scholarly journals Spatio-Temporal Models for Vibration Monitoring of Elongated Structures Using Profile Laser Scans

2021 ◽  
Vol 13 (7) ◽  
pp. 1369
Author(s):  
Christoph Holst ◽  
Hans Neuner
Keyword(s):  
Harmonic Oscillation ◽  
Satellite System ◽  
Vibration Monitoring ◽  
Temporal Models ◽  
Laser Scanners ◽  
Gnss Receivers ◽  
Spatio Temporal ◽  
Set Up ◽  
General Topic ◽  
Global Navigation Satellite

Vibration monitoring is a frequent task within the general topic of Structural Health Monitoring. For this monitoring, usually accelerometers, strain gauges, fibre optic sensors or Global Navigation Satellite System (GNSS) receivers are placed on pre-selected positions on the structure and the point-wise measurements are individually processed to estimate the relevant modal parameters, for example, oscillating amplitudes and natural frequencies. If laser scanners were used for vibration monitoring, the analyses could be performed with a significantly higher spatial resolution that would be beneficial especially for locating structural weaknesses. However, to apply laser scanners rigorously to vibration monitoring, spatio-temporal models need to be set up. With this study, we develop and discuss four spatio-temporal models applied to the simulated vibration monitoring of a bridge deck. Therefore, we formulate either functional as well as stochastic connections between neighbored measurement positions within the estimation of the parameters of a harmonic oscillation. We reveal that those models allow an improved parameter estimation compared to the usually used strategies—even at lower measurement frequencies and shorter observation lengths.

Determination of global geodetic parameters based on integrated SLR measurements to LEO, geodetic, and Galileo satellites

2020 ◽  
Author(s):  
Dariusz Strugarek ◽  
Krzysztof Sośnica ◽  
Daniel Arnold ◽  
Adrian Jäggi ◽  
Grzegorz Bury ◽  
...  
Keyword(s):  
Precise Orbit Determination ◽  
Satellite System ◽  
Length Of Day ◽  
Long Baseline ◽  
Earth Rotation Parameters ◽  
Gnss Receivers ◽  
Rotation Parameters ◽  
Set Up ◽  
Global Navigation Satellite

<p>Numerous active low Earth orbiters (LEOs) and Global Navigation Satellite System (GNSS) satellites, including the Galileo constellation, are equipped with laser retroreflectors used for Satellite Laser Ranging (SLR). Moreover, most of LEOs are equipped with GNSS receivers for precise orbit determination. SLR measurements to LEOs, GNSS, and geodetic satellites vary in terms of the number of registered normal points (NPs) or registered satellite passes. In 2016-2018, SLR measurements to LEOs constituted 81% of all NPs and 59% of all registered satellite passes, whereas 10% of NPs and 30% of satellite passes, respectively, were assigned to GNSS. The remaining SLR measurements were completed by geodetic satellites, including LAGEOS-1/2, and LARES-1.</p><p>In this study, we show that the SLR observations to Galileo, passive geodetic and active LEO satellites together with precise GNSS-based orbits of LEOs and Galileo, can be used for the determination of global geodetic parameters, such as geocenter coordinates (GCC) and Earth rotation parameters (ERPs), i.e. pole coordinates, and length-of-day parameter.</p><p>GCC are typically determined using SLR observations to passive geodetic satellites, such as LAGEOS-1/2. Also, the SLR observations to LAGEOS-1/2 together with GNSS and Very Long Baseline Interferometry data are used for the determination of ERPs. Here, we use SLR observations to Galileo, LAGEOS-1/2, LARES-1, Sentinel-3A, SWARM-A/B/C, TerraSAR-X, Jason-2, GRACE-A/B satellites to investigate whether they can be applied for the reference frame realization and for deriving high-quality global geodetic parameters.</p><p>We present various types of solutions to investigate the best solution set-up. The studied solutions differ in terms of solution lengths, the combination of different sets of satellites and the relative weights for the variance scaling factors of technique and satellite-specific normal equations. We compare our results with the standard LAGEOS-based solutions, the combined EOP-14-C04 products and show the consistency of the results.</p>

scholarly journals Spatio-temporal expectile regression models

2019 ◽  
Vol 20 (4) ◽  
pp. 386-409
Author(s):  
Elmar Spiegel ◽  
Thomas Kneib ◽  
Fabian Otto-Sobotka
Keyword(s):  
Tensor Product ◽  
Least Squares Regression ◽  
Expectile Regression ◽  
Specific Distribution ◽  
Weighted Means ◽  
Temporal Models ◽  
Error Terms ◽  
Spatio Temporal ◽  
Set Up ◽  
Main Effects

Spatio-temporal models are becoming increasingly popular in recent regression research. However, they usually rely on the assumption of a specific parametric distribution for the response and/or homoscedastic error terms. In this article, we propose to apply semiparametric expectile regression to model spatio-temporal effects beyond the mean. Besides the removal of the assumption of a specific distribution and homoscedasticity, with expectile regression the whole distribution of the response can be estimated. For the use of expectiles, we interpret them as weighted means and estimate them by established tools of (penalized) least squares regression. The spatio-temporal effect is set up as an interaction between time and space either based on trivariate tensor product P-splines or the tensor product of a Gaussian Markov random field and a univariate P-spline. Importantly, the model can easily be split up into main effects and interactions to facilitate interpretation. The method is presented along the analysis of spatio-temporal variation of temperatures in Germany from 1980 to 2014.

scholarly journals GNSS Multipath Detection Using Continuous Time-Series C/N0

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4059
Author(s):  
Nobuaki Kubo ◽  
Kaito Kobayashi ◽  
Rei Furukawa
Keyword(s):  
Time Series ◽  
Continuous Time ◽  
Urban Areas ◽  
Satellite System ◽  
Line Of Sight ◽  
Static Tests ◽  
Gnss Receivers ◽  
Multipath Detection ◽  
Global Navigation Satellite ◽  
Multipath Errors

The reduction of multipath errors is a significant challenge in the Global Navigation Satellite System (GNSS), especially when receiving non-line-of-sight (NLOS) signals. However, selecting line-of-sight (LOS) satellites correctly is still a difficult task in dense urban areas, even with the latest GNSS receivers. This study demonstrates a new method of utilization of C/N0 of the GNSS to detect NLOS signals. The elevation-dependent threshold of the C/N0 setting may be effective in mitigating multipath errors. However, the C/N0 fluctuation affected by NLOS signals is quite large. If the C/N0 is over the threshold, the satellite is used for positioning even if it is still affected by the NLOS signal, which causes the positioning error to jump easily. To overcome this issue, we focused on the value of continuous time-series C/N0 for a certain period. If the C/N0 of the satellite was less than the determined threshold, the satellite was not used for positioning for a certain period, even if the C/N0 recovered over the threshold. Three static tests were conducted at challenging locations near high-rise buildings in Tokyo. The results proved that our method could substantially mitigate multipath errors in differential GNSS by appropriately removing the NLOS signals. Therefore, the performance of real-time kinematic GNSS was significantly improved.

scholarly journals Application of Least Squares with Conditional Equations Method for Railway Track Inventory Using GNSS Observations

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4948
Author(s):  
Krzysztof Czaplewski ◽  
Zbigniew Wisniewski ◽  
Cezary Specht ◽  
Andrzej Wilk ◽  
Wladyslaw Koc ◽  
...  
Keyword(s):  
Measurement Data ◽  
Satellite System ◽  
Theoretical Description ◽  
Railway Track ◽  
Land Surveying ◽  
Gnss Receivers ◽  
Mobile Satellite ◽  
Global Navigation Satellite ◽  
Gnss Observations ◽  
Observation Results

Satellite geodetic networks are commonly used in surveying tasks, but they can also be used in mobile surveys. Mobile satellite surveys can be used for trackage inventory, diagnostics and design. The combination of modern technological solutions with the adaptation of research methods known in other fields of science offers an opportunity to acquire highly accurate solutions for railway track inventory. This article presents the effects of work carried out using a mobile surveying platform on which Global Navigation Satellite System (GNSS) receivers were mounted. The satellite observations (surveys) obtained were aligned using one of the methods known from classical land surveying. The records obtained during the surveying campaign on a 246th km railway track section were subjected to alignment. This article provides a description of the surveying campaign necessary to obtain measurement data and a theoretical description of the method employed to align observation results as well as their visualisation.

scholarly journals Testing Multi-Frequency Low-Cost GNSS Receivers for Geodetic Monitoring Purposes

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4375
Author(s):  
Veton Hamza ◽  
Bojan Stopar ◽  
Tomaž Ambrožič ◽  
Goran Turk ◽  
Oskar Sterle
Keyword(s):  
Low Cost ◽  
Base Point ◽  
Satellite System ◽  
Gnss Receivers ◽  
The Difference ◽  
Short Baselines ◽  
Height Component ◽  
Global Navigation Satellite ◽  
High Level ◽  
Positional Precision

Global Navigation Satellite System (GNSS) technology is widely used for geodetic monitoring purposes. However, in cases where a higher risk of receiver damage is expected, geodetic GNSS receivers may be considered too expensive to be used. As an alternative, low-cost GNSS receivers that are cheap, light, and prove to be of adequate quality over short baselines, are considered. The main goal of this research is to evaluate the positional precision of a multi-frequency low-cost instrument, namely, ZED-F9P with u-blox ANN-MB-00 antenna, and to investigate its potential for displacement detection. We determined the positional precision within static survey, and the displacement detection within dynamic survey. In both cases, two baselines were set, with the same rover point equipped with a low-cost GNSS instrument. The base point of the first baseline was observed with a geodetic GNSS instrument, whereas the second baseline was observed with a low-cost GNSS instrument. The results from static survey for both baselines showed comparable results for horizontal components; the precision was on a level of 2 mm or better. For the height component, the results show a better performance of low-cost instruments. This may be a consequence of unknown antenna calibration parameters for low-cost GNSS antenna, while statistically significant coordinates of rover points were obtained from both baselines. The difference was again more significant in the height component. For the displacement detection, a device was used that imposes controlled movements with sub-millimeter accuracy. Results, obtained on a basis of 30-min sessions, show that low-cost GNSS instruments can detect displacements from 10 mm upwards with a high level of reliability. On the other hand, low-cost instruments performed slightly worse as far as accuracy is concerned.

scholarly journals ANALYSIS OF THE VOLUME COMPARATION OF 3’S (TS, GNSS and TLS)

2019 ◽  
Vol 94 ◽  
pp. 01014
Author(s):  
Khomsin ◽  
Danar Guruh Pratomo ◽  
Ira Mutiara Anjasmara ◽  
Faizzuddin Ahmad
Keyword(s):  
3D Model ◽  
Laser Scanner ◽  
Satellite System ◽  
Navigation Satellite ◽  
Scanner Data ◽  
Total Station ◽  
Volume Calculation ◽  
Laser Scanners ◽  
Technological Developments ◽  
Global Navigation Satellite

Recently, technological developments in the field of surveys and mapping are growing very rapidly such as total station, navigation satellite (Global Navigation Satellite System), drones and laser scanners. One application of this technology is to measure a stockpile area quickly and accurately. This research will measure two stockpiles (coal warehouses) using total station (TS), GNSS and terrestrial laser scanner (TLS). This research will compare the results of volume calculations with the data generated by 3’S (TS, GNSS and TLS). Research is conducted at Coal Yard PT. Barkalin Surabaya in Benowo District, Surabaya, East City with geographically located at 112°39'11'’ E and 7°07’13‘' S. The first step is to make 3D model of Laser Scanner data by TLS Faro 3D 120 and to do regristrastion and filltering using Faro Scene. After that the data export to be 3D model from Faro Scene format to Recap 2016 (.rcp) to present and get coordinates. The next step is to compare the coordinates from TLS, TS and GNSS RTK. Finally, the accuracy of volume calculation from TS and GNSS RTK can be compared to TLS. The volume differences between TS and TLS data are -7.31 m3 (-0.45%) for the 1st location and -6.89 m3 (-0.24%) for the 2nd location. While the volume differences between GNSS RTK and TLS are -10.34 m3 (-0.63%) and -9.05 m3 (-0.31%) for the 1st location and the 2nd location respectively. Generally, the volume differences between TLS, TS and GNSS RTK are not significant. Therefore, 3’S can be used to measure a volume of stockpile.

scholarly journals CORS ARCHITECTURE AND EVALUATION OF POSITIONING BY LOW-COST GNSS RECEIVER

2018 ◽  
Vol 44 (2) ◽  
pp. 36-44 ◽  
Author(s):  
Massimiliano Pepe
Keyword(s):  
Low Cost ◽  
Satellite System ◽  
Ease Of Use ◽  
Quality Data ◽  
Gnss Receiver ◽  
Stop And Go ◽  
Gnss Receivers ◽  
Spatial Positioning ◽  
Global Navigation Satellite

In recent years, the use of low cost GNSS receivers is becoming widespread due to their increasing performance in the spatial positioning, flexibility, ease of use and really interesting price. In addition, a recent technique of Global Navigation Satellite System (GNSS) survey, called Network Real Time Kinematic (NRTK), allows to obtain to rapid and accurate positioning measurements. The main feature of this approach is to use the raw measurements obtained and stored from a network of Continuously Operating Reference Stations (CORS) in order to generate more reliable error models that can mitigate the distance-dependent errors within the area covered by the CORS. Also, considering the huge potential of this GNSS positioning system, the purpose of this paper is to analyze and investigate the performance of the NTRK approach using a low cost GNSS receiver, in stop-and-go kinematic technique. By several case studies it was shown that, using a low cost RTK board for Arduino environment, a smartphone with open source application for Android and the availability of data correction from CORS service, a quick and accurate positioning can be obtained. Because the measures obtained in this way are quite noisy and, more in general, increasing with the baseline, by a simple and suitable statistic treatment, it was possible to increase the quality of the measure. In this way, this low cost architecture could be applied in many geomatics fields. In addition to presenting the main aspects of the NTRK infrastructure and a review of several types of correction, a general workflow in order to obtain quality data in NRTK mode, regardless of the type of GNSS receiver (multi constellations, single or many frequencies, etc.) is discussed.

scholarly journals GEOMATIC METHODS APPLIED TO THE CHANGE STUDY OF THE LA PAÚL ROCK GLACIER, SPANISH PYRENEES

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1771-1775
Author(s):  
A. Martínez-Fernández ◽  
E. Serrano ◽  
J. J. Sanjosé ◽  
M. Gómez-Lende ◽  
A. Pisabarro ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Satellite System ◽  
Ice Age ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The North ◽  
Spanish Pyrenees ◽  
Gnss Receivers ◽  
Rock Glaciers ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> Rock glaciers are one of the most important features of the mountain permafrost in the Pyrenees. La Paúl is an active rock glacier located in the north face of the Posets massif in the La Paúl glacier cirque (Spanish Pyrenees). This study presents the preliminary results of the La Paúl rock glacier monitoring works carried out through two geomatic technologies since 2013: Global Navigation Satellite System (GNSS) receivers and Terrestrial Laser Scanning (TLS) devices. Displacements measured on the rock glacier surface have demonstrated both the activity of the rock glacier and the utility of this equipment for the rock glaciers dynamic analysis. The glacier has exhibited the fastest displacements on its west side (over 35&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>), affected by the Little Ice Age, and frontal area (over 25&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>). As an indicator of permafrost in marginal environments and its peculiar morphology, La Paúl rock glacier encourages a more prolonged study and to the application of more geomatic techniques for its detailed analysis.</p>

scholarly journals RECEPTORES DE SINAIS DO SISTEMA GLOBAL DE NAVEGAÇÃO POR SATÉLITE SUBMETIDOS A INTERFERÊNCIAS FÍSICAS

2020 ◽  
Vol 35 (1) ◽  
pp. 115-125
Author(s):  
João Luiz Jacintho ◽  
Gabriel Araújo e Silva Ferraz ◽  
Lucas Santos Santana ◽  
Patrícia Ferreira Ponciano Ferraz
Keyword(s):  
Minimal Medium ◽  
Satellite System ◽  
Control Points ◽  
Satellite Navigation System ◽  
Accuracy And Precision ◽  
Agricultural Applications ◽  
Gnss Receivers ◽  
Survey Accuracy ◽  
Global Navigation Satellite ◽  
Interference Minimum

RECEPTORES DE SINAIS DO SISTEMA GLOBAL DE NAVEGAÇÃO POR SATÉLITE SUBMETIDOS A INTERFERÊNCIAS FÍSICAS   JOÃO LUIZ JACINTHO1, GABRIEL ARAÚJO E SILVA FERRAZ2, LUCAS SANTOS SANTANA3, PATRÍCIA FERREIRA PONCIANO FERRAZ4   1 Instituto Federal do Norte de Minas Gerais - IFNMG, Campus Araçuaí BR 367, km 278, s/n - Zona Rural, 39600-000, Araçuaí - MG, Brasil. [email protected]. 2 Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected]. 3Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected]. 4 Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected].   RESUMO: Incertezas são encontradas em trabalhos com receptores do Sistemas Global de Navegação por Satélite GNSS. Diante disso, objetivou-se com este estudo investigar a influência de obstáculos físicos nos erros de acurácia e precisão em levantamentos com receptores GNSS e suas aplicações agrícolas. Foram implantados quatros pontos de controle rastreados no modo estático (base) e oito pontos de estudos rastreados no modo cinemático em tempo real (RTK) e Estático Rápido (ER), utilizando um par de receptores GNSS e um par de receptores GNSS-RTK. Os níveis de acurácia e precisão foram avaliados em oito pontos obtidos por rastreios do tipo ER e RTK. Combinados com quatro bases fixas, alocados de três formas: mínima, média e alta interferência física. Pontos provenientes do levantamento RTK, apresentaram diferenças na ordem de milímetros a centímetros, quando comparados às coordenadas obtidas do levantamento (ER). Para os níveis de obstrução, a mínima interferência apresentou erro dentro dos limites estipulados pelo equipamento, a máxima interferência apresentou menor acurácia. O efeito do multipercurso do sinal foi o fator mais determinante para a redução da acurácia das coordenadas dos pontos. Recomenda-se a aplicação do levantamento RTK para trabalhos onde a precisão das coordenadas seja mais relevante que a acurácia.   Palavras-chaves: Geodésia, levantamento planialtimétrico, acurácia, precisão.   GLOBAL SATELLITE NAVIGATION SYSTEM RECEIVERS SUBMITTED TO PHYSICAL INTERFERENCES   ABSTRACT: Uncertainties are found in works with Global Navigation Satellite System receivers (GNSS). Therefore, this study aimed to investigate influence physical obstacles on accuracy and precision errors in surveys with GNSS receivers and their agricultural applications. Four control points tracked in static (base) mode and eight study points tracked in a kinematic mode in real-time (RTK) and Fast Static (ER) were implemented, using a pair of GNSS receivers and pair of GNSS-RTK receivers. Accuracy levels and precision were evaluated at eight points obtained by ER and RTK, combined with four fixed bases, allocated in three ways: minimal, medium and high physical interference. RTK survey points showed differences order millimeters to centimeters when compared to the survey (ER) coordinates. The obstruction levels, interference minimum, had an error within limits stipulated by equipment, interference maximum showed low accuracy. RTK survey is recommended for jobs where the coordinate precision is more relevant than accuracy.   Keywords: Geodesy, planialtimetric survey, accuracy, precision.

scholarly journals Towards Automatic UAS-Based Snow-Field Monitoring for Microclimate Research

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1945 ◽  
Author(s):  
Petr Gabrlik ◽  
Premysl Janata ◽  
Ludek Zalud ◽  
Josef Harcarik
Keyword(s):  
Rapid Development ◽  
Field Work ◽  
Satellite System ◽  
Mountain Range ◽  
Ground Control Points ◽  
Snow Covered Area ◽  
Covered Area ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Optimum Solution

This article presents unmanned aerial system (UAS)-based photogrammetry as an efficient method for the estimation of snow-field parameters, including snow depth, volume, and snow-covered area. Unlike similar studies employing UASs, this method benefits from the rapid development of compact, high-accuracy global navigation satellite system (GNSS) receivers. Our custom-built, multi-sensor system for UAS photogrammetry facilitates attaining centimeter- to decimeter-level object accuracy without deploying ground control points; this technique is generally known as direct georeferencing. The method was demonstrated at Mapa Republiky, a snow field located in the Krkonose, a mountain range in the Czech Republic. The location has attracted the interest of scientists due to its specific characteristics; multiple approaches to snow-field parameter estimation have thus been employed in that area to date. According to the results achieved within this study, the proposed method can be considered the optimum solution since it not only attains superior density and spatial object accuracy (approximately one decimeter) but also significantly reduces the data collection time and, above all, eliminates field work to markedly reduce the health risks associated with avalanches.

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