scholarly journals A New Azimuth-Dependent Elevation Weight (ADEW) Model for Real-Time Deformation Monitoring in Complex Environment by Multi-GNSS

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2473 ◽  
Author(s):  
Junqiang Han ◽  
Guanwen Huang ◽  
Qin Zhang ◽  
Rui Tu ◽  
Yuan Du ◽  
...  
Keyword(s):  
Real Time ◽  
Vertical Direction ◽  
Deformation Monitoring ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Time Deformation ◽  
Gnss Receivers ◽  
Micro Deformation ◽  
Global Navigation Satellite ◽  
Multipath Errors

Global navigation satellite systems (GNSS) have provided an excellent way to monitor micro-deformation in real-time. However, at local sites where landslides frequently occur, the environment can include complex surroundings with mountains, dense vegetation, and human settlements, which can severely degrade the accuracy of positioning with the GNSS technique. In this study, we propose an azimuth-dependent elevation weight (ADEW) model using an azimuth-dependent elevation mask (ADEM) to reduce the effects of multipath errors and improve the accuracy of real-time deformation monitoring in such environments. We developed an adaptive fixed-elevation mask to serve as the outlier of low precision observations at lower elevations for the ADEM, and then, we applied the weighted phase observations into the mitigation process for the effects of multipath errors. The real numerical results indicate that the ADEM model performs better than the conventional model, and the average improvements were 18.91% and 34.93% in the horizontal and vertical direction, respectively. The ADEW model further improved upon the ADEM model results by an additional 21.9% and 29.8% in the horizontal and vertical direction, respectively. Therefore, we propose that the ADEW model can significantly mitigate the effects of multipath errors and improve the accuracy of micro-deformation monitoring via GNSS receivers.

scholarly journals Asynchronous RTK Method for Detecting the Stability of the Reference Station in GNSS Deformation Monitoring

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1320
Author(s):  
Yuan Du ◽  
Guanwen Huang ◽  
Qin Zhang ◽  
Yang Gao ◽  
Yuting Gao
Keyword(s):  
Real Time ◽  
Reference Frame ◽  
Deformation Monitoring ◽  
Global Navigation Satellite Systems ◽  
Reference Station ◽  
Monitoring Station ◽  
Landslide Monitoring ◽  
Satellite Systems ◽  
Local Reference ◽  
Global Navigation Satellite

The real-time kinematic (RTK) positioning technique of global navigation satellite systems (GNSS) has been widely used for deformation monitoring in the past several decades. The RTK technique can provide relative displacements in a local reference frame defined by a highly stable reference station. However, the traditional RTK solution does not account for reference stations that experience displacement. This presents a challenge for establishing a near real-time GNSS monitoring system, as since the displacement of a reference station can be easily misinterpreted as a sign of rapid movement at the monitoring station. In this study, based on the reference observations in different time domains, asynchronous and synchronous RTK are proposed and applied together to address this issue, providing more reliable displacement information. Using the asynchronously generated time difference of a reference frame, the proposed approach can detect whether a measured displacement has occurred in the reference or the monitoring station in the current epoch. This allows for the separation of reference station movements from monitoring station movements. The results based on both simulated and landslide monitoring data demonstrate that the proposed method can provide reliable displacement determinations, which are critical in deformation monitoring applications, such as the early warning of landslides.

scholarly journals Seamless Vehicle Positioning by Lidar-GNSS Integration: Standalone and Multi-Epoch Scenarios

2021 ◽  
Vol 13 (22) ◽  
pp. 4525
Author(s):  
Junjie Zhang ◽  
Kourosh Khoshelham ◽  
Amir Khodabandeh
Keyword(s):  
Autonomous Driving ◽  
Measurement Model ◽  
Urban Environments ◽  
Global Navigation Satellite Systems ◽  
High Definition ◽  
Satellite Systems ◽  
The Road ◽  
Gnss Receivers ◽  
Vehicle Positioning ◽  
Global Navigation Satellite

Accurate and seamless vehicle positioning is fundamental for autonomous driving tasks in urban environments, requiring the provision of high-end measuring devices. Light Detection and Ranging (lidar) sensors, together with Global Navigation Satellite Systems (GNSS) receivers, are therefore commonly found onboard modern vehicles. In this paper, we propose an integration of lidar and GNSS code measurements at the observation level via a mixed measurement model. An Extended Kalman-Filter (EKF) is implemented to capture the dynamic of the vehicle movement, and thus, to incorporate the vehicle velocity parameters into the measurement model. The lidar positioning component is realized using point cloud registration through a deep neural network, which is aided by a high definition (HD) map comprising accurately georeferenced scans of the road environments. Experiments conducted in a densely built-up environment show that, by exploiting the abundant measurements of GNSS and high accuracy of lidar, the proposed vehicle positioning approach can maintain centimeter-to meter-level accuracy for the entirety of the driving duration in urban canyons.

scholarly journals Low cost GNSS receivers in time synchronization systems

2018 ◽  
Vol 67 (1) ◽  
pp. 65-72
Author(s):  
Grzegorz Czopik ◽  
Tomasz Kraszewski
Keyword(s):  
Time Synchronization ◽  
Low Cost ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Time Frequency ◽  
Delay Times ◽  
Gnss Receivers ◽  
Frequency Counter ◽  
The One ◽  
Global Navigation Satellite

The GNSS (GNSS — Global Navigation Satellite Systems) receivers can be utilized to obtain accurate time markers. The preliminary results of the cheap GNSS receivers’ tests are presented in the paper. The one receiver’s price (including antenna) does not exceed 30 $. The studies on the use of receivers in the time synchronization systems were executed. Three identical models of receiver modules were used. The 1PPS (1PPS — 1 Pulse Per Second) signals available on the receiver’s output were used. The 1PPS’s main time characteristics were described. Delay times between different receivers 1PPS signals were measured. Measurements were taken using 1 GHz oscilloscope and precise time/frequency counter T3200U. Keywords: time synchronization, 1PPS, GNSS, GPS time

scholarly journals Linear and Nonlinear Deformation Effects in the Permanent GNSS Network of Cyprus

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1768
Author(s):  
Chris Danezis ◽  
Miltiadis Chatzinikos ◽  
Christopher Kotsakis
Keyword(s):  
Crustal Deformation ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Time Period ◽  
Position Time Series ◽  
Gnss Receivers ◽  
Linear And Nonlinear ◽  
Gnss Network ◽  
Global Navigation Satellite ◽  
Gnss Data

Permanent Global Navigation Satellite Systems (GNSS) reference stations are well established as a powerful tool for the estimation of deformation induced by man-made or physical processes. GNSS sensors are successfully used to determine positions and velocities over a specified time period, with unprecedented accuracy, promoting research in many safety-critical areas, such as geophysics and geo-tectonics, tackling problems that torment traditional equipment and providing deformation products with absolute accuracy. Cyprus, being located at the Mediterranean fault, exhibits a very interesting geodynamic regime, which has yet to be investigated thoroughly. Accordingly, this research revolves around the estimation of crustal deformation in Cyprus using GNSS receivers. CYPOS (CYprus POsitioning System), a network of seven permanent GNSS stations has been operating since 2008, under the responsibility of the Department of Lands and Surveys. The continuous flow of positioning data collected over this network, offers the required information to investigate the behavior of the crustal deformation field of Cyprus using GNSS sensors for the first time. This paper presents the results of a multi-year analysis (11/2011–01/2017) of daily GNSS data and provides inferences of linear and nonlinear deforming signals into the position time series of the network stations. Specifically, 3D station velocities and seasonal periodic displacements are jointly estimated and presented via a data stacking approach with respect to the IGb08 reference frame.

scholarly journals New GNSS tomography of the atmosphere method – proposal and testing

2012 ◽  
Vol 9 ◽  
pp. 63-76 ◽  
Author(s):  
Michal Kačmařík ◽  
Lukáš Rapant
Keyword(s):  
Water Vapour ◽  
Theoretical Concept ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Gnss Meteorology ◽  
Gnss Receivers ◽  
Tomography Method ◽  
Gnss Measurements ◽  
Global Navigation Satellite

Paper is focused on GNSS meteorology which is generally used for the determination of water vapour distribution in the atmosphere from GNSS measurements. Water vapour in the atmosphere is an important parameter which influences the state and development of the weather. At first, the paper presents basics of the GNSS meteorology and tomography of the atmosphere and subsequently introduces a new GNSS tomography method which doesn't require an extensive network of GNSS receivers, but uses only a few receivers situated in a line. After a theoretical concept describing this method and used mathematical background, the results from a real experiment are shown and discussed. Unfortunately the results indicate that presented method is not able to provide credible outputs. Possibly the main problem lies in an insufficient number of available signals from current global navigation satellite systems (GPS and GLONASS) where the improvement could be expected after the start of Galileo and Compass. Potential ways how to improve the results without increasing the number of satellites are outlined in the last section.

scholarly journals Reliable and Redundant RTK Positioning for Applications in Hard Observational Conditions

2012 ◽  
Vol 47 (1) ◽  
pp. 23-33 ◽  
Author(s):  
M. Bakuła ◽  
R. Pelc-Mieczkowska ◽  
M. Walawski
Keyword(s):  
Real Time ◽  
Computer Software ◽  
Global Navigation Satellite Systems ◽  
Advanced Technique ◽  
New Approach ◽  
Satellite Systems ◽  
The Common ◽  
Global Navigation Satellite ◽  
Forest Conditions

Reliable and Redundant RTK Positioning for Applications in Hard Observational ConditionsIt is well known that RTK (Real Time Kinematic) positioning is a very efficient technique for determination of coordinates in real time, directly on location. Although this technique has been well known since the mid-nineties of the last century, the common use of this technique developed since permanent reference GNSS (Global Navigation Satellite Systems) stations started operating as the national reference systems. Positioning in real time is very convenient for users who do not need to know any advanced technique of post-processing, especially in cases when no obstructions exist around the measured point exist. However, in practice, there are some situations when the use of RTK technique makes some difficulties, especially if the GNSS receiver has no full availability of satellites. Obstructions caused by trees, buildings, power lines etc. limit satellite availability and in consequence decrease the reliability of determined coordinates significantly. In those situations gross errors of even meters can appear in RTK positioning. In order to avoid misleading coordinates occurring we can use more than one RTK receiver simultaneously. The paper presents an approach to the RTK technology based on the simultaneous use of three different RTK receivers. Three different GNSS/RTK receivers can be set on a special mounting beam and additionally RTK positions are sent in real time to a computer. The computer software analyses not only the precision but also checks the accuracy and reliability of the RTK positions determined. Consequently, the new approach to RTK survey presented can allow obtaining reliable coordinates of centimeter accuracy even under very severe forest conditions.

scholarly journals Monitoramento estrutural em obras viárias utilizando a técnica RTK/NTRIP: Análise dos dados, desenvolvimento e implementação de um sistema de alerta posicional

2021 ◽  
Vol 10 (8) ◽  
pp. e3410816846
Author(s):  
Fabiane de Fátima Maciel ◽  
Herida dos Reis Silva ◽  
Fábio Luiz Albarici ◽  
Luciano Aparecido Barbosa ◽  
Jorge Luiz Alves Trabanco
Keyword(s):  
Real Time ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Satellite Systems ◽  
Real Time Kinematic ◽  
Global Navigation ◽  
Global Navigation Satellite

Desde a ampliação do sistema rodoviário no Brasil na década de 1930, tem-se um cenário com inúmeras obras viárias em diferentes condições de uso e segurança. Tal fato é preocupante devido à falta de monitoramento adequado em OAEs (Obras de Arte Especiais) e por quem de fato estas estruturas devem ser monitoradas. Estas estruturas estão sujeitas às ações de forças estáticas e dinâmicas, podendo causar deslocamentos e/ou deformações que se caracterizam por sua amplitude, direção e comportamento temporal. Há também processos de deteriorações, sejam por desgaste ao uso ou por solicitações naturais, levando-se ao enfraquecimento da estrutura. A incorporação de métodos de inspeção e monitoramento no comportamento estrutural em OAEs torna-se crescente devido ao alto custo de recuperação destas obras. Contudo, é necessário que haja um plano de monitoramento contínuo ou periódico, de acordo com as grandezas admissíveis de cada estrutura. A tecnologia dos GNSS (Global Navigation Satellite Systems) por meio da metodologia de levantamento RTK (Real Time Kinematic), mostrou-se capaz de oferecer suporte em tempo real no controle de deformações estruturais. Neste contexto, foi desenvolvido o SiGE (Sistema de Gerenciamento Estrutural) para monitoramento e emissão de alertas acerca de eventos previamente determinados pelo operador do sistema. Com a obtenção destes dados em tempo real, é possível avaliar a segurança da estrutura em serviço, monitorar a estrutura de forma contínua e segura e aprimorar projetos futuros com a definição de deslocamentos estruturais máximos.

Assessment of geodetic products from Multi-GNSS analyses at the Onsala site

2021 ◽  
Author(s):  
Periklis-Konstantinos Diamantidis ◽  
Grzegorz Kłopotek ◽  
Rüdiger Haas ◽  
Jan Johansson
Keyword(s):  
Global Navigation Satellite Systems ◽  
Observation Data ◽  
International Gnss Service ◽  
Satellite Systems ◽  
Triple Frequency ◽  
Software Packages ◽  
Combined Solution ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Gnss Data

<p>The dawn of Beidou and Galileo as operational Global Navigation Satellite Systems (GNSS) alongside Global Positioning System (GPS) and GLONASS as well as new features that are now present in all GNSS, such as a triple-frequency setup, create new possibilities concerning improved estimation and assessment of various geodetic products. In particular, the multi-GNSS analysis gives an access to a better sky coverage allowing for improved estimation of zenith wet delays (ZWD) and tropospheric gradients (GRD), and can be used to determine integer phase ambiguities. The Multi-GNSS Experiment (MGEX), as realised by the International GNSS Service (IGS), provides orbit, clock and observation data for all operational GNSS. To take advantage of the new capabilities that these constellations bring, space-geodetic software packages have been retrofitted with Multi-GNSS-compliant modules. Based on this, two software packages, namely GipsyX and c5++, are utilised by way of the static Precise Point Positioning (PPP) approach using six months of data, and an assessment of the derived geodetic products is carried out for several GNSS receivers located at the Onsala core site. More specifically, we perform both single-constellation and multi-GNSS data analysis using Kalman filter and least-squares methods and assess the quality of the derived station positions, ZWD and GRD. A combined solution using all GNSS constellations is carried out and the improvement with respect to station position repeatabilities is assessed for each station. Results from the two software packages are compared with respect to each other and the discrepancies are discussed. Inter-system biases, which homogenise the different time scale that each GNSS operates in, and are necessary for the multi-GNSS combination, are estimated and presented. Finally, the applied inter-system weighting and its impact on the derived geodetic products are discussed.</p>

Solar radio burst interference index dedicated to GNSS single and double frequency users

2020 ◽  
Author(s):  
Jean-Marie Chevalier ◽  
Nicolas Bergeot ◽  
Pascale Defraigne ◽  
Christophe Marque ◽  
Elisa Pinat
Keyword(s):  
Real Time ◽  
Solar Radio ◽  
Global Navigation Satellite Systems ◽  
Civil Aviation ◽  
International Gnss Service ◽  
Satellite Systems ◽  
Double Frequency ◽  
Weather Events ◽  
Gnss Measurements ◽  
Global Navigation Satellite

<p>Intense solar radio bursts (SRBs) emitted at L-band frequencies are a source of radio frequency interference for Global Navigation Satellite Systems (GNSS) by inducing a noise increase in GNSS measurements, and hence degrading the carrier-to-noise density (C/N<sub>0</sub>). Such space weather events are critical for GNSS-based applications requiring real-time high-precision positioning.</p><p>Since 2015, the Royal Observatory of Belgium (ROB) monitors in near real-time the C/N<sub>0</sub> observations from the European Permanent Network (EPN). The monitoring allows to detect accurately the general fades of C/N<sub>0</sub> due to SRBs over Europe as from 1 dB-Hz. It provides in near real-time a quantification of the GNSS signal reception fade for the L1 C/A and L2 P(Y) signals and notifies civilian single and double frequency users with a 4-level index corresponding to the potential impact on their applications. This service is part of the real-time monitoring service of the PECASUS project of the International Civil Aviation Organization (ICAO) which started end of 2019.</p><p>Results of this 5-year monitoring will be discussed, including the 3 SRBs of 2015 and 2017, together with the new developments toward a global index using the International GNSS Service (IGS) network. In addition, we will show how the SRB monitoring is sometimes interfered by GPS flex power campaigns on the satellites from blocks IIR-M and IIF, and how it is mitigated . The routine and transient GPS flex power campaigns will be presented in terms of C/N<sub>0</sub> variations for the EPN and IGS networks.</p>

Assessment of geodetic products from MGEX analyses for the Onsala site

2020 ◽  
Author(s):  
Periklis-Konstantinos Diamantidis ◽  
Grzegorz Klopotek ◽  
Rüdiger Haas
Keyword(s):  
Global Navigation Satellite Systems ◽  
Observation Data ◽  
International Gnss Service ◽  
Satellite Systems ◽  
Troposphere Gradients ◽  
Combined Solution ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Gnss Data

<div>The emergence of BeiDou and Galileo as operational Global Navigation Satellite Systems (GNSS), in addition to Global Positioning System (GPS) and GLONASS which are already in use, opens up possibilities in delivering geodetic products with higher precision. Apart from ensuring the homogeneity of the derived products, multi-GNSS analysis takes the advantage of new frequencies and an improved sky coverage. This should lead to better phase ambiguity resolution and an improved estimation of target parameters such as zenith wet delays (ZWD), troposphere gradients (GRD) and station positions. The International GNSS Service (IGS) has realised this potential by initiating the Multi-GNSS Experiment (MGEX) which provides orbit, clock and observation data for all operational GNSS. Correspondingly, the multi-technique space geodetic analysis software c5++ has been augmented with a MGEX-compliant GNSS module. Based on this new module and the Precise Point Positioning (PPP) approach using six-month of data, an assessment of the derived geodetic products is carried out for several GNSS receivers located at the Onsala core site. More specifically, we perform both single- and multi-GNSS data analysis using Kalman filter and least-squares methods and assess the quality of the derived station positions, ZWD and GRD. A combined solution using all GNSS together is carried out and the improvement with respect to station position repeatabilities is assessed for each station. Inter-system biases, which homogenise the different time scale that each GNSS operates in and are necessary for the multi-GNSS combination, are estimated and presented. Finally, the applied inter-system weighting is discussed as well as its impact on the derived geodetic products.</div>

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