This study presents a Rao-Blackwellised particle filter (RBPF)-based encoder/inertial navigation system (INS)/global navigation satellite system (GNSS) integration method for improving the navigation ...performance of an autonomous land vehicle (ALV) with wheel slipping. In contrast to traditional integration methods, the proposed integration method introduces an overall wheel slip consideration for the ALV, which greatly improves the accuracy of the velocity estimation, especially when the inertial sensor is low cost. Additionally, the proposed integrated system uses double-difference pseudorange measurements instead of single point positioning results provided by low-cost GNSS receivers, which greatly improves the accuracy of the position estimation. To verify the navigation performance of the proposed integrated system, comparisons between the states estimated by the proposed system, the EKF-based integrated system and the joint wheel-slip and motion-estimation system are provided. The results of the experiment show that the proposed integrated system has the highest accuracy in both the position estimation and the velocity estimation among the three compared systems, and can improve the navigation performance during GNSS signals outages.
The CROPOS’s ZAGR stations, one of 33 stations of the Croatian permanent GNSS (Global Navigation Satellite System) network CROPOS (Croatian Positioning System), is located in Zagreb’s city centre. ...For the first time, motion of one of the CROPOS stations (the ZAGR station) during an earthquake shake (the Zagreb 2020 ML5.5) was analysed by the PPK (Post-Processed Kinematic) method using all available GNSS signals (GPS – Global Positioning System, GLONASS – GLObalnaya NAvigatsionnaya Sputnikovaya Sistem, Galileo, Bei-Dou) and seismologically interpreted. The ZAGR station is situated about 9 km to the south-southeast of the earthquake’s epicentre. The analysis showed that the station’s movements, i.e. combined surface and building motion, during the shake was far above the noise level and enabled the assessment of the station’s kinematics: movements in the range of approx. 13 cm in direction north–south (N–S) and approx. 6 cm in direction east–west (E–W). However, movements in the vertical direction were slightly above the noise level. Even though the ZAGR station kinematic behaviour was pronounced, no permanent displacement was identified. The seismological analysis showed that the ZAGR station recorded the onset of the SV-waves on the N–S component, surface waves on the N–S (predominantly Rayleigh waves) and E–W (mainly Love waves) components. The resolution of 1 s of the results of the PPK method have enabled a thorough analysis of the ZAGR station kinematics and pointed out the usefulness of the method in earthquake observations.
CROPOS-ova (Croatian Positioning System) stanica ZAGR jedna je od 33 stanice
hrvatske permanentne mreže GNSS (Global Navigation Satellite System), a nalazi se u
središtu grada Zagreba na krovu zgrade u kojoj su smještena tri fakulteta Sveučilišta u
Zagrebu (Geodetski, Građevinski i Arhitektonski fakultet). Po prvi puta su analizirani
učinci potresa na jednu od stanica mreže CROPOS primjenom metode PPK (Post-Processed Kinematic) koristeći signale svih dostupnih globalnih navigacijskih satelitskih
sustava: GPS, GLONASS, Galileo i BeiDou – i to efekti zagrebačkog potresa ML = 5,5 iz
2020. godine na stanicu ZAGR udaljenu približno 9 km od epicentra potresa. Analiza je
pokazala da su pomaci stanice ZAGR, kao kombinirana gibanja površine i zgrade, tijekom
potresne trešnje bili daleko iznad razine šuma što je omogućilo procjenu kinematičkog
ponašanja stanice: gibanja su bila u smjeru sjever-jug u rasponu približno 13 cm i približno
6 cm u rasponu u smjeru istok-zapad. Gibanja u vertikalnom smjeru identificirana su tek
neznatno iznad razine šuma. Iako je kinematičko gibanje stanice ZAGR bilo izraženo i
jasno vidljivo, nije utvđen nikakav permanentan pomak kao posljedica potresa. Seizmološka
analiza pokazala je da je stanica ZAGR zabilježila početak SV-valova na komponenti
sjever-jug, površinske Rayleigheve valove na komponenti sjever-jug te površinske Loveove
valove na komponenti istok-zapad. Jednosekundni (1 Hz) rezultati omogućili su detaljnu
analizu kinematičkog ponašanja stanice ZAGR kao što su i ukazali na korisnost metode
PPK za određivanje učinaka potresa.
A coherent scheme of federated architecture for the ultra-tight integration of global navigation satellite system (GNSS) and MEMS (micro-electro-mechanical system) inertial measurement unit (IMU) is ...presented. Inside the receiver baseband, both the controls for code numerically controlled oscillator (NCO) and carrier NCO are designed. They are each composed of two parts, one part is derived from the navigation solutions of outer loop, and the other part is given on the basis of the channel pre-filter outputs from inner loop. Each tacking channel has two filters of cascaded structure, one is the traditional pre-filter which is used to achieve GNSS signal tracking errors, and the second one is an extractor which is constructed to extract navigation solution derivation errors from the designed NCO controls and the signal tracking errors. For the ultra-tight integration navigation filter, the receiver clock residual error model after compensating the receiver clock drift is derived in detail. Finally, semi-physical simulation environment of the proposed ultra-tight integration scheme is built and closed-loop experiment under high dynamics scenario is put forward. The simulation results show that the proposed integration scheme can stably and robustly track the GNSS signals, and can achieve accurate navigation solutions even in harsh cases.
Rise times of earthquake moment release influence the spectra of seismic waves. For example, slow fault movements in tsunami earthquakes excite larger tsunamis than expected from intensities of ...short‐period seismic waves. Here we compare amplitudes of two different atmospheric waves, long‐period internal gravity waves and short‐period acoustic waves, excited by coseismic vertical crustal movements. We observe them as coseismic ionospheric disturbances by measuring ionospheric electrons using global navigation satellite systems. Four regular megathrust earthquakes Mw 8.0–9.0 showed that the internal gravity waves become ten times stronger as the magnitude increases by one. We found that the 2010 Mentawai earthquake, a typical tsunami earthquake, excited internal gravity waves stronger than those expected by this empirical relationship. On the other hand, amplitudes of acoustic waves excited by tsunami earthquakes were normal. This suggests that slow fault ruptures excite long‐period atmospheric waves efficiently, leaving a slow earthquake signature in ionospheric disturbances.
Plain Language Summary
Rapidly moving objects excite short‐period waves, and slow objects excite long‐period waves. We confirmed this for atmospheric waves excited by vertical crustal movements associated with large earthquakes. Two kinds of atmospheric waves, long‐period internal gravity waves and short‐period acoustic waves, propagate upward hundreds of kilometers and disturb the Earth’s ionosphere. They are observed by receiving dual‐frequency microwave signals from satellites. We compared atmospheric wave amplitudes excited by ordinary earthquakes and by “tsunami” earthquakes, characterized by slow fault movements. We found that the 2010 Mentawai earthquake, a typical tsunami earthquake, excited abnormally large internal gravity waves from ionospheric observations. This is the first slow earthquake signature found in space.
Key Points
Large earthquakes excite atmospheric waves with various periods that propagate upward and disturb the ionosphere
Empirical relationship between earthquake magnitudes and amplitudes of internal gravity waves is established using satellite signals
Tsunami earthquakes, characterized by slow fault sips, are found to excite longer period atmospheric waves more efficiently
Global Navigation Satellite Systems (GNSS) are not only used in terrestrial applications, but also in Low-Earth orbit satellites and in higher altitude missions. NASA’s Magnetospheric Multiscale ...(MMS) mission has demonstrated the capabilities of existing GNSS systems to provide positioning, navigation, and timing (PNT) services in the Cis-lunar space.
The resurgence in plans by national space agencies for Lunar exploration presents a need for accurate, precise, and reliable navigation systems to ensure the safety and success of future missions.
Moreover, the increased amount of Moon missions over recent years, shows the requirement of navigation capabilities for Low Lunar orbiters, Moon landers, Moon rovers, and manned missions.
The success of Global Navigation Satellite Systems (GNSS) on Earth, presents an opportunity for the study of a potential design requirements and expected performance of a Lunar GNSS constellation.
We have approached this problem through the methodology of multi-objective optimization; numerically simulating the orbits, and using the Position Dilution of Precision (PDoP) as the figure of merit to optimize a set of 200 constellation designs and improving them gradually over 1864 generations. Over 12,000 unique constellation designs were generated with the best 10 constellations presented in this paper for consideration and further study. Compared to the literature, these 10 constellations achieved a 44% improvement in PDoP (2.73) using the same number of satellites in each constellation, and meeting the performance requirements of planned Lunar missions.
•There is an increase of Moon missions over the recent years•These missions will require reliable navigation systems to ensure their success•Earth GNSS systems can provide position, navigation, and timing in the Cislunar space•Augmentation satellite systems will be required to improve PNT accuracy on the Moon•Multi-objective optimization has been used to optimize satellite constellation design•This methodology can also be used to optimize a Lunar GNSS constellation design
In the era of intelligence, there is a huge demand for precise positioning in the fields such as automatic driving, assisted driving, and vehicles to everything. Due to the continuous and ...high-precision positioning capability, the global navigation satellite system (GNSS) has been an important foundation for large-scale location applications in open sky conditions. For land vehicle kinematic navigation, the GNSS positioning method based on Kalman filtering (KF) has also become the primary choice. However, the general state model based on velocity and acceleration in KF lacks mining and utilization of the physical laws of vehicle motion, resulting in the insufficient performance of GNSS KF positioning in urban conditions. Thus, we constructed a hybrid state model, where the vehicle kinematics are classified into non-linear and quasi-linear motions, and the corresponding velocity constraint (VC) and heading constraint (HC) models are constructed respectively. Then the reparameterization between VC-model and HC-model is derived through a strict formula, and the hybrid state model can switch adaptively by vehicle motion recognition. Field vehicle test data was collected with a low-cost GNSS receiver and processed by different methods. The test results of different observation conditions and different motions show that the hybrid state model has better positioning performance, and the root means square (RMS) errors in the occlusion condition are reduced by 15% compared with only the VC-model. Further, the test results using the public data of the Google Decimeter Challenge project also verify the effectiveness and practicability of the filtering model in vehicular positioning.
In urban environments, positioning performance of global navigation satellite system (GNSS) degrades severely due to the harsh environment, which will be improved after fused with a strap-down ...inertial navigation system (SINS). However, owing to the error accumulation, the positioning ability of GNSS/SINS integration will also decrease significantly during frequent GNSS outages. To improve the positioning accuracy, we use stereo vision to enhance the performance of GNSS/SINS integration, where GNSS and stereo vision are loosely coupled and tightly coupled with SINS under the earth-centered earth-fixed (ECEF) frame, respectively. To evaluate the positioning performance of the multi-sensor fusion system, two in-field experiments were conducted to assess the contribution of stereo vision. The results show that with the support of stereo vision and SINS, GNSS accuracy can be considerably improved by 60%~80% in complex environments, which also outperforms the GNSS/SINS integration. Besides, detailed analyses in various urban environments further demonstrate that stereo vision can significantly improve the performance of GNSS/SINS integration when a long-term GNSS anomaly occurs, but it shows no improvement for a short-term GNSS anomaly.
Precise point positioning (PPP) has been suffering from slow convergences to ambiguity-fixed solutions. It is expected that this situation can be relieved or even resolved using triple-frequency GNSS ...data. We therefore attempt an approach where uncombined triple-frequency GPS/BeiDou/Galileo/QZSS (Quasi-zenith satellite system) data are injected into PPP, whereas their raw ambiguities are mapped into the extra-wide-lane, wide-lane and narrow-lane combinations for integer-cycle resolution at a single station (i.e., PPP-AR). Once both extra-wide-lane and wide-lane ambiguities are fixed to integers, the resulting unambiguous (extra-)wide-lane carrier-phase can usually outweigh the raw pseudorange to improve the convergence of positions and narrow-lane ambiguities. We used 31 days of triple-frequency multi-GNSS data from 76 stations over the Asia Oceania regions and divided them into hourly pieces for real-time PPP-AR. We found that the positioning accuracy for the first 10 min of epochs could be improved by about 50% from 0.23, 0.18 and 0.43 m to 0.12, 0.08 and 0.27 m for the east, north and up components, respectively, once wide-lane ambiguity fixing was achieved for triple-frequency PPP. Consequently, 48% of PPP solutions could be initialized successfully with narrow-lane ambiguities resolved within 2 min, in contrast to only 26% for dual-frequency PPP. On average, 6 min of epochs were required to achieve triple-frequency PPP-AR, whereas 9 min for its dual-frequency counterpart. Of particular note, the more satellites contribute to triple-frequency PPP-AR, the faster the initializations will be; as a typical example, the mean initialization time declined to 3 min in case of 20–21 satellites. We therefore envision that only a few minutes of epochs will suffice to reliably initialize real-time PPP once all GPS, BeiDou, Galileo and QZSS constellations emitting triple-frequency signals are complete in the near future.
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