Kinematic Scenarios Research Articles

A reduced-condition-number algorithm for single-frequency precise point positioning based on regularized Kalman filter

Single-frequency receivers are low cost and portable, thus being widely applied in engineering; the extended Kalman filter (EKF) is commonly used to perform single-frequency precise point positioning (SF-PPP). However, the positioning performance of SF-PPP is seriously influenced by various errors. Due to the large process noise and initial variance of the estimated parameters, the weight matrix of state parameters will be ill-conditioned, and since the noise of the pseudo-range is much higher than that of the carrier phase, the weight matrix of observations presents as ill-conditioned. Additionally, the condition number of the normal matrix will jump on the conditions of cycle slip, new emerging satellites, and signal outages. To reduce the condition number of the normal matrix, the regularized Kalman filter (RKF) algorithm is proposed, with additional support for the maximum variance matrix and singular value decomposition, thereby improving the accuracy and stability of SF-PPP. Through static and dynamic experiments, it is found that the proposed method can reduce both the ill-conditioning of the weight matrices of the observations and the state parameters. The condition number of the normal matrix is <500 per epoch, and the convergence time is shortened by >40%. Compared with the SF-PPP using EKF, centimeter-level static positioning accuracies of 1.13, 0.73, and 2.92 cm and decimeter-level kinematic positioning accuracies of 12.5, 10.8, and 27.3 cm in the east, north, and vertical components, respectively, using RKF; this yielded 38.3, 29.8, and 45.2% and 39.6, 41.9, and 21.3% improvement in the static and kinematic scenarios, respectively.

Simulating tectonically controlled fractal landscape evolution in the Three Rivers Region (SE Tibetan Plateau margin)

The long-term development of fluvial landscapes is sensitive to tectonic movement. This is the case for the Three Rivers Region, located on the southeastern margin of the Tibetan Plateau, where it is critical for understanding the continuous collision and compression between the Indian and Eurasian plates. However, quantitative perspectives on this landscape evolution are lacking. Based on present global positioning system (GPS) data, a quantitative expression of two phases of regional deformation, a northeast-southwest shortening and dextral shear deformation, was proposed to represent the continuous Indian-Eurasian collision. By incorporating this tectonic pattern into a landscape evolution model and integrating the regional differential uplift, the numerical results quantitatively present a dynamic shaping of the Nu, Lancang, and Jinsha rivers in the SE Tibetan plateau margin. Analyses of the fractal dimensions of these river networks indicate that two tectonic deformation phases significantly controlled regional landscape development and its unique drainage features. The numerical simulations depict the river networks to comprise very long and relatively straight stream trunks, and relatively small and short tributaries. The tectonic shortening and its accompanying rapid uplift prevented the development and lengthening of the tributaries, which might have promoted the formation of low-relief surfaces. With comparison to the digital elevation model (DEM), the fractal features of the river networks extracted from the numerical results are consistent with those extracted from the natural river networks, despite the simplicity of the numerical model. More broadly, based on the more realistic kinematic scenarios and reasonable constraints, this study contributes to the development of an effective and applicable model that can reveal important implications for the landscape evolution of the region.

Performance analysis of frequency-mixed PPP-RTK using low-cost GNSS chipset with different antenna configurations

Low-cost Global Navigation Satellite System (GNSS) devices offer a cost-effective alternative to traditional GNSS systems, making GNSS technology accessible to a wider range of applications. Nevertheless, low-cost GNSS devices often face the challenges in effectively capturing and tracking satellite signals, which leads to losing the observations at certain frequencies. Moreover, the observation peculiarities of low-cost devices are in contradistinction to those of traditional geodetic GNSS receivers. In this contribution, a low-cost PPP-RTK model that considers the unique characteristics of different types of measurements is developed and its performance is fully evaluated with u-blox F9P receivers equipped with three distinctive antenna configurations: vertical dipole, microstrip patch, and helix antennas. Several static and kinematic experiments in different scenarios are conducted to verify the effectiveness of the proposed method. The results indicate that the mixed-frequency PPP-RTK model outperforms the traditional dual-frequency one with higher positioning accuracy and fixing percentage. Among the three low-cost antennas tested, the vertical dipole antenna demonstrates the best performance under static conditions and shows a comparable performance as geodetic antennas with a positioning accuracy of 0.02 m, 0.01 m and 0.07 m in the east, north, and up components, respectively. Under low-speed kinematic scenarios, the helix antenna outperforms the other two with a positioning accuracy of (0.07 m, 0.07 m, 0.34 m). Furthermore, the helix antenna is also proved to be the best choice for vehicle navigation with an ambiguity fixing rate of over 95% and a positioning accuracy of (0.13 m, 0.14 m, 0.36 m).

Regional outer core kinematics from the time dependence of intense geomagnetic flux patches

Observations of the geomagnetic field by surface observatories and dedicated satellite missions such as the Swarm constellation provide constraints on the dynamics in Earth's outer core. In particular, global core flow models estimated by inversion of the radial magnetic induction equation provide an image of the circulation of the electrically conductive fluid at the top of the core. However, in these models the poloidal flow is much less robust than the toroidal core flow. Here, we infer regional outer core kinematics from the temporal variability of high-latitude intense geomagnetic flux patches. We develop an algorithm to fit anisotropic 2D-Gaussians to the shape of those flux patches in order to infer their area, amplitude and level of anisotropy. The temporal variabilities of these properties are used to quantify contraction, expansion, amplification, weakening and horizontal shear. Comparisons with idealized kinematic scenarios based on synthetic field and flow models allow to infer regional outer core kinematics. We found that some geomagnetic flux patches exhibit expansion and weakening corresponding to fluid upwellings, whereas other patches exhibit contraction and intensification corresponding to downwellings. In both cases the patches' area and amplitude relations follow hyperbolic curves. Our results show that the geomagnetic flux patches are affected by upwelling more often than by downwelling during the historical period. Equatorially symmetric poloidal flow prior to ≈1910 is inferred for the western intense patches. Kinematic scenarios where the field and flow structures centers coincide failed to reproduce the geomagnetic flux patches behavior. We recover the flux concentration efficiency of intense geomagnetic flux patches with an upwelling that resides two times its radius size away from the center of the flux patch. We also found a significant level of anisotropy over long periods for the historical geomagnetic flux patches. Anisotropic magnetic flux patches that are elongated in the direction of the shear flow may explain the east-west oriented present-day field at high latitudes of the southern Hemisphere. Overall, stretching effects at the top of the core can be deduced from our analysis of regional SV and allow further inferences on the poloidal part of the core flow.

Precise point positioning with mixed single- and dual-frequency GNSS observations from Android smartphones considering code-carrier inconsistency

The open access to raw Global Navigation Satellite System (GNSS) measurements from Android smartphones brings new possibilities to high-accuracy positioning with precise point positioning (PPP) technique. However, decimeter or even centimeter level positioning accuracy is still challengeable mainly due to the low completeness of dual-frequency observations and specific observation errors from a smartphone. Huawei P40 released in 2020 is the first module that can track multi-GNSS multi-frequency signals. Based on GNSS observations from P40 and a co-located geodetic-grade receiver, a method is proposed to extract and model the P40 code-carrier inconsistency errors. The P40 observation inconsistency presents a linear drift pattern with respect to time at each frequency and can even reach hundreds of meters. A correction model is then established which reduces the code-carrier differences to a level of few meters. Regarding to the P40 code-carrier inconsistency error signature, an uncombined precise point positioning (PPP) algorithm is developed with the inconsistency error treated with different schemes, including correction using established model, parameterization as a linear function, or estimated as an independent clock offset for carrier-phase observation. Meanwhile, to cope with the dual-frequency data deficiency of P40, the PPP algorithm is designed based on pure single-frequency processing which can handle mixed single- and dual-frequency observations. Positioning performances of three schemes are validated in both static and kinematic scenarios. With applying the code-carrier inconsistency schemes, P40 positioning precision reaches 0.2 m and 1.0 m for static and kinematic experiments, respectively, which is improved by an order of magnitude against the case without. Furthermore, precision can be even improved when P40 is equipped with an external geodetic-grade antenna. It reaches 5.8 and 18.2 cm in the static and kinematic tests, respectively, revealing improvements of 28.7% and 54.4% against the case without considering the inconsistencies, respectively. Such result is very encouraging and indicate a positioning accuracy level close to a geodetic receiver.

Modeling, refinement and evaluation of multipath mitigation based on the hemispherical map in BDS2/BDS3 relative precise positioning

Multipath is one of the critical constraints in millimeter-level BeiDou navigation satellite system (BDS) positioning. Since multipath hemispherical map (MHM) can be conducted in relatively real-time and kinematic scenarios, it has great potential in real BDS applications. However, limited studies focus on the mitigation performance and efficiency problem based on MHM with the second-generation regional system (BDS2) and third-generation global system (BDS3). In this paper, the MHM is systematically studied in BDS2/BDS3 relative precise positioning, including the issues of MHM about the modeling, refinement, and evaluation. Specifically, at first, a rigorous modeling procedure of MHM with quality control is given, where the high-precision and high-reliability multipath corrections can be obtained. Second, based on a consecutive eleven-day designed experiment, different MHM models considering the systems, satellites, and frequencies are formed and compared comprehensively. Third, the MHM models are systematically evaluated on the positioning performance, including ambiguity resolution, float solution, and fixed solution. The results show that in MHM models, the multipath corrections for low elevation angles are more significant, and the multipath effects are usually different in different directions due to the obstacles. The behaviors of MHM models are dependent on the system, satellite, and frequency types. Besides, the MHM models are relatively stable over seven consecutive days. After applying the MHM models, the success rate of ambiguity resolution can be improved in millimeter-level positioning. Approximately 7 cm improvements can be obtained for the float solution in the 3D direction. The MHM models can improve the positioning accuracy by approximately 13% for the fixed solution especially in locations where the multipath is more severe. Moreover, the unified MHM method of the previous day with quality control can replace the refined MHM method when considering the balance between accuracy and efficiency.

High-Accuracy Absolute-Position-Aided Code Phase Tracking Based on RTK/INS Deep Integration in Challenging Static Scenarios

Many multi-sensor navigation systems urgently demand accurate positioning initialization from global navigation satellite systems (GNSSs) in challenging static scenarios. However, ground blockages against line-of-sight (LOS) signal reception make it difficult for GNSS users. Steering local codes in GNSS basebands is a desirable way to correct instantaneous signal phase misalignment, efficiently gathering useful signal power and increasing positioning accuracy. Inertial navigation systems (INSs) have been used as effective complementary dead reckoning (DR) sensors for GNSS receivers in kinematic scenarios, resisting various forms of interference. However, little work has focused on whether INSs can improve GNSS receivers in static scenarios. Thus, this paper proposes an enhanced navigation system deeply integrated with low-cost INS solutions and GNSS high-accuracy carrier-based positioning. First, an absolute code phase is predicted from base station information and integrated solutions of the INS DR and real-time kinematic (RTK) results through an extended Kalman filter (EKF). Then, a numerically controlled oscillator (NCO) leverages the predicted code phase to improve the alignment between instantaneous local code phases and received ones. The proposed algorithm is realized in a vector-tracking GNSS software-defined radio (SDR). Results of the time-of-arrival (TOA) and positioning based on real-world experiments demonstrated the proposed SDR.

Constraining the 3-D Geometry of Fold-Thrust Belts Using Section Balancing vs. 3-D Interpolative Structural and Probabilistic Modeling

Quantitative uncertainty analysis, 2-D and 3-D modeling of the subsurface, as well as their visualization form the basis for decision making in exploration, nuclear waste storage and seismic hazard assessment. Methods such as cross-section balancing are well established and yield plausible kinematic scenarios. However, they are based on geological data with errors and subject to human biases. Additionally, kinematic models do not provide a quantitative measure of the uncertainty of structures at depth. New 3-D modeling approaches have emerged that use computational interpolation, which are less dependent on human biases. Probabilistic extensions enable the quantification of uncertainties for the modeled structures. However, these approaches do not provide information on the time evolution of structures. Here, we compare classical cross-section balancing (2-D, kinematic modeling) with 3-D computational modeling to pave the way towards a solution that can bridge between these approaches. We show the strengths and weaknesses of both approaches, highlighting areas where probabilistic modeling can possibly add quantitative structural uncertainty information to improve section balancing. On the other hand, we show where probabilistic modeling still falls short of being able to cover the observed geometric complexities. We ultimately discuss how a workflow that iteratively combines results of the approaches can improve structural and kinematic constraints. As an example, we use the fold-and-thrust belt of the northern Alpine Foreland, the so-called Subalpine Molasse, focusing on the Hausham Syncline (Bavaria) and adjacent areas. We take advantage of the fact that here the stratigraphy as well as the tectonic history are well constrained. We show that shortening within the syncline progressively increases from west to east, independent from structural uncertainties. Two equally viable models can explain this. First, strain in the west is accommodated underneath the syncline in a triangle zone that progressively tapers out, or second, the strain difference is accommodated in more internal units. This highlights the importance of introducing uncertainty modeling also in kinematic restorations, as it enables identifying key regions, where different hypotheses can be tested.

Jurassic true polar wander recorded by the Lhasa terrane on its northward journey from Gondwana to Eurasia

Paleomagnetic data constrain paleogeographic motion of rocks relative to the Earth's spin axis, which is a sum of plate motion relative to the mantle and true polar wander. Discerning between these effects is challenging for studies aiming to reconstruct paleo-plate motions from deformed orogenic terranes. Here, we study the paleolatitudinal drift history of the Lhasa terrane of southern Tibet that migrated from the northern Gondwana to the southern Eurasian margin between late Triassic and early Cretaceous time. Previous work identified a 180 Ma near-equatorial Lhasa latitude and assumed near-constant paleolatitudinal drift. Large-scale true polar wander at this time, however, which has been argued for in previous work, requires highly variable Lhasa plate motion rates relative to Gondwana. Here, we test whether the alternative interpretation of constant plate motion rates provides a better prediction of paleomagnetic data. To this end, we present a new paleomagnetic pole from ∼155 Ma volcanics (here dated by U/Pb zircon) of the Lhasa terrane. Our pole comprises site mean directions from 46 lavas, passes a fold test, and is supported by an extensive rock magnetic and microscopic analysis that reveals no evidence of remagnetization. Our results give an average direction of D±ΔDx=337.1°±2.6°, I±ΔIx=−13.8°±4.9°, and a corresponding paleopole position at λp=45.3°N, φp=295.3°E with K=69.8 and A95=2.5°, predicting a similar near-equatorial, paleolatitude as at 180 Ma. This paleolatitudinal standstill is consistent with predicted paleolatitudes from global APWPs that account for Jurassic TPW and assume a constant Lhasa-Gondwana (India) oceanic spreading rate of ∼8 cm/a during the 215-130 Ma opening of the Neotethys and closure of the Mesotethys oceans. Contemporaneous arc magmatism on the Lhasa terrane was previously interpreted to indicate that the Lhasa terrane was located above a subduction zone during its northward journey to Tibet: our results show that if our reconstruction is accurate, then trench migration rates also must have been ∼8 cm/a. Our results are consistent with the range of rates of global long-lived trench migration that have been reconstructed in other studies, but they are much higher than measured in most modern systems. Our results more completely document the Lhasa terrane's separation from Gondwana and provide a straightforward methodology of using paleomagnetic data to test plate kinematic scenarios, overcoming the problem of the unknown effect of true polar wander on paleomagnetic data from deformed terranes.

Investigating the Plate Kinematics of the Bay of Biscay Using Deformable Plate Tectonic Models

AbstractThe plate kinematics of the Iberian plate and their implications on the plate tectonic evolution of the Bay of Biscay during rifting and subsequent opening of the southern North Atlantic continue to be topics of scientific discussion and debate. Constrained by previous plate reconstruction, geophysical, and geological studies, deformable plate tectonic reconstructions of the Bay of Biscay‐Parentis rift system are created in this study using the GPlates software. These deformable plate models are used to investigate the kinematics of the Landes High, Le Danois High, and Ebro Block previously recognized as independent continental blocks within deformable regions. A comparison between results calculated via deformable plate models with previously published and newly presented gravity inversion crustal thickness estimates provided a good metric for delineating the most probable plate kinematic scenario for the Bay of Biscay‐Parentis system and investigating the effect of the plate kinematic scenarios on the present‐day structure. The preferred plate kinematic model implies a transtensional Bay of Biscay‐Parentis rift system from the Jurassic to Early Cretaceous, with the onset of significant crustal thinning initiating during the Late Jurassic (∼150 Ma) induced by the motion of the Landes High and its interplay with the Ebro Block. Aside from demonstrating the role of the Landes High and its suggested interplay with structural inheritance on the deformation experienced within the Bay of Biscay, the timing and orientation of regional stress directions, and the velocities induced by the preferred deformable model provide good comparisons with previously calculated subsidence rates.

Slipping\u2013rolling transitions of a body with two contact points

In this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Ionospheric VTEC and satellite DCB estimated from single-frequency BDS observations with multi-layer mapping function

The ionospheric delays and satellite differential code biases (DCBs) act as the significant error sources in the global navigation satellite system (GNSS) positioning, navigation and timing (PNT) services, and are still challenging to estimate correctly. In this study, the ionospheric vertical total electron content (VTEC) and satellite DCBs are estimated by a refining single-frequency precise point positioning (SFPPP) method based on the multi-layer ionosphere mapping function (MF), as well as the dual-frequency methods, including the carrier-to-code leveling (CCL) and dual-frequency PPP (DFPPP). The solutions isolate the ionospheric VTEC values from the slant ionospheric delay with the generalized trigonometric series function (GTSF) and precisely estimate the satellite DCB with a zero-mean condition. The SFPPP-derived VTEC estimates are validated and evaluated by comparing with the International GNSS Service (IGS) products and using ionosphere-corrected (IC) SFPPP in both static and kinematic scenarios. Using the 74 experimental stations collected from the multi-GNSS experiment (MGEX) network from January to March 2020, the results show that the VTEC estimation precision by applying the multi-layer MF is improved for the SFPPP approach. The positioning performances of the static and kinematic BDS IC SFPPP with the ionospheric correction derived from the multi-layer MF SFPPP are better when compared to the single-layer MF. The estimated BDS DCB with the SFPPP is stable and of high accuracy. The SFPPP approach with multi-layer MF is demonstrated as a promising and reliable method to retrieve the VTEC and satellite DCB with the low-cost property for the GNSS users.

Characterisation of GNSS Carrier Phase Data on a Moving Zero-Baseline in Urban and Aerial Navigation.

We present analyses of Global Navigation Satellite System (GNSS) carrier phase observations in multiple kinematic scenarios for different receiver types. Multi-GNSS observations are recorded on high sensitivity and geodetic-grade receivers operating on a moving zero-baseline by conducting terrestrial urban and aerial flight experiments. The captured data is post-processed; carrier phase residuals are computed using the double difference (DD) concept. The estimated noise levels of carrier phases are analysed with respect to different parameters. We find DD noise levels for L1 carrier phase observations in the range of 1.4–2 mm (GPS, Global Positioning System), 2.8–4.6 mm (GLONASS, Global Navigation Satellite System), and 1.5–1.7 mm (Galileo) for geodetic receiver pairs. The noise level for high sensitivity receivers is at least higher by a factor of 2. For satellites elevating above , the dominant noise process is white phase noise. For the flight experiment, the elevation dependency of the noise is well described by the exponential model, while for the terrestrial urban experiment, multipath and diffraction effects overlay; hence no elevation dependency is found. For both experiments, a carrier-to-noise density ratio (C/N) dependency for carrier phase DDs of GPS and Galileo is clearly visible with geodetic-grade receivers. In addition, C/N dependency is also visible for carrier phase DDs of GLONASS with geodetic-grade receivers for the terrestrial urban experiment.

Investigating the role of the Galicia Bank on the formation of the North West Iberian margin using deformable plate tectonic models

The kinematic evolution of the West Iberian margin during the opening of the southern North Atlantic has been of interest for several decades and provides a well-constrained environment to study and develop new concepts related to the formation of non-volcanic (magma poor) passive margins. Building upon previous rigid and deformable plate tectonic modelling studies, the aim of this work is to create deformable plate tectonic models of the West Iberian margin using previously published constraints in GPlates to investigate the role of the Galicia Bank as an independent continental ribbon during deformation of the West Iberian margin from 200 Ma to present day. A comparison of present day crustal thickness results calculated from deformable plate tectonic reconstructions with those obtained from gravity inversion has allowed the plate kinematics of the Galicia Bank relative to the Flemish Cap to be investigated. Additionally, this comparison provided detailed insights into the most probable kinematic scenarios for the Galicia Bank continental ribbon, including its impact on the deformation experienced within the Galicia Interior Basin. Two preferred kinematic models for the Galicia Bank are proposed. One that implies synchronous motion with the Flemish Cap until ~160 Ma after which the Galicia Bank begins to move southward, causing crustal thinning within the Galicia Interior Basin. The other preferred model, despite its discrepancies with gravity inversion results, implies synchronous motion of the Galicia Bank and southeastern Flemish Cap until breakup between the southeastern Newfoundland and Iberian margins initiating ~140 Ma. In addition to the deformation induced by the motion of the Galicia Bank, this study demonstrates the influence of inherited Variscan structures and their impact on rift segmentation experienced within the Galicia Interior Basin. This is inferred through attempts to discretize triangular meshes within regions of deformation in areas where inherited structures have been previously interpreted.

Initial accuracy and reliability of current BDS-3 precise positioning, velocity estimation, and time transfer (PVT)

The primary system of Chinese global BeiDou satellite system (BDS-3) was completed to provide global services on December 27, 2018; this was a key milestone in the development process for BDS in terms of its provision of global services. Therefore, this study analyzed the current performance of BDS-3, including its precise positioning, velocity estimation, and time transfer (PVT). The datasets were derived from international GNSS monitoring and assessment system (iGMAS) tracking networks and the two international time laboratories in collaboration with the International Bureau of Weights and Measures (BIPM). With respect to the positioning, the focus is on the real-time kinematic (RTK) positioning and precise point positioning (PPP) modes with static and kinematic scenarios. The results show that the mean available satellite number is 4.8 for current BDS-3 system at short baseline XIA1–XIA3. The RTK accuracy for three components is generally within cm level; the 3D mean accuracy is 8.9 mm for BDS-3 solutions. For the PPP scenarios, the convergence time is about 4 h for TP01 and BRCH stations in two scenarios. After the convergence, the horizontal positioning accuracy is better than cm level and the vertical accuracy nearly reaches the 1 dm level. With respect to kinematic scenarios, the accuracy stays at the cm level for horizontal components and dm level for the vertical component at two stations. In terms of velocity estimation, the horizontal accuracy stays at a sub-mm level, and the vertical accuracy is better than 2 mm/s in the BDS-3 scenario, even in the Arctic. In terms of time and frequency transfer, the noise level of BDS-3 time links can reach 0.096 ns for long-distances link NT01–TP02 and 0.016 ns for short-distance links TP01–TP02. Frequency stability reaches 5E–14 accuracy when the averaging time is within 10,000 s for NT01–TP02 and 1E–15 for TP01–TP02.

Experimental results of multipath behavior for GPS L1-L2 and Galileo E1-E5b in static and kinematic scenarios

Abstract Current trends like Autonomous Driving (AD) increase the need for a precise, reliable, and continuous position at high velocities. In both natural and man-made environments, Global Navigation Satellite System (GNSS) signals suffer challenges such as multipath, attenuation, or loss-of-lock. As Highway Assist and Highway Pilot are AD next steps, multipath knowledge is necessary for this typical user-case and kinematic situations. This paper presents a multipath performance analysis for GPS and Galileo satellites in static, slow, and high kinematic scenarios. The data is provided from car test-drives in both controlled and unrestricted, near-natural environments. The Code-Minus-Carrier (CMC) and cycle-slip implementations are validated with measurement data from consecutive days. Multipath statistical models based on satellite elevation are evaluated for the three investigated scenarios. Static models derived from the car setup measurements for GPS L1, L2 and Galileo E1 and E5b show a good agreement with a state-of-the-art model as well as the enhanced Galileo signals performance. Slow kinematic multipath results in a controlled environment showed an improvement for both navigation systems compared to the static measurements at the same place. This result is confirmed by static and slow kinematic multipath simulations with the same GNSS receiver. Post-processing analysis on highway measurements revealed a bigger multipath bias, compared to the open-sky static and slow kinematic measurement campaigns. Although less critical as urban or rural, this indicates the presence of multipath in this kind of environment as well. The impact of different parameters, including receiver architecture and Signal-to-noise ratio (SNR) are analyzed and discussed. Differential position (DGNSS) based on code is computed for each epoch and compared against GNSS/INS integrated position for all three measurement campaigns. The most significant 3D absolute error occurs where the greatest multipath envelope is found.

GNSS Code Multipath Mitigation by Cascading Measurement Monitoring Techniques.

Various measurement monitoring techniques are investigated to mitigate the effect of global navigation satellite systems (GNSS) code multipath through error correction, stochastic weighting of measurements and detection and exclusion (or de-weighting) of affected measurements. Following a comprehensive review of each approach, the paper focuses on detection/exclusion and detection/de-weighting techniques where several single and dual-frequency monitoring metrics are employed in a combination with time-averaging and the M of N detection strategy. A new Geometry-Free (GF) detection metric is proposed given its capability to be combined with a preceding Code-Minus-Carrier (CMC)-based error correction to reduce the number of excluded or de-weighted measurements and thus preserve the measurement geometry. Three geometry-based algorithms, namely measurement subset testing, consecutive exclusion and iterative change of measurement weights are investigated to address multipath scenarios with multiple simultaneously affected measurements. Experimental results are provided using GPS L1, L2C and L5 data collected in multipath environments for static and kinematic scenarios. For GPS L1, the proposed combined method shows more than 38% improvement over a conventional Carrier-to-Noise-density ratio (C/N0)-based Least-Squares (LS) solution in all but deep urban canyons. Lower performance was observed for L2C and L5 frequencies with a limited number of satellites in view.

Vehicle forward collision warning algorithm based on road friction

Forward collision warning/collision avoidance (FCW/CA) systems have been developed to reduce rear-end crashes. Deceleration of vehicle is always defined as a default value in many typical proposed FCW algorithms. Considering the braking acceleration is always changed when the vehicle is braking, this paper analyzed the five typical FCW algorithms and proposed a new FCW algorithm based on road friction. The model described vehicle deceleration variation during the braking process, which was used to set up an FCW algorithm based on road friction considering the lead vehicle in three different kinematic scenarios: stationary, constant motion, and decelerating. Finally, the five typical FCW algorithms and the proposed algorithm were compared by simulation experiments. The effectiveness of the proposed warning algorithm was verified. It was concluded that the proposed algorithm was effective and conformed to the actual situation than the five FCW algorithms. Limitations and further studying recommendations for expansion of the paper were provided at the end of the paper.

A Fast-Running, End-to-End Concussion Risk Model for Assessment of Complex Human Head Kinematics.

An end-to-end, mechanism-based concussion risk model, linking head motion to axonal injury, has been demonstrated to predict concussion outcomes with greater sensitivity and specificity than external correlates such as peak head acceleration. The development of this model was driven by the need to more accurately translate head-worn sensor measurements into injury assessment in near-real time. The full end-to-end model is a detailed multi-scale model, composed of complex components (e.g., a human head finite element model), is computationally expensive, and requires specialized software. For practicality, this research-level model must be simplified into a standalone, fast-running algorithm that can be embedded on the microprocessor of a head-worn sensor. This article describes the development of a simplified, fast-running algorithm that delivers comparable results to those of the full end-to-end model. The dynamic axonal response of the human head finite element model to head motion is mathematically modeled using a lumped parameter system fitted to the finite element model response for a range of head motions. The other component models of the full end-to-end model were similarly reduced. For the same head kinematic scenarios, the probabilities of concussion obtained from the end-to-end model and from the simplified algorithm are compared well.

Basic Simulation Environment for Highly Customized Connected and Autonomous Vehicle Kinematic Scenarios.

To enhance the reality of Connected and Autonomous Vehicles (CAVs) kinematic simulation scenarios and to guarantee the accuracy and reliability of the verification, a four-layer CAVs kinematic simulation framework, which is composed with road network layer, vehicle operating layer, uncertainties modelling layer and demonstrating layer, is proposed in this paper. Properties of the intersections are defined to describe the road network. A target position based vehicle position updating method is designed to simulate such vehicle behaviors as lane changing and turning. Vehicle kinematic models are implemented to maintain the status of the vehicles when they are moving towards the target position. Priorities for individual vehicle control are authorized for different layers. Operation mechanisms of CAVs uncertainties, which are defined as position error and communication delay in this paper, are implemented in the simulation to enhance the reality of the simulation. A simulation platform is developed based on the proposed methodology. A comparison of simulated and theoretical vehicle delay has been analyzed to prove the validity and the creditability of the platform. The scenario of rear-end collision avoidance is conducted to verify the uncertainties operating mechanisms, and a slot-based intersections (SIs) control strategy is realized and verified in the simulation platform to show the supports of the platform to CAVs kinematic simulation and verification.