Showing papers on "Assisted GPS published in 2017"
01 Jan 2017
TL;DR: This research study explores the Global Positioning System (GPS), its history, and the process of discovery needed to create the most accurate GPS possible, as well as the contemporary applications of GPS technology.
Abstract: This research study explores the Global Positioning System (GPS), its history, and the process of discovery needed to create the most accurate GPS possible, as well as the contemporary applications of GPS technology. Starting with the first satellite in space, GPS has been a work in progress. Originally pursued by the military for improvements to military tactics, GPS has become integrated into the everyday lives of millions of people around the world. How GPS determines location is a dichotomy, with simplistic theory and complex application. Many factors go into GPS to provide a consistent, accurate location. The orbital planes the satellites are placed in provide 24/7 coverage globally, the L-band frequencies used were chosen specifically for the characteristics they possess, and the multiple atomic clocks installed on each satellite provide incredible accuracy down to the nanoseconds, which is quintessential in GPS accuracy. The applications in GPS are far reaching and more applications are continually being discovered. With as far as GPS technology has progressed, there are still several factors that degrade the signal and are a challenge to overcome. Many of these challenges can be corrected efficiently, however, others, such as scintillation and total electron content variability in the ionosphere, create major hurdles to overcome. Luckily, there are many programs that aid in the correction process of these hurdles. The History of GPS According to R. Saunders’ article A Short History of GPS Development, The Global Positioning System (GPS) has a long history of trial and error and refinement and improvement. It’s purpose has shifted from being a military strategic asset to commonplace among the general public with its use in traveling, farming, and even banking. The beginning of GPS, introduced with a simple idea, can be traced back to the Soviet Union in the late 1950’s. In 1957, the Soviet Union made history with successfully launching the first satellite in space. To track the satellite Sputnik, Physicists and Scientists at John Hopkins University’s Applied Physics Laboratory listened to the beeps Sputnik’s signals produced. They noticed that the beeps had a Doppler Effect or Doppler Shift as the satellite passed by. Much like the sound a siren makes as a fire truck approaches, then as it passes, the sound of the siren seems different. The change in timing between the beeps let the scientist know Sputnik’s location. This led to the idea of reversing that process, to give a location on the Earth. Using radio frequencies to determine location in a two dimensional plane had been around since WWII, but using satellites would push this technology into the three dimensional realm. The United States Navy, Army, and Air Force all began developing their own GPS satellites in the 1960’s, but this was no small task. In the early 1960’s, the Navy launched its first Transit Satellite. The failure of this satellite, however, was due to
248 citations
TL;DR: A novel hybrid fusion algorithm is proposed to provide a pseudo position information to assist the integrated navigation system during GPS outages and achieves better performance in the prediction of GPS position information than the normal artificial neural network (ANN) trained by Bayesian Regularization.
103 citations
29 Sep 2017
TL;DR: Chips Message Robust Authentication (Chimera) as mentioned in this paper employs the concept of time-binding, in which the spreading code is punctured by markers that are cryptographically generated using a key derived from the digitally signed navigation message.
Abstract: In this paper, Chips Message Robust Authentication, or Chimera, is proposed to jointly authenticate both the navigation data and the spreading code of a GPS civilian signal. Authentication schemes protect the user community, especially critical infrastructure users, against spoofing attacks by providing evidence that the received signal is from a reliable source. Chimera employs the concept of time-binding, in which the spreading code is punctured by markers that are cryptographically generated using a key derived from the digitally signed navigation message. The navigation message and the spreading code cannot be independently generated. Bit commitment ensures that a spoofer cannot generate the correct marker sequence until after it has been broadcast. Two variations are discussed: a “slow” channel for standalone users and a “fast” channel for more rapid authentication when out-of-band information is available. Appropriate performance metrics and architectures for Chimera are proposed, and the choice of specific parameters is explained in the context of expected performance. These design principles are illustrated with a specific implementation of Chimera for the GPS L1C signal.
60 citations
TL;DR: It is found that ANN-based real-time mode identification, enhanced by mode availability GIS layers, significantly outperforms the existing methods.
Abstract: Traditionally, departments of transportation (DOTs) have dispatched probe vehicles with dedicated vehicles and drivers for monitoring traffic conditions. Emerging assisted GPS (AGPS) and accelerometer-equipped smartphones offer new sources of raw data that arise from voluntarily-traveling smartphone users provided that their modes of transportation can correctly be identified. By introducing additional raster map layers that indicate the availability of each mode, it is possible to enhance the accuracy of mode detection results. Even in its simplest form, an artificial neural network (ANN) excels at pattern recognition with a relatively short processing timeframe once it is properly trained, which is suitable for real-time mode identification purposes. Dubai is one of the major cities in the Middle East and offers unique environments, such as a high density of extremely high-rise buildings that may introduce multi-path errors with GPS signals. This paper develops real-time mode identification ANNs enhanced with proposed mode availability geographic information system (GIS) layers, firstly for a universal mode detection and, secondly for an auto mode detection for the particular intelligent transportation system (ITS) application of traffic monitoring, and compares the results with existing approaches. It is found that ANN-based real-time mode identification, enhanced by mode availability GIS layers, significantly outperforms the existing methods.
59 citations
TL;DR: A series of experiments conducted for real environments using mass floating car data collected in Beijing and Shanghai shows that the ST-CRF method not only has better performance and robustness than other popular methods in low-frequency map matching but also solves the “label-bias” problem.
Abstract: Integrating raw Global Position System (GPS) trajectories with a road network is often referred to as a map-matching problem. However, low-frequency trajectories (e.g., one GPS point for every 1–2 min) have raised many challenges to existing map-matching methods. In this paper, we propose a novel and global spatial–temporal map-matching method called spatial and temporal conditional random field (ST-CRF), which is based on insights relating to: 1) the spatial positioning accuracy of GPS points with the topological information of the underlying road network; 2) the spatial–temporal accessibility of a floating car; 3) the spatial distribution of the middle point between two consecutive GPS points; and 4) the consistency of the driving direction of a GPS trajectory. We construct a conditional random field model and identify the best matching path sequence from all candidate points. A series of experiments conducted for real environments using mass floating car data collected in Beijing and Shanghai shows that the ST-CRF method not only has better performance and robustness than other popular methods (e.g., point-line, ST-matching, and interactive voting-based map-matching methods) in low-frequency map matching but also solves the “label-bias” problem, which has long existed in the map matching of classical hidden Markov-based methods.
59 citations
TL;DR: This work investigates whether the applicability of single-Frequency PPP can be extended by moving from using only GPS to using multiple Global Navigation Satellite Systems (GNSS), and shows that multi-GNSS SF-PPP indeed outperforms GPS-only SF- PPP in particular in case of reduced sky visibility.
Abstract: Precise Point Positioning (PPP) is a popular Global Positioning System (GPS) processing strategy, thanks to its high precision without requiring additional GPS infrastructure. Single-Frequency PPP (SF-PPP) takes this one step further by no longer relying on expensive dual-frequency GPS receivers, while maintaining a relatively high positioning accuracy. The use of GPS-only SF-PPP for lane identification and mapping on a motorway has previously been demonstrated successfully. However, the performance was shown to depend strongly on the number of available satellites, limiting the application of SF-PPP to relatively open areas. We investigate whether the applicability can be extended by moving from using only GPS to using multiple Global Navigation Satellite Systems (GNSS). Next to GPS, the Russian GLONASS system is at present the only fully functional GNSS and was selected for this reason. We introduce our approach to multi-GNSS SF-PPP and demonstrate its performance by means of several experiments. Results show that multi-GNSS SF-PPP indeed outperforms GPS-only SF-PPP in particular in case of reduced sky visibility.
57 citations
TL;DR: The proposed method can greatly improve the positioning accuracy, as compared with traditional pseudorange+Doppler GPS/IMU tightly coupled navigation systems.
Abstract: This paper presents how the time-differenced carrier phase (TDCP) can be implemented in nondifferential global positioning system/inertial measurement unit (GPS/IMU) tightly coupled navigation systems to improve positioning performance. The TDCP is expressed as a conventional TDCP, representing the carrier phase difference between two successive GPS epochs, and a modified TDCP, which is defined in this paper as the carrier phase difference between current and reference GPS epochs. Both of these two TDCP expressions are implemented in a GPS/IMU tightly coupled navigation Kalman filter as observations: The conventional TDCP with a more accurate approximation of the velocity integration is applied to estimate velocity, whereas the modified TDCP is used for position estimation. When initialized with a high-accuracy reference position, the proposed navigation strategy can achieve submeter positioning accuracy in the nondifferential mode without estimating ambiguities. Compared with the conventional TDCP-only method, the inherent position drift problem of the TDCP observations can also be avoided. The absolute positioning accuracy of the proposed conventional+modified TDCP measurement update method is determined by the reference position, since the TDCP, including conventional and modified TDCP, is a relative measurement. However, even when initialized with a low-accuracy reference position, the relative positioning accuracy (or precision) of the proposed method is still very high, and the reference positioning accuracy can be maintained, owing to the proposed method. The proposed method can greatly improve the positioning accuracy, as compared with traditional pseudorange+Doppler GPS/IMU tightly coupled navigation systems.
53 citations
TL;DR: The serious fluctuations of vehicle trajectories due to multipath reflectivity from high-rise buildings have been eliminated, thereby enabling the effective detection of real curved trajectories occurring at traffic intersections, and novel algorithms for automatically detecting road intersections and traffic rules are presented.
52 citations
TL;DR: The results indicate that successful instantaneous precise RTK positioning is feasible while using L1 GPS and E1 Galileo data, and that the SF 4-system model is competitive to DF GPS even when residual ionospheric delays are present.
Abstract: With the combination of the emerging GNSSs, single-frequency (SF) precise RTK positioning becomes possible. In this contribution we evaluate such low-cost ublox receiver and antenna performance when combining real data of four CDMA systems, namely L1 GPS, E1 Galileo, L1 QZSS, and B1 BDS. Comparisons are made to more expensive dual-frequency (DF) GPS receivers and antennas. The formal and empirical ambiguity success rates and positioning precisions will first be evaluated while making use of L1 + E1, so as to investigate whether instantaneous SF RTK is possible without the need of B1 BDS or L1 QZSS. This follows by an analysis of the SF 4-system model performance when the residual ionosphere can be ignored and modeled as a function of the baseline length, respectively. The analyses are conducted for a location in Dunedin, New Zealand, and compared to Perth, Australia with the better visibility of BDS and QZSS. The results indicate that successful instantaneous precise RTK positioning is feasible while using L1 GPS and E1 Galileo data, and that the SF 4-system model is competitive to DF GPS even when residual ionospheric delays are present. We finally demonstrate that when the impact from the ionosphere increases and more than one epoch is needed for successful ambiguity resolution, the SF 4-system model performance can still remain competitive to the DF GPS receivers. This is particularly true in Perth with more satellites and when higher than customary elevation cut-off angles need to be used to avoid low-elevation multipath.
51 citations
TL;DR: Criteria of distribution, auto- and cross-correlations, and spectral features of speed and acceleration are considered as possible features, and an approach to selecting the most significant, non-correlating features from among those is presented.
Abstract: For route planning and tracking, it is sometimes necessary to know if the user is walking or using some other mode of transport. In most cases, the GPS data can be acquired from the user device. It is possible to estimate user’s transportation mode based on a GPS trace at a sampling rate of once per minute. There has been little prior work on the selection of a set of features from a large number of proposed features, especially for sparse GPS data. This article considers characteristics of distribution, auto- and cross-correlations, and spectral features of speed and acceleration as possible features, and presents an approach to selecting the most significant, non-correlating features from among those. Both speed and acceleration are inferred from changes in location and time between data points. Using GPS traces of buses in the city of Tampere, and of walking, biking and driving from the OpenStreetMap and Microsoft GeoLife projects, spectral bins were found to be among the most significant non-correlating features for differentiating between walking, bicycle, bus and driving, and were used to train classifiers with a fair accuracy. Auto- and cross-correlations, kurtoses and skewnesses were found to be of no use in the classification task. Useful features were found to have a fairly large (>0.4) correlation with each other.
49 citations
TL;DR: A long-range and broadband aerial communication system using directional antennas (ACDA), which provides real-time communication capability for disasters where a fixed communication infrastructure does not exist, and proves the promising usage of directional antennas for long-distance Wi-Fi aerial communication.
Abstract: In this paper, we design and implement a long-range and broadband aerial communication system using directional antennas (ACDA). The system integrates Wi-Fi devices with aerial networks to quickly establish a Wi-Fi infrastructure in the air, which provides real-time communication capability for disasters where a fixed communication infrastructure does not exist. ACDA utilizes unmanned aerial vehicle (UAV)-carried directional antennas to extend communication range, increase throughput, and reduce interference. A GPS-based control algorithm is designed and implemented to automatically reject wind disturbance and align the directions of antennas in accordance with UAV movement. A received signal strength indicator-based decentralized initial scan algorithm is also designed and implemented to quickly establish initial connection between the UAVs. Simulation studies verify the effectiveness of the heading control and initial scan algorithm. Field tests are also conducted to evaluate the performance of overall system in terms of throughput and delay with respect to the increase of communication range. The ACDA prototype system achieves 48 Mb/s throughput at a distance of 300 m and 2 Mb/s at 5000 m, and proves the promising usage of directional antennas for long-distance Wi-Fi aerial communication. Practical use of this on-demand communication system to aid emergency response is also demonstrated through a case study in a real disaster drill.
TL;DR: In this article, the authors present a procedure to assess the performance of a timing system based on distributed GPS and one based on a mixture of GPS receivers and IEEE 1588 devices.
Abstract: Accurate timing is often required for the intelligent electronic devices (IEDs) used in transmission substations. A common method of achieving this is direct connection of a device to a local global positioning system (GPS) receiver and the use of its one-pulse-per-second synchronizing signal and the IRIG-B coded message. However, concerns about GPS reliability are encouraging the use of timing systems less dependent on the direct use of local GPS receivers. The IEEE 1588 protocol is a network-based time synchronization technique designed to coexist with IEC 61850 applications and deliver sub microsecond timing accuracy. Many utilities are now considering the adoption of IEEE 1588, but they need confidence in the reliability of this technology before it can be rolled out to real substations. Hence, comprehensive tests were undertaken on an IEEE 1588 timing system, to help gain insight into the limitations of the system. This paper presents a procedure to assess the performance of a timing system based on distributed GPS receivers and one based on a mixture of GPS receivers and IEEE 1588 devices. Test results indicate whichever system is selected, high quality devices and systems, with appropriate installation and engineering, are essential to satisfy the stringent $\pm 1\, \mu \text{s}$ accuracy requirements needed by critical IED applications.
23 Oct 2017
TL;DR: A signaling game framework in which the GPS receiver can strategically infer the true location when the attacker attempts to mislead it with a fraudulent and purposefully crafted signal to defend against the civil GPS signal spoofing for civilian UAVs is proposed.
Abstract: The Global Positioning System (GPS) is commonly used in civilian Unmanned Aerial Vehicles (UAVs) to provide geolocation and time information for navigation. However, GPS is vulnerable to many intentional threats such as the GPS signal spoofing, where an attacker can deceive a GPS receiver by broadcasting incorrect GPS signals. Defense against such attacks is critical to ensure the reliability and security of UAVs. In this work, we propose a signaling game framework in which the GPS receiver can strategically infer the true location when the attacker attempts to mislead it with a fraudulent and purposefully crafted signal. We characterize the necessary and sufficient conditions of perfect Bayesian equilibrium (PBE) of the game and observe that the equilibrium has a PLASH structure, i.e., pooling in low types and separating in high types. This structure enables the development of a game-theoretic security mechanism to defend against the civil GPS signal spoofing for civilian UAVs. Our results show that in the separating part of the PLASH PBE, the civilian UAV can infer its true position under the spoofing attack while in the pooling portion of the PLASH PBE, the corresponding equilibrium strategy allows the civilian UAV to rationally decide the position that minimizes the deviation from its true position. Numerical experiments are used to corroborate our results and observations.
TL;DR: In this article, a GPS/BDS/GLONASS combined real-time kinematic (RTK) positioning method for middle-long baseline is proposed, where a two-step AR strategy is adopted, where wide-lane and ionosphere-free observation model are used respectively.
Abstract: As China's BeiDou Navigation Satellite System (BDS) has become operational in the Asia-Pacific region, it is important to demonstrate the capabilities that a combination of GPS, BDS and GLONASS to high-precision positioning. Multi-constellation combination increases the available satellites and thus improves the positioning reliability. However at the same time, it will bring some challenges to the high-dimension ambiguity resolution (AR). In this contribution, a GPS/BDS/GLONASS combined real time kinematic (RTK) positioning method for middle-long baseline is proposed. In order to reduce the influence of troposphere and ionosphere delays on AR, a two-step AR strategy is adopted, where wide-lane and ionosphere-free observation model are used respectively. In the integer ambiguity search process, a partial ambiguity resolution (PAR) method is proposed to improve the AR performance. In the PAR method, satellite cutoff elevation, satellite number, AR success rate and ratio are used together to determine the a...
TL;DR: Two straightforward and easy to implement strategies will be described and analyzed, which improve the direct positioning accuracies for UAV-based mapping and surveying applications under challenging GPS measurement conditions.
Abstract: . For some years now, UAVs (unmanned aerial vehicles) are commonly used for different mobile mapping applications, such as in the fields of surveying, mining or archeology. To improve the efficiency of these applications an automation of the flight as well as the processing of the collected data is currently aimed at. One precondition for an automated mapping with UAVs is that the georeferencing is performed directly with cm-accuracies or better. Usually, a cm-accurate direct positioning of UAVs is based on an onboard multi-sensor system, which consists of an RTK-capable (real-time kinematic) GPS (global positioning system) receiver and additional sensors (e.g. inertial sensors). In this case, the absolute positioning accuracy essentially depends on the local GPS measurement conditions. Especially during mobile mapping applications in urban areas, these conditions can be very challenging, due to a satellite shadowing, non-line-of sight receptions, signal diffraction or multipath effects. In this paper, two straightforward and easy to implement strategies will be described and analyzed, which improve the direct positioning accuracies for UAV-based mapping and surveying applications under challenging GPS measurement conditions. Based on a 3D model of the surrounding buildings and vegetation in the area of interest, a GPS geometry map is determined, which can be integrated in the flight planning process, to avoid GPS challenging environments as far as possible. If these challenging environments cannot be avoided, the GPS positioning solution is improved by using obstruction adaptive elevation masks, to mitigate systematic GPS errors in the RTK-GPS positioning. Simulations and results of field tests demonstrate the profit of both strategies.
29 Sep 2017
TL;DR: In this paper, the authors investigate on precise positioning with a GPS and Galileo enabled chipset embedded in a smartphone and evaluate the benefit of tracking different GNSS constellations in terms of accuracy and convergence time.
Abstract: The main objective of this work is to investigate on precise positioning with a GPS and Galileo enabled chipset embedded in a smartphone. The analysis is carried out with code and carrier-based algorithms in different scenarios: simulated, stationary, pedestrian and vehicular. The areas investigated are precise positioning with single frequency, the benefits of multi-constellation GNSS and raw data quality provided by a smartphone. Currently the smartphones use only one frequency (L1): this is an important constraint in the design of the precise positioning algorithm mainly due to ionospheric effect. Hence, the work is based in two main algorithms: the first uses the carrier phase differential approach (Static or Kinematic) in conjunction of a reference GNSS networks; the second is based on the variometric approach using the VADASE algorithm, as the previous it uses the carrier phase but without external data. Modern GNSS chipsets are multi-constellations (GPS, GLONASS, Galileo, Beidou) and the increased number of satellites that can be tracked allows to increase the convergence time and to estimate the user's position very precisely. In the proposed work, at least the GPS+Galileo combination is considered. The purpose is to evaluate the benefit of tracking different GNSS constellations in terms of accuracy and convergence time. To develop software capable of this type of positioning, or perform these computations with existing software, pseudoranges and carrier-phase measurements are required. In principle, after the release of the N version of the Android operating system, the raw data are obtainable from a phone or tablet. However, from a technical point of view, the raw data, especially the carrier-phase, are not directly available in standard format and must be properly parsed.
The paper analyses the main errors sources’ of the GNSS chipset embedded in smartphone. The primary error source on smartphones lies not in the GNSS chipset, which actually offers great performance in terms of tracking availability and codebased accuracy, but in the antenna, whose chief failing is its poor multipath suppression. High accuracy positioning requires a stable antenna position for referring the position. However, moving smartphones are constantly changing attitude (which affects the antenna gain also), altitude (e.g. when the smartphone is kept in hand along the body or in front of the face for reading) and obstruction conditions. In order to quantify the impact of these scenarios, tests with internal and external antenna have been conducted.
TL;DR: An embedded system for monitoring the livestock grazing behavior is presented, based on an embedded circuit to process the sound produced by the animal in order to detect, classify and quantify events of ruminant feeding behavior.
TL;DR: This research presents a novel Cooperative Localization scheme that utilizes Round Trip Time (RTT) for inter-vehicle distance calculation, integrated with Reduced Inertial Sensor System (RISS) measurements to update the position of not only the vehicle to be localized, but its neighbors as well.
01 Jul 2017
TL;DR: This paper inspected individual energy consumption of the components in a GPS tracker and proposed a novel energy efficient, small wristband by integrating the latest LoRa communication and GPS duty cycling technologies, which is able to support up to 40 hours continuous GPS tracking with a frequent 60 seconds location update rate.
Abstract: Continuous GPS tracking devices always suffer short battery life when used by caregivers to reduce the risk of wandering to dangerous areas by dementia patients. Currently the best existing tracker for dementia patients on the market only supports less than 10 hours battery life with a gigantic battery. It not only requires daily battery charging from patients/caregivers, but also becomes a very restrictive device. In this paper we inspected individual energy consumption of the components in a GPS tracker and proposed a novel energy efficient, small wristband by integrating the latest LoRa communication and GPS duty cycling technologies. We verify our prototype's communication distance and energy efficiency through extensive experiments in the real world. Our model and data show the GPS wristband is able to support up to 40 hours continuous GPS tracking with a frequent 60 seconds location update rate. Its range also spans 3km, effectively monitoring patient locations.
TL;DR: A mobile application was developed that would enable users to create their own soils database consisting of GPS location and soil color data gathered using the application and a mobile sensor that produces multiple color results, including Munsell color notation.
01 Jan 2017
TL;DR: The results suggest that cruising in San Francisco, CA and Ann Arbor, Michigan is acute in some locations but overall experienced in less than 5–6% of vehicle trips, and that it accounts for less than 1%" of vehicle travel in these cities–considerably less than in previous estimates.
Abstract: This paper presents a method for determining parking search behavior using GPS traces. The research takes advantage of a GPS based household travel survey, an extensive dataset of GPS with video, and a commercially purchased set of trip segments. Strategies for data cleaning, matching traces to digitized networks, assessing the probability that a trace is of good quality, and strategies for determining whether or not a trip involves excess travel due to parking search are described. We define and operationalize two definitions of excess search – popularly known as cruising. Our results suggest that cruising in San Francisco, CA and Ann Arbor, Michigan is acute in some locations but overall experienced in less than 5–6% of vehicle trips, and that it accounts for less than 1% of vehicle travel in these cities–considerably less than in previous estimates.
07 Nov 2017
TL;DR: The goal of this dataset is to standardize and formalize the challenge of accurate vehicle self-localization and provide a benchmark to develop and evaluate algorithms.
Abstract: One of the biggest challenges in automated driving is the ability to determine the vehicleâĂZs location in realtime - a process known as self-localization or ego-localization. An automated driving system must be reliable under harsh conditions and environmental uncertainties (e.g. GPS denial or imprecision), sensor malfunction, road occlusions, poor lighting, and inclement weather. To cope with this myriad of potential problems, systems typically consist of a GPS receiver, in-vehicle sensors (e.g. cameras and LiDAR devices), and 3D High-Definition (3D HD) Maps. In this paper, we review state-of-the-art self-localization techniques, and present a benchmark for the task of image-based vehicle self-localization. Our dataset was collected on 10km of the Warren Freeway in the San Francisco Area under reasonable traffic and weather conditions. As input to the localization process, we provide timestamp-synchronized, consumer-grade monocular video frames (with camera intrinsic parameters), consumer-grade GPS trajectory, and production-grade 3D HD Maps. For evaluation, we provide survey-grade GPS trajectory. The goal of this dataset is to standardize and formalize the challenge of accurate vehicle self-localization and provide a benchmark to develop and evaluate algorithms.
TL;DR: A new enhanced tightly–coupled Cooperative Positioning (CP) technique is presented by adding the measurements from low-cost inertial sensors and the Doppler shift of the carrier of Dedicated Short-Range Communications (DSRC) signals.
Abstract: Relative position awareness is a vital premise for the implementation of emerging intelligent transportation systems. However, commercial Global Satellite Navigation Systems (GNSS) receivers do not satisfy the requirements of these applications. Fortunately, Cooperative Positioning (CP) systems, based on inter-vehicle communications, have improved performance of relative positioning in a Vehicular Ad Hoc Network (VANET). CP techniques rely primarily on measurements from the Global Positioning System (GPS) to deliver measurements or positions that describe the location of individual vehicles. In urban environments, the reduced quality or complete unavailability of GPS measurements challenges the effectiveness of any CP algorithm. In this paper, a new enhanced tightly–coupled CP technique is presented by adding the measurements from low-cost inertial sensors and the Doppler shift of the carrier of Dedicated Short-Range Communications (DSRC) signals. In the enhanced CP method proposed here, vehicles communicate their Inertial Measurement Unit (IMU) data and GPS measurements. Each vehicle fuses the GPS measurements and IMU data and the inter-node range-rates based on the Doppler shift of the carrier of DSRC signals. Based on analytical and experimental results, in a full GPS coverage environment, the new tight integration CP outperforms tight CP with Inertial Navigation System (INS), tight CP and differential GPS by at least by 6%, 15%, and 28%, respectively. In a GPS outage, the performance improvement can be up to 60%, 55%, and 66% respectively.
01 Apr 2017
TL;DR: A conceptual framework is proposed for determining the optimum GPS baseband receiver tracking channels in terms of power consumption and localization accuracy and multi-criteria analysis is a good strategy to visualize the trade-off between GPS design parameters, and to provide a dynamic power consumption planning.
Abstract: The Global Positioning System (GPS) passed a long way of development, starting from an advanced specialized tool, to a general purpose gadget used every day in our life. There are numerous presences of GPS in new technologies, applications and consumer products especially in Smartphone's and tablets. In GPS receiver design, power consumption and localization accuracy act as critical factors that affect the GPS receiver system outcome. Theoretically, increasing the Number of Required Tracking Channels (NRTC) in the GPS baseband receiver will increase the design complexity and size. Hence, the power consumption would significantly increase. Furthermore, to improve the location accuracy of a position, more satellites should be acquired and tracked by the receiver. This requires higher number of tracking channels in the receiver. Thus, optimizing the number of tracking channels to balance the conflict among performance parameters is a difficult and challenging task. The objective of this study is to highlight the need for an effective strategy to balance the tradeoff between conflicted GPS design parameters. A conceptual framework is proposed for determining the optimum GPS baseband receiver tracking channels in terms of power consumption and localization accuracy. Nine different operation modes of GPS receiver are evaluated by each design parameters, namely, power consumption, localization accuracy, and time with no position available for static and dynamic positioning. Multi-criteria analysis is a good strategy to visualize the trade-off between GPS design parameters, and to provide a dynamic power consumption planning.
TL;DR: A deeply coupled multireceiver vector tracking (MRVT) architecture that improves the reliability and robustness of GPS signal tracking and position estimation and is more robust to equipment malfunctions than the single GPS receiver is presented.
Abstract: Accurate, reliable, and robust global positioning system (GPS) localization is desirable for many navigation applications. Unfortunately, it is challenging for a single GPS receiver to always provide accurate positioning solutions. In urban environments, intermittent signal availability leads to degraded GPS signal tracking and position estimation of the single GPS receiver. In addition, equipment malfunction of the single GPS receiver results in inaccurate navigation solutions. This paper presents a deeply coupled multireceiver vector tracking (MRVT) architecture that improves the reliability and robustness of GPS signal tracking and position estimation. MRVT jointly tracks GPS signals received by multiple GPS receivers, mitigating GPS signal tracking disruptions, improving the reliability of GPS localization in periods of intermittent signal availability. In addition, the MRVT receiver is more robust to equipment malfunctions than the single GPS receiver. We implemented an MRVT receiver using commercial radio frequency front ends and our PyGNSS software. We experimentally validated the reliability of our MRVT receiver in periods of intermittent GPS availability experienced in downtown San Francisco. Our MRVT receiver exhibited consistent GPS signal tracking and position estimation as compared to vector tracking. In addition, we experimentally validated the robustness of our MRVT receiver to the failure of a single GPS receiver.
01 May 2017
TL;DR: The proposed method, called SatProbe, reverts to the GPS approach for its directness and robustness, but avoids its drawback by extracting only the number of visible satellites from the raw GPS data, instead of going through extensive computation to obtain a final position.
Abstract: Indoor-outdoor (IO) detection provides very useful hints for a mobile device to perform context-aware services. To that end, GPS presents a viable solution by relating a device's IO status with its positioning performance, which depends on the device's exposure to the open sky. This approach, however, is prohibitively expensive in terms of energy consumption and response time. Recent work has thus been focused on exploiting low-energy sensors such as light, cellular, and magnetic sensors to infer the IO status indirectly, at the cost of reduced adaptability or explicit user involvement. In this paper, we propose an improving solution to this problem. Our method, called SatProbe, reverts to the GPS approach for its directness and robustness, but avoids its drawback by extracting only the number of visible satellites from the raw GPS data, instead of going through extensive computation to obtain a final position. This metric provides a clear indicator of the IO status, yet can be obtained with great efficiency. Experiments on 79 raw GPS traces with 2595 detection points across a variety of environments show that SatProbe produces higher detection accuracy than previous solutions, with more than an order of magnitude reductions in energy consumption and detection time.
Patent•
30 Jun 2017
TL;DR: In this article, a real-time positioning method based on laser reflection strength was proposed, which can realize realtime accurate positioning in a complicated environment and can effectively improve driving safety of the unmanned aerial vehicle.
Abstract: The invention relates to an unmanned vehicle real-time positioning method based on laser reflection strength. The method comprises the following steps of S1, photographing two sides of a city road by an on-vehicle laser radar, obtaining a plurality of frames of point cloud data, extracting road edge points and converting the road edge points into a current vehicle coordinate system; S2, selecting the road edge points of which the z-axis coordinate value is in a preset range and obtaining coordinates of the road edge points in a GPS coordinate system, using the current GPS coordinate point of the unmanned vehicle as an original point, dividing a coordinate space for obtaining a grid map; S3, matching the gridded high-precision map with the grid map which is obtained in the step S2, thereby obtaining position of the unmanned vehicle on a high-precision map; and S4, predicating vehicle posture by means of a Kalman filter. Compared with prior art, the unmanned vehicle real-time positioning method can realize real-time accurate positioning in a complicated environment and can effectively improve driving safety of the unmanned aerial vehicle.
TL;DR: The results show that the combined GPS + GLONASS data produced almost the same level of accuracy with the GPS-only data if there is a sufficient number of GPS satellites with good geometry, and also reveal that a dm-level of accuracy can be achieved with the PPP technique in a dynamic environment.
10 May 2017
TL;DR: This work proposes a novel GPS spoofing detection scheme based on hardware oscillators that is cost-effective, secure, backward compatible with existing receivers, and does not require additional RF circuitry or network connection with other clocks for detecting attacks.
Abstract: The civilian Global Positioning System (GPS) is widely used for precise positioning, timekeeping, and synchronization in embedded systems As a result, emerging digital infrastructure such as the Internet of Things (IoT) are dependent on GPS to locate and synchronize \textit{Things} in the network From a security perspective, civilian GPS signals are vulnerable to malintent because they are not encrypted and can easily be spoofed Several countermeasures have been proposed to detect GPS spoofing attacks, but most of them require extensive signal processing capabilities and additional electronic components to capture and analyze RF signals These add-ons may not be available to IoT devices, and if present, they will affect the device\textquoteright s power budget significantly Therefore, new techniques for spoofing detection and survival are required before integrating GPS receivers with IoT devices and other critical infrastructures where energy and computation power are limited In this work, we propose a novel GPS spoofing detection scheme based on hardware oscillators Our design depends on measuring the frequency drift and offset of a free-running crystal oscillator with respect to the GPS signals In our secure GPS spoofing detector design the trust is intrinsic, \textit{ie}, the receiver only trusts the on-board free running local oscillator Intrinsic properties of these oscillators exhibit a strong correlation with the authentic GPS signals and any anomaly in this measurement will indicate potential attacks on the received GPS signals This proposed design is cost-effective, secure, backward compatible with existing receivers, and does not require additional RF circuitry or network connection with other clocks for detecting attacks
Patent•
13 Jun 2017
TL;DR: In this article, a GPS spatio-temporal data increment road network real-time updating and trace matching system is presented, which comprises a data acquisition module, GPS spatiotemporal data module, data pre-processing module, map trace matching module, a road network generating module, and an incremental road network updating module.
Abstract: The invention discloses a GPS (Global Position System) spatio-temporal data increment road network real-time updating and trace matching system, which comprises a data acquisition module, a GPS spatio-temporal data module, a data pre-processing module, a map trace matching module, a road network generating module and an increment road network updating module. According to the system, the acquired data recorded by a GPS positioner and provided with time and space attributes is pre-processed, a map is matched, a road is generated, a newly formed road section is compared with road network data recorded in a database, road network information is updated, and thus road network data is updated. According to the GPS spatio-temporal data increment road network real-time updating and trace matching system provided by the invention, the road network information is compared continuously with incremental data information, so that a real-time capability is realized, road position information is more accurate along with the increment of data, and roads which are not contained in the road network information are updated.