities on the three frequencies can be recovered from the combined ambiguities using three linear equations which are independent to each other. Finally, the performance of the improved method is tested with real GPS navigation data on three frequencies which is provided by the international GNSS service. Compared with the traditional bootstrapping method, it shows that the ambiguity residuals of the improved method have decreased which indicates more accurate estimation. The precision of the positioning results has increased accordingly.

A South Pacific Cyclone-caused GPS Positioning Error and Its Impact on Remote Oceanic Island Communities

Satellite navigation gains importance in sustainable development of modern civilisation. With the increasing number of GNSS-based technology and socio-economic systems and services, satellite navigation has become an essential component of national infrastructure. This calls for novel requirements on GNSS positioning perfomance, and increasing need for resilient GNSS development. Here we examined the impact of rapidly developing tropical cyclone on GPS positioning performance degradation, and the resulting impact on oceanic non-navigation and navigation GPS applications. We presented the methodology for indirect simulation-based GPS positioning performance evaluation through utilisation of experimental GPS observations, GNSS Software- Defined Radio (SDR) receiver, and a statistical analysis and framework we developed in the R environment for scientific computing. We identified alteration of GPS positioning error components time series statistical properties, and discuss the potential impact on GPS-based services essential for remote oceanic island communities. Manuscript concludes with the summary of findings, proposal for recommendations on improved GNSS resilience, and an outline for future research.

Research and Simulation of GPS Navigation Signals

There are most important strategic significance in our country as well as the carrier rocket, ballistic missiles, the development of the manned space engineering that GPS signal simulation of satellite navigation system has. The structure and principle of GPS navigation and positioning signal were discussed in detail in this paper, with practicality as the starting point, the navigation message is transmitted by the use of pseudo random noise code phase-modulated signal, and the method of direct sequence spread spectrum modulation system is used to simulate the signal of GPS satellite orbit based on the MATLAB/Simulink platform. Then the simulation research and analysis of C/A code and P code in the frequency domain and time domain with it`s correlation is carried on, at the same time, the C/A code frequency domain is captured by using the fast Fourier transform method (FFT).finally the space transmission characteristics of GPS signal is simulated under Gaussian noise.it is show that the simulation result is close to the theoretical value, and the accuracy is better.

Modeling tropospheric wet delays with national GNSS reference network in China for BeiDou precise point positioning

During past decades, precise point positioning (PPP) has been proven to be a well-known positioning technique for centimeter or decimeter level accuracy. However, it needs long convergence time to get high-accuracy positioning, which limits the prospects of PPP, especially in real-time applications. It is expected that the PPP convergence time can be reduced by introducing high-quality external information, such as ionospheric or tropospheric corrections. In this study, several methods for tropospheric wet delays modeling over wide areas are investigated. A new, improved model is developed, applicable in real-time applications in China. Based on the GPT2w model, a modified parameter of zenith wet delay exponential decay wrt. height is introduced in the modeling of the real-time tropospheric delay. The accuracy of this tropospheric model and GPT2w model in different seasons is evaluated with cross-validation, the root mean square of the zenith troposphere delay (ZTD) is 1.2 and 3.6 cm on average, respectively. On the other hand, this new model proves to be better than the tropospheric modeling based on water-vapor scale height; it can accurately express tropospheric delays up to 10 km altitude, which potentially has benefits in many real-time applications. With the high-accuracy ZTD model, the augmented PPP convergence performance for BeiDou navigation satellite system (BDS) and GPS is evaluated. It shows that the contribution of the high-quality ZTD model on PPP convergence performance has relation with the constellation geometry. As BDS constellation geometry is poorer than GPS, the improvement for BDS PPP is more significant than that for GPS PPP. Compared with standard real-time PPP, the convergence time is reduced by 2–7 and 20–50% for the augmented BDS PPP, while GPS PPP only improves about 6 and 18% (on average), in horizontal and vertical directions, respectively. When GPS and BDS are combined, the geometry is greatly improved, which is good enough to get a reliable PPP solution, the augmentation PPP improves insignificantly comparing with standard PPP.

On-Board Video Recording Unravels Bird Behavior and Mortality Produced by High-Speed Trains

Large high-speed railway (HSR) networks are planned for the near future to accomplish increased transport demand with low energy consumption. However, high-speed trains produce unknown avian mortality due to birds using the railway and being unable to avoid approaching trains. Safety and logistic difficulties have precluded until now mortality estimation in railways through carcass removal, but information technologies can overcome such problems. We present the results obtained with an experimental on-board system to record bird-train collisions composed by a frontal recording camera, a GPS navigation system and a data storage unit. An observer standing in the cabin behind the driver controlled the system and filled out a form with data of collisions and bird observations in front of the train. Photographs of the train front taken before and after each journey were used to improve the record of killed birds. Trains running the 321.7 km line between Madrid and Albacete (Spain) at speeds up to 250-300 km/h were equipped with the system during 66 journeys along a year, totaling approximately 14,700 km of effective recording. The review of videos produced 1,090 bird observations, 29.4% of them corresponding to birds crossing the infrastructure under the catenary and thus facing collision risk. Recordings also showed that 37.7% bird crossings were of animals resting on some element of the infrastructure moments before the train arrival, and that the flight initiation distance of birds (mean ± SD) was between 60±33 m (passerines) and 136±49 m (raptors). Mortality in the railway was estimated to be 60.5 birds/km year on a line section with 53 runs per day and 26.1 birds/km year in a section with 25 runs per day. Our results are the first published estimation of bird mortality in a HSR and show the potential of information technologies to yield useful data for monitoring the impact of trains on birds via on-board recording systems. Moreover, recordings point to the use of the infrastructure by birds as a key issue leading to bird train-kill.

Refraction of Radio Waves on the Radio-Occultation Satellite-to-Satellite Paths as a Characteristic of the Atmospheric State

We present the results of analyzing the radio-wave refractive characteristics measured on the radio-occultation paths between the GPS navigation satellites and the FORMOSAT-3 research satellites in the central region of the European territory of Russia in 2007–2013. The diurnal, seasonal, and annual variations in the refraction angle at altitudes of 2 to 25 km are discussed. It is shown that the refraction angle can be used as an independent characteristic of the atmospheric state and its long-term variation trends. Diurnal and nocturnal variations in the refraction angle in the winter and summer seasons are analyzed. Trends in the atmospheric refraction variations over seven years are discussed.

Efficient Visibility Determination in Urban Scenes Considering Terrain Information

In this article, we introduce a novel occlusion culling method working on the server side to provide real-time navigation on web-based systems. Nowadays, virtual navigation in urban environments is a rising trend in several contexts such as tourism, GPS navigation systems, and video games. A city environment is usually associated with a complex data model that is better stored, maintained, and updated on a server system. Mobile devices are regular clients in these cases, demanding this information in a fast, reliable, and engaging way. Even though these gadgets have been increasing their capabilities in computation and visualization, the bottleneck is still the transmission of information over the network. The advantage of urban environments is that, from a user viewpoint, only a small portion of the scene is visible. This feature makes crucial the use of occlusion culling techniques working on the server side in order to transmit to the client side only the small set of visible elements compared to the whole scene. The input data are the city geometry from the 2D cadastral information system, the building textures, and DEM (Digital Elevation Model) files with the urban terrain features. In a first stage, the process creates a 2.5D urban model with all these data in preprocessing time. Then the client provides the user location point, and the server sends back the exact portion of visible city. This approach is implemented using polar diagrams for visibility determination and LOD (Level of Detail) techniques for further geometry reduction.

Grid-Based Method for GPS Route Analysis for Retrieval

Grids are commonly used as histograms to process spatial data in order to detect frequent patterns, predict destinations, or to infer popular places. However, they have not been previously used for GPS trajectory similarity searches or retrieval in general. Instead, slower and more complicated algorithms based on individual point-pair comparison have been used. We demonstrate how a grid representation can be used to compute four different route measures: novelty, noteworthiness, similarity, and inclusion. The measures may be used in several applications such as identifying taxi fraud, automatically updating GPS navigation software, optimizing traffic, and identifying commuting patterns. We compare our proposed route similarity measure, C-SIM, to eight popular alternatives including Edit Distance on Real sequence (EDR) and Frechet distance. The proposed measure is simple to implement and we give a fast, linear time algorithm for the task. It works well under noise, changes in sampling rate, and point shifting. We demonstrate that by using the grid, a route similarity ranking can be computed in real-time on the Mopsi2014 1 route dataset, which consists of over 6,000 routes. This ranking is an extension of the most similar route search and contains an ordered list of all similar routes from the database. The real-time search is due to indexing the cell database and comes at the cost of spending 80% more memory space for the index. The methods are implemented inside the Mopsi 2 route module.

A novel BeiDou weak signal acquisition scheme based on modified differential correlation

BeiDou signals are modulated with a secondary code of NH (Neumann–Hoffman) code to obtain a better positioning performance. The data bit rate increases to 1 kbps and bit transitions can occur in every 1 millisecond (ms) random sampling signal. As a result, the frequent bit transitions lead to an acquisition-sensitivity attenuation of classic integration algorithms. In order to improve acquisition sensitivity for BeiDou weak signals and resolve the problem that frequent bit transitions limit integration time, a novel BeiDou weak signal acquisition scheme based on modified differential correlation (M-DC) is proposed. First, conventional differential combination method is modified. The differential operation is moved from the post-correlator stage to the IF (intermediate frequency) samples to weaken the influence of data bit reversions. Second, an acquisition scheme implemented via fast Fourier transform is provided. Code phase and carrier frequency are estimated by one-dimensional search using fast Fourier transform. Third, power consumption and computation complexity of the proposed method are analyzed. Finally, Monte Carlo simulations and real data tests are conducted to analyze the performance of the proposed acquisition scheme. The results show that the proposed acquisition scheme can weaken the influence of data bit transitions to extend the integration time and enhance signal-to-noise ratio in weak signal environment. With the increase of accumulation time, the detection probability and acquisition sensitivity increase as well. The detection probability is 0.97 at CN0 (carrier-to-noise ratio) of 25 dB-Hz with an accumulation of 20 ms. This method is applicable to all kinds of BeiDou satellites and is also applicable to GPS, Galileo and other satellites navigation systems with or without secondary codes.

Ortho accuracy validation and analysis of GF-2 PAN imagery based on Beidou satellite navigation system and GPS

Ortho accuracy validation and analysis of GF-2 PAN imagery based on Beidou satellite navigation system and GPS

Marketing in the material construction of artifacts: A case study of a Portuguese navigation systems company

This article examines the social construction of technological innovations, focusing on how marketers of an information and communication technology (ICT) product interact with engineers in the creation of that product. The main purpose is to develop in empirical terms the concept of “material semiotics' rhetoric”. To this end it takes an in-depth look at a medium-sized Portuguese firm, in which we have over a period of five years observed how a GPS navigation device is generated and developed. We use the notions of “rhetoric” and “frames of reference” in adopting “material semiotics” as the theoretical background for observing the behaviors and interactions of the different actors involved in the construction of this technological artifact. The results show how the rhetorical framework shapes the technology, and also reveals the roles of different professionals when negotiating technical possibilities within the communicational strategies of a firm. The paper highlights the specific role of symbolic aspects in the material development of technology, stressing a relation between rhetoric and material semiotics.

Origin of the ahead of tsunami traveling ionospheric disturbances during Sumatra tsunami and offshore forecasting

AbstractThe presence of ionospheric disturbances associated with Sumatra 2004 tsunami that propagated ahead of tsunami itself has previously been identified. However, their origin remains unresolved till date. Focusing on their origin mechanism, we document these ionospheric disturbances referred as Ahead of tsunami Traveling Ionospheric Disturbances (ATIDs). Using total electron content (TEC) data from GPS Aided GEO Augmented Navigation GPS receivers located near the Indian east coast, we first confirm the ATIDs presence in TEC that appear ~90 min ahead of the arrival of tsunami at the Indian east coast. We propose here a simulation study based on tsunami‐atmospheric‐ionospheric coupling that considers tsunamigenic acoustic gravity waves (AGWs) to excite these disturbances. We explain the ATIDs generation based on the dissipation of transverse mode of the primary AGWs. The simulation corroborates the excitation of ATIDs with characteristics similar to the observations. Therefore, we offer an alternative theoretical tool to monitor the offshore ATIDs where observations are either rare or not available and could be potentially important for the tsunami early warning.

Providing a Resilient Timing and UTC Service Using eLoran in the United States

More and more systems are becoming solely dependent on GPS or other Global Navigation Satellite Systems (GNSS) for their precise position, timing, and frequency information. Along with this explosive growth comes an increasing awareness of GNSS vulnerabilities such as interference, jamming, and spoofing. eLoran is a high-power, low-frequency, ground-wave radio broadcast system, capable of providing 10-meter positioning accuracy, Stratum-1 frequency distribution, and UTC timing well within 1 μs across very large areas (1,000 mi). Application of differential corrections for timing further improves the accuracy to better than 100 ns. eLoran is a proven technology, well established for providing services very similar to those delivered by GNSS, with characteristics and failure modes that are complementary to GNSS. This paper discusses the general concept of eLoran timing and UTC distribution, and the current prototype service. It highlights plans for an initial four-station CONUS-wide timing service, which can be expanded to provide increased coverage and redundancy and deeper penetration into buildings. Additional stations enable positioning and navigation services. Copyright © 2017 Institute of Navigation

Salient features of the dayside low latitude ionospheric response to the main phase step-I of the 17 March 2015 geomagnetic storm

Based on TEC observations by India’s GPS Aided GEO Augmented Navigation (GAGAN) GPS network, we report the dayside low latitude ionospheric variations over the Indian region during the moderate main phase step-I of the 17 March 2015 geomagnetic storm. In addition, we assess the efficacy of GPS inferred TEC maps by International GNSS service (IGS) in capturing large scale diurnal features of equatorial ionization anomaly (EIA) over the Indian region during this period. Following the prompt penetration electric field (PPE) at ∼0605 UT, equatorial electrojet (EEJ) enhances by ∼55 nT over 75±3oE longitudes where main phase step-I is coincided with local noon. Initial moderate EIA gradually strengthens with the storm commencement. Although GAGAN TEC exhibits more intense EIA evolution compare to IGS TEC maps, latitudinal extent of EIA are comparable in both. The enhanced EEJ reverses by ∼0918 UT under the effect of overshielding electric field, the later is accompanied by northward turning of interplanetary magnetic field (IMF) Bz. The weakening of well evolved EIA reflects in IGS TEC maps after ∼45 min of the overshielding occurrence. In contrary, GAGAN TEC shows the corresponding feature after ∼0115h. Resurgence of EIA, following the PPE ∼1115 UT, shows up in GAGAN TEC but IGS TEC maps fails in capturing this feature. The observed low latitude TEC variations and EIA modulations are explained in terms of the varying storm time disturbance electric fields. The anomalies between the GAGAN TEC and IGS TEC maps are discussed in terms of the possible limitations of the IGS TEC maps in capturing storm time EIA variability over the Indian region.

A cooperative route choice approach via virtual vehicle in IoV

Popular navigation services are used by drivers both to plan out routes and to optimally navigate real time road congestion in internet of vehicles (IoV). However, the navigation system (such as GPS navigation system) and apps (such as Waze) may not be possible for each individual user to avoid traffic without creating congestion on the clearer roads, and it might even be that such a recommendation leads to longer aggregate routes. To solve this dispersion, in this paper, we first apply a concept of virtual vehicle in IoV, which is an image of driver and vehicle. Then, we study a setting of non-atomic routing in a network of m parallel links with symmetry of information. While a virtual vehicle knows the cost function associated with links, they are known to the individual virtual vehicles choosing the link. The virtual vehicles adapt the cooperation approach via strategic concession game, trying to minimize the individual and total travel time. How much benefit of travel time by the virtual vehicles cooperating when vehicles follow the cooperation decisions? We study the concession ratio: the ratio between the concession equilibrium obtained from an individual optimum and the social optimum. We find that cooperation approach can reduce the efficiency loss compared to the non-cooperative Nash equilibrium. In particular, in the case of two links with affine cost functions, the concession ratio is at most 3/2. For general non-decrease cost functions, the concession ratio is at most 2. For the strategic concession game, the concession ratio can approach to 1 which is a significant improvement over the unbounded price of anarchy.

Passive tracking of autonomous underwater vehicles (AUVs) using a low-cost acoustic data collection system

One challenge to harbor security is monitoring and tracking autonomous underwater vehicle (AUV) activity. A self-contained low-cost acoustic data collection system (acbox) has been developed and demonstrated for this purpose. The acbox consists of an 8-element configurable off-the-shelf hydrophone array, a data acquisition system, a GPS for timing and navigation, and a computer for data logging and processing. Noise data on the Bluefin SandShark and Bluefin 21-inch AUVs were collected using the configurable array in the Charles River and Massachusetts Bay. From this experiment, AUV noise characteristics were determined. The bearing to the AUV was estimated based on beamformed and frequency filtered data, and compared to logged AUV position. The bearing estimates based on propeller noise were consistent with the reported AUV position. These results for range estimation and filtering bearing were tested to provide improved vehicle localization. Performance in the presence of boat noise was also assessed. Moving forward, this work will be expanded to tracking AUVs from other AUVs for collision-avoidence and behavioral analysis for security monitoring applications. [Work supported by Battelle, DARPA, and Draper.]

A comparative analysis of the accuracy attainable for the local monitoring of Earth’s surface movements and deformation using the GPS and GLONASS navigation satellite systems

This paper is concerned with an experiment that was intended to compare the respective accuracies of local GNSS monitoring using observations by GPS and GLONASS satellites at different elevations above the horizon. We used data from continuous daily observation sessions in a local network during 3 months in the “static” mode. An analysis of parameters that characterize the accuracy and efficiency of displacement determinations showed that the combined GPS + GLONASS data processing has the highest accuracy at elevation angles greater than 15°. It is shown that the accuracy of GLONASS observations is not considerably worse than that of GPS. We note that the time-dependent variation of GLONASS observation is large.

An Analytical Model for BDS B1 Spreading Code Self-Interference Evaluation Considering NH Code Effects.

The short spreading code used by the BeiDou Navigation Satellite System (BDS) B1-I or GPS Coarse/Acquistiion (C/A) can cause aggregately undesirable cross-correlation between signals within each single constellation. This GPS-to-GPS or BDS-to-BDS correlation is referred to as self-interference. A GPS C/A code self-interference model is extended to propose a self-interference model for BDS B1, taking into account the unique feature of the B1-I signal transmitted by BDS medium Earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites—an extra Neumann-Hoffmann (NH) code. Currently there is no analytical model for BDS self-interference and a simple three parameter analytical model is proposed. The model is developed by calculating the spectral separation coefficient (SSC), converting SSC to equivalent white noise power level, and then using this to calculate effective carrier-to-noise density ratio. Cyclostationarity embedded in the signal offers the proposed model additional accuracy in predicting B1-I self-interference. Hardware simulator data are used to validate the model. Software simulator data are used to show the impact of self-interference on a typical BDS receiver including the finding that self-interference effect is most significant when the differential Doppler between desired and undesired signal is zero. Simulation results show the aggregate noise caused by just two undesirable spreading codes on a single desirable signal could lift the receiver noise floor by 3.83 dB under extreme C/N0 (carrier to noise density ratio) conditions (around 20 dB-Hz). This aggregate noise has the potential to increase code tracking standard deviation by 11.65 m under low C/N0 (15–19 dB-Hz) conditions and should therefore, be avoided for high-sensitivity applications. Although the findings refer to Beidou system, the principle weakness of the short codes illuminated here are valid for other satellite navigation systems.