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GNSS Techniques for Land and Structure Monitoring

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Earth Sciences".

Deadline for manuscript submissions: closed (20 February 2022) | Viewed by 48454

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Special Issue Editors

Dr. Mirko Reguzzoni

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Geodesy and Geomatics Division, Department of Civil and Environmental Engineering, Politecnico di Milano, 20133 Milan, Italy
Interests: satellite gravimetry and gradiometry; gravity field modelling; inverse gravimetric problems
Special Issues, Collections and Topics in MDPI journals

Dr. Carlo Iapige De Gaetani

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Guest Editor

Department of Civil and Environmental Engineering (DICA), Politecnico di Milano, Italy
Interests: geomatics; building information modeling

Dr. Daniele Sampietro

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Guest Editor

Geomatics Research Department srl, 22074 Lomazzo, Italy
Interests: potential fields; gravity; inversion; geostatistics; exploration geophysics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Natural hazards due to Earth surface deformations (such as subsidence and sinking phenomena, landslides) and failure of structures (such as dams, bridges, buildings) and infrastructures (such as roads, railways, channels) necessitate prompt and efficient risk monitoring to mitigate their associated implications, such as for life safety and economic protection. Precursory changes in geometry can often reveal such risks; thus, the continuous positional determination of points with respect to time is one of the possible approaches that can be effectively used to prevent damage. These time series can be used to implement an effective maintenance plan for land, and for structures and infrastructures, and to provide prompt alarms when necessary. In this respect, the use of geodetic techniques and, in particular, of global navigation satellite systems (GNSS), as well as their integration with other types of sensors, is common practice. In recent years, the attention of the GNSS community has been drawn to the possible application of low-cost GNSS receivers which have proven to be capable of producing satisfactory results for monitoring purposes, overcoming previous limitations of this approach due to the cost of geodetic quality receivers. Furthermore, the availability of the new Galileo system has fostered even more research in this field.

The Special Issue “GNSS Techniques for Land and Structure Monitoring” aims to present the most relevant methodological advancements in GNSS monitoring, as well as case study applications of this technology. Potential topics of the Special Issue include, but are not limited to:

Natural hazard and structure/infrastructure monitoring;
Crustal deformation and land monitoring;
GNSS network design and implementation;
Time series analysis and alarm management;
Improvements by using GNSS multiconstellation monitoring systems;
Monitoring by integrating GNSS with other techniques and/or sensors;
Low-cost GNSS monitoring systems;
Experimental tests and instrumentation assessment/comparison;
Examples of technological transfer to real-world applications.

Dr. Mirko Reguzzoni
Dr. Carlo Iapige De Gaetani
Dr. Daniele Sampietro
Guest Editors

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Keywords

GNSS
monitoring
risk management
land
structures/infrastructures
displacements/deformations
time series analysis
low-cost instrumentation
multisensor systems

Published Papers (14 papers)

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Research

20 pages, 3826 KiB

Open AccessArticle

Monitoring of Structures and Infrastructures by Low-Cost GNSS Receivers

by Stefano Caldera, Stefano Barindelli, Fernando Sansò and Livia Pardi

Appl. Sci. 2022, 12(23), 12468; https://0-doi-org.brum.beds.ac.uk/10.3390/app122312468 - 06 Dec 2022

Cited by 3 | Viewed by 2425

Abstract

This paper deals with the problem of geodetic monitoring of structures by means of permanent GNSS stations, with a focus on a specific project of monitoring a bridge by a small network of three stations. What is peculiar about this paper is that the stations used are endowed with low-cost GNSS receivers, and the data treated continuously cover a time-span of more than 4 years. The monitoring service GeoGuard, at work on the project, has proved to be reliable in terms of both hardware and software. The results display almost uniform accuracy at less than the 1 mm level for daily adjusted coordinates and at the level of ∼1–2 mm for hourly solutions. After a short review on the basics of positioning by GNSS phase observations, the error of the estimated coordinates is discussed in detail, and a procedure of warning/alarm is described. The experience in terms of hardware and software employed is then presented together with the results, which are mostly displayed in graphical form and with a few tables. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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16 pages, 10197 KiB

Open AccessArticle

GNSS-Based Dam Monitoring: The Application of a Statistical Approach for Time Series Analysis to a Case Study

by Mirko Reguzzoni, Lorenzo Rossi, Carlo Iapige De Gaetani, Stefano Caldera and Riccardo Barzaghi

Appl. Sci. 2022, 12(19), 9981; https://0-doi-org.brum.beds.ac.uk/10.3390/app12199981 - 04 Oct 2022

Cited by 8 | Viewed by 2375

Abstract

Dams are one of the most important engineering works of the current human society, and it is crucial to monitor and obtain analytical data to log their conditions, predict their behavior and, eventually, receive early warnings for planning interventions and maintenance activities. In this context, GNSS-based point displacement monitoring is nowadays a consolidated technique that is able to provide daily millimeter level accuracy, even with less sophisticated and less expensive single-frequency equipment. If properly designed, daily records of such monitoring systems produce time series that, when long enough, allow for an accurate reconstruction of the geometrical deformation of the structure, thus guiding semi-automatic early warning systems. This paper focuses on the procedure for the GNSS time series processing with a statistical approach. In particular, real-world times series collected from a dam monitoring test case are processed as an example of data filtering. A remove–restore technique based on a collocation approach is applied here. Basically, it consists of an initial deterministic modeling by polynomials and periodical components through least squares adjustment and Fourier transform, respectively, followed by a stochastic modeling based on empirical covariance estimation and a collocation approach. Filtered time series are interpreted by autoregressive models based on environmental factors such as air or water temperature and reservoir water level. Spatial analysis is finally performed by computing correlations between displacements of the monitored points, as well as by visualizing the overall structure deformation in time. Results positively validate the proposed data processing workflow, providing useful hints for the implementation of automatic early warning systems in the framework of structural monitoring based on continuous displacement measurements. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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21 pages, 6391 KiB

Open AccessArticle

Evaluation of Real-Time Kinematic Positioning and Deformation Monitoring Using Xiaomi Mi 8 Smartphone

by Shulin Zeng, Cuilin Kuang and Wenkun Yu

Appl. Sci. 2022, 12(1), 435; https://0-doi-org.brum.beds.ac.uk/10.3390/app12010435 - 03 Jan 2022

Cited by 9 | Viewed by 2120

Abstract

Modern low-cost electronic devices can achieve high precision for global navigation satellite systems (GNSSs) and related applications. Recently, the pseudo-range and carrier phase have been directly obtained from a smartphone to establish a professional-level surveying device. Although promising results have been obtained by linking to an external GNSS antenna, the real-time kinematic (RTK) positioning performance requires further improvement when using the embedded smartphone antenna. We first investigate the observation quality characteristics of the Xiaomi Mi 8 smartphone. The carrier-to-noise-density ratio of L5/E5a signals is below that of L1/E1 signals, and the cycle slip and loss of lock are severe, especially for L5/E5a signals. Therefore, we use an improved stochastic model and ambiguity-resolution strategies to improve the short-baseline RTK positioning accuracy. Experimental results show that the ambiguity fixing rate can reach approximately 90% in 3 h of observations when using the embedded antenna, while the GPS/Galileo/BDS single-frequency combination is more suitable for smartphones. On the other hand, convergence takes 10–30 min, and the RTK positioning accuracy can reach 1 and 2 cm along the horizontal and vertical directions, respectively, if ambiguity is resolved correctly. Moreover, we verify the feasibility of using a mass-produced smartphone for deformation monitoring. Results from a simulated dynamic deformation experiment indicate that a smartphone can recognise deformations as small as 2 cm. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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17 pages, 36277 KiB

Open AccessArticle

Positioning Evaluation of Single and Dual-Frequency Low-Cost GNSS Receivers Signals Using PPP and Static Relative Methods in Urban Areas

by Rosendo Romero-Andrade, Manuel E. Trejo-Soto, Alejandro Vega-Ayala, Daniel Hernández-Andrade, Jesús R. Vázquez-Ontiveros and Gopal Sharma

Appl. Sci. 2021, 11(22), 10642; https://0-doi-org.brum.beds.ac.uk/10.3390/app112210642 - 11 Nov 2021

Cited by 9 | Viewed by 2382

Abstract

A positional accuracy obtained by the Precise Point Positioning and static relative methods was compared and analyzed. Test data was collected using low-cost GNSS receivers of single- and dual-frequency in urban areas. The data was analyzed for quality using the TEQC program to determine the degree of affectation of the signal in the urban area. Low-cost GNSS receivers were found to be sensitive to the multipath effect, which impacts positioning. The horizontal and vertical accuracy was evaluated with respect to Mexican regulations for the GNSS establishment criteria. Probable Error Circle (CEP) and Vertical Positioning Accuracy (EPV) were performed on low cost GNSS receiver observation data. The results show that low-cost dual-frequency GNSS receivers can be used in urban areas. The precision was obtained in the order of 0.013 m in the static relative method. The results obtained are comparable to a geodetic receiver in a geodetic baseline of <20 km. The study does not recommend using single and dual frequencies low cost GNSS receivers based on results obtained by the Precise Point Positioning (PPP) method in urban areas. The inclusion of the GGM10 model reduces the vertical precision obtained by using low cost GNSS receivers in both methods, conforming to the regulations only in the horizontal component. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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12 pages, 5969 KiB

Open AccessArticle

Comparison Analysis on the Accuracy of Galileo PPP Using Different Frequency Combinations in Europe

by Jia Song and Lewen Zhao

Appl. Sci. 2021, 11(21), 10020; https://0-doi-org.brum.beds.ac.uk/10.3390/app112110020 - 26 Oct 2021

Cited by 2 | Viewed by 1591

Abstract

The Galileo constellations are characterized by transmitting GNSS signals on multi-frequencies, which can benefit the robustness and accuracy of the solutions. However, the dual-frequency E1/E5a combinations are generally used for precise point positioning (PPP). In this paper, the performance of Galileo static and kinematic PPP using different dual- and multi-frequency combinations are assessed using observations from the European region. Overall, the accuracy of daily PPP achieved by the dual-frequency GPS, Galileo, and BDS is better than 5 mm in the horizontal direction and better than 10 mm in the vertical direction. Though the number of observed Galileo satellites is less than GPS, the horizontal accuracy can reach 1.6 mm/2.3 mm/5.7 mm on North/East/Up component, which is improved by 59.0% and 12.3% compared to the GPS in the north and up direction. Then, the accuracy of Galileo static PPP is analyzed using different dual- and multi-frequency combinations. Results indicate that the Galileo E1/E5b PPP can degrade the accuracy due to the inter-frequency clock biases between the E1/E5a and E1/E5b combinations. Best accuracy can be achieved for the triple- and four-frequency PPP, which is 4.8 mm in the up direction. The hourly accuracy for the static PPP can reach 5.6 mm/9.2 mm/12.6 mm in the north/east/up direction using the GPS/Galileo/GLONASS/BDS combinations. Finally, a positioning convergence ratio (PCR) indicator, which represents the accuracy of PPP over a period, is used to analyze the convergence time of kinematic PPP. Results indicated that the multi-frequency Galileo observations contribute minorly to the convergence of kinematic PPP. However, Galileo shows the best convergence performance for the single GNSS positioning, and the GPS/Galileo combined PPP achieved the best performance for the PPP using different GNSS combinations. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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15 pages, 5115 KiB

Open AccessArticle

Application of Multi-System Combination Precise Point Positioning in Landslide Monitoring

by Chen Lin, Guanye Wu, Xiaomin Feng, Dingxing Li, Zhichao Yu, Xuanwei Wang, Yonggang Gao, Jinyun Guo, Xiaole Wen and Wenbin Jian

Appl. Sci. 2021, 11(18), 8378; https://0-doi-org.brum.beds.ac.uk/10.3390/app11188378 - 09 Sep 2021

Cited by 10 | Viewed by 1779

Abstract

To verify the positioning performance and reliability of multi-system combination Precise Point Positioning in landslide monitoring, we carried out a multi-system combination Precise Point Positioning calculation experiment on the monitoring data of a single landslide disaster area in Fujian Province. The coordinates of the monitoring points obtained by a continuously operating reference station and the monitoring station for static relative positioning were used as reference values. The GPS system was used as the standard system and the combined PPP solution mode of G/R/C, G/R/E and G/R/E/C was used to obtain the surface displacement of the landslide area. The research showed that multi-system combination PPP converges to the centimeter level in about 30 min. The average value of internal accordant precision was more than 1 mm after convergence, and that of the external accordant precision was more than 5 cm, which meets the centimeter-level accuracy requirements in rapid landslide deformation monitoring. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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17 pages, 10168 KiB

Open AccessArticle

Sampling Rate Impact on Precise Point Positioning with a Low-Cost GNSS Receiver

by Rosendo Romero-Andrade, Manuel E. Trejo-Soto, Jesús R. Vázquez-Ontiveros, Daniel Hernández-Andrade and Juan L. Cabanillas-Zavala

Appl. Sci. 2021, 11(16), 7669; https://0-doi-org.brum.beds.ac.uk/10.3390/app11167669 - 20 Aug 2021

Cited by 14 | Viewed by 2963

Abstract

Nowadays, with the incursion of low-cost GNSS receivers with modern characteristics, it is common to investigate and apply new methodologies and solutions with different receivers of this nature. Based on this fact, the performance of the solution obtained from the low-cost GNSS receiver is evaluated compared to a geodetic grade GNSS receiver at different sampling frequencies for the PPP-static and PPP-kinematic modes. For this, the original RINEX observation files were analyzed and decimated into different sampling rates as 0.1, 0.2, 1, 5, 15 and 30 s with TEQC software. All RINEX files were submitted to the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) online service for processing with static and kinematic modes. The PPP-derived coordinates from the low-cost GNSS receiver were compared with the geodetic receiver to evaluate the obtained solution. The results reveal that the behavior of all studied sampling rates from the low-cost GNSS receiver are constant in achieved positioning. In addition, the achieved precision shows that it is recommendable to use a high sampling rate to obtain a cm level in PPP-static mode by using a low-cost GNSS receiver, this mode being the most accurate and potential alternative for structural health monitoring studies, mapping and positioning in urban areas. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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22 pages, 2850 KiB

Open AccessArticle

Performance Evaluation of Low-Cost Multi-Frequency GNSS Receivers and Antennas for Displacement Detection

by Veton Hamza, Bojan Stopar, Tomaž Ambrožič and Oskar Sterle

Appl. Sci. 2021, 11(14), 6666; https://0-doi-org.brum.beds.ac.uk/10.3390/app11146666 - 20 Jul 2021

Cited by 14 | Viewed by 3231

Abstract

Low-cost Global Navigation Satellite System (GNSS) receivers are currently used in various engineering applications. These low-cost devices are regarded as suitable sensors for applications in areas with a high risk of instrument damage. The main objectives of this research were to identify the size of displacements that can be detected in relative and absolute positioning modes by low-cost GNSS instruments and to compare the results of selected antennas. Additionally, geodetic and low-cost GNSS instruments were compared in the level of observations. For this study, low-cost SimpleRTK2B V1 boards, which house ZED-F9P GNSS chips, and three low-cost antennas, namely, Survey, Tallysman TW3882, and Survey Calibrated, were selected. While antenna calibration parameters are known for the last antenna, this is not the case for the first two. For testing purposes, a geodetic network consisting of four points was established; horizontal and vertical movements were imposed by a special mechanism with high accuracy. In relative positioning mode, the results indicate that the Survey Calibrated antenna can detect horizontal and vertical displacements with sizes of 4 mm, and 6 mm, respectively. In the detection of horizontal displacements, the performance of the Survey antenna was not as good as that of Tallysman, and the sizes of detected displacements were 6 mm and 4 mm for the first, and second antennas, respectively. Vertical displacements of 9 mm were detected using both Survey and Tallysman antennas. In absolute positioning mode, Survey Calibrated also had better performance than the Tallysman antenna, and spatial displacements of 20 mm or greater were detected by low-cost GNSS instruments. The observations made with low-cost and geodetic GNSS instruments were compared, and the latter showed better performance. However, the differences in cycle slips and the noise of phase observations were inferior. Considering their cost and proven performance, it can be concluded that such sensors can be considered for setting up a highly accurate but low-cost geodetic monitoring system. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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11 pages, 1420 KiB

Open AccessArticle

Analyzing Precision and Efficiency of Global Navigation Satellite System-Derived Height Determination for Coastal and Island Areas

by Jisun Lee, Jay Hyoun Kwon and Yong Lee

Appl. Sci. 2021, 11(11), 5310; https://0-doi-org.brum.beds.ac.uk/10.3390/app11115310 - 07 Jun 2021

Cited by 1 | Viewed by 2282

Abstract

The global navigation satellite system (GNSS)-derived height determination technique is applied in the field of surveying owing to the broad use of GNSS and the development of precise local geoid models. In Korea, this technique was officially adopted in 2020 for public surveying, such as urban facility mapping; it is also treated as an efficient way to unify the vertical datum of the inland and island areas of Korea. Here, GNSS surveying was conducted on 19 stations located in Korea’s coastal regions and islands, and GNSS-derived elevations were determined. When each GNSS-derived elevation was compared with elevations from spirit leveling, all stations showed differences of less than 3 cm when GNSS surveying was conducted for 4 h/day over two days; they were smaller than 5 cm with 2 h of surveying. These differences meet the standards of GNSS-derived elevations in Korea. In addition, GNSS-derived elevations were compared with those obtained via sea-crossing leveling in two regions, showing differences smaller than 1 cm. Sea-crossing leveling takes longer than GNSS-derived height determination, and its accuracy can be significantly affected by various environments, such as sea fog. Thus, GNSS-derived height determination represents a practical and useful technique. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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18 pages, 3895 KiB

Open AccessArticle

Performance Assessment of PPP Surveys with Open Source Software Using the GNSS GPS–GLONASS–Galileo Constellations

by Antonio Angrisano, Gino Dardanelli, Anna Innac, Alessandro Pisciotta, Claudia Pipitone and Salvatore Gaglione

Appl. Sci. 2020, 10(16), 5420; https://0-doi-org.brum.beds.ac.uk/10.3390/app10165420 - 05 Aug 2020

Cited by 20 | Viewed by 3704

Abstract

In this work, the performance of the multi-GNSS (Global Navigation Satellite System) Precise Point Positioning (PPP) technique, in static mode, is analyzed. Specifically, GPS (Global Positioning System), GLONASS, and Galileo systems are considered, and quantifying the Galileo contribution is one of the main objectives. The open source software RTKLib is adopted to process the data, with precise satellite orbits and clocks from CNES (Centre National d’Etudes Spatiales) and CLS (Collecte Localisation Satellites) analysis centers for International GNSS Service (IGS). The Iono-free model is used to correct ionospheric errors, the GOT-4.7 model is used to correct tidal effects, and Differential Code Biases (DCB) are taken from the Deutsche Forschungsanstalt für Luftund Raumfahrt (DLR) center. Two different tropospheric models are tested: Saastamoinen and Estimate ZTD (Zenith Troposhperic Delay). For the proposed study, a dataset of 31 days from a permanent GNSS station, placed in Palermo (Italy), and a dataset of 10 days from a static geodetic receiver, placed nearby the station, have been collected and processed by the most used open source software in the geomatic community. The considered GNSS configurations are seven: GPS only, GLONASS only, Galileo only, GPS+GLONASS, GPS+Galileo, GLONASS+Galileo, and GPS+GLONASS+Galileo. The results show significant performance improvement of the GNSS combinations with respect to single GNSS cases. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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22 pages, 5395 KiB

Open AccessArticle

Assessment of Static Positioning Accuracy Using Low-Cost Smartphone GPS Devices for Geodetic Survey Points’ Determination and Monitoring

by Marcin Uradziński and Mieczysław Bakuła

Appl. Sci. 2020, 10(15), 5308; https://0-doi-org.brum.beds.ac.uk/10.3390/app10155308 - 31 Jul 2020

Cited by 34 | Viewed by 6254

Abstract

Recent developments enable to access raw Global Navigation Satellite System (GNSS) measurements of mobile phones. Initially, researchers using signals gathered by mobile phones for high accuracy surveying were not successful in ambiguity fixing. Nowadays, GNSS chips, which are built in the latest smartphones, deliver code and primarily carrier phase observations available for detailed analysis in post-processing applications. Therefore, we decided to check the performance of carrier phase ambiguity fixing and positioning accuracy results of the latest Huawei P30 pro smartphone equipped with a dual-frequency GNSS receiver. We collected 3 h of raw static data in separate sessions at a known point location. For two sessions, the mobile phone was mounted vertically and for the third one—horizontally. At the same time, a high-class geodetic receiver was used for L1 and L5 signal comparison purposes. The carrier phase measurements were processed using commercial post-processing software with reference to the closest base station observations located 4 km away. Additionally, 1 h sessions were divided into 10, 15, 20 and 30 min separate sub-sessions to check the accuracy of the surveying results in fast static mode. According to the post-processing results, we were able to fix all L1 ambiguities based on Global Positioning System (GPS)-only satellite constellation. In comparison to the fixed reference point position, all three 1 h static session results were at centimeters level of accuracy (1–4 cm). For fast static surveying mode, the best results were obtained for 20 and 30 min sessions, where average accuracy was also at centimeters level. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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15 pages, 5200 KiB

Open AccessFeature PaperArticle

Modeling of the Vertical Movements of the Earth’s Crust in Poland with the Co-Kriging Method Based on Various Sources of Data

by Kamil Kowalczyk, Anna Maria Kowalczyk and Agnieszka Chojka

Appl. Sci. 2020, 10(9), 3004; https://0-doi-org.brum.beds.ac.uk/10.3390/app10093004 - 25 Apr 2020

Cited by 7 | Viewed by 2238

Abstract

The main aim of this study was to evaluate the applicability of the co-kriging method for modeling the vertical movements of the Earth’s crust based on data acquired with the use of precision leveling techniques and measurements conducted by permanent Global Navigation Satellite System (GNSS) stations. Data were processed with the use of empirical, theoretical, and directional variograms (semivariograms), as well as variogram maps. Large-scale spatial variability was determined using polynomial regression. The relationships between the length of the semi-major and semi-minor axes vs. the root mean square (RMS) and the standard error of the estimate were analyzed. The relationships between the anisotropic direction and the number of lags were determined, and other parameters were calculated. Preliminary data fitting produced non-stationary surfaces. The leveling data were anisotropic, and the GNSS data were isotropic. Nugget effects were observed in both datasets, in particular in the GNSS data. The size of the ellipse was strongly correlated with the RMS and σ (average standard deviation of prediction). The anisotropy angle was determined using the number of lags. Co-kriging was found to not be a suitable method for modeling the vertical movements of the Earth’s crust based on data from various sources. The final result was strongly influenced by the initial dataset. The obtained results show how the method of combining data sets (interpolation, network adjustment) affected the final cartographic model. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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12 pages, 3838 KiB

Open AccessArticle

Improving GNSS Landslide Monitoring with the Use of Low-Cost MEMS Accelerometers

by Alberto Cina, Ambrogio Maria Manzino and Iosif Horea Bendea

Appl. Sci. 2019, 9(23), 5075; https://0-doi-org.brum.beds.ac.uk/10.3390/app9235075 - 25 Nov 2019

Cited by 14 | Viewed by 2538

Abstract

Observation and monitoring of landslides and infrastructure is a very important basis for land planning, human activities, and safety. Geomatic techniques for deformation monitoring have usually involved GNSS and total station measurements or, more generally, expensive geodetic instruments, but other techniques, such as SAR (Synthetic Aperture Radar), can be efficiently applied. Using low-cost sensors could be an interesting alternative solution if the accuracy requirements can be satisfied. This paper shows the results obtained for tilt measurements using MEMS accelerometers, which were combined with mass-market GNSS sensors for monitoring five sites located on landslides. The use of a MEMS-like inclinometer requires an important calibration process to remove bias and improve the solution’s accuracy. In this paper, we explain the MEMS calibration procedure employed, with a simple and cheap solution. The results indicate that with a simple calibration, it is possible to improve measurement accuracy by one order of magnitude, reaching an angular accuracy of a few hundredths of a degree, verified by an independent technique. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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16 pages, 3887 KiB

Open AccessArticle

Determining the Variability of the Territorial Sea Baseline on the Example of Waterbody Adjacent to the Municipal Beach in Gdynia

by Mariusz Specht, Cezary Specht, Mariusz Wąż, Paweł Dąbrowski, Marcin Skóra and Łukasz Marchel

Appl. Sci. 2019, 9(18), 3867; https://0-doi-org.brum.beds.ac.uk/10.3390/app9183867 - 14 Sep 2019

Cited by 10 | Viewed by 9211

Abstract

The purpose of this publication is to analyze the spatial and temporal variability of the territorial sea baseline in sand bottom waterbodies, which were determined twice, in 2016 and 2018, by the Real Time Kinematic (RTK) method. This involves direct measurement of sea bottom coordinates on planned hydrographic sounding profiles using a Global Navigation Satellite System (GNSS) receiver mounted on a pole. The data were the basis for creating Digital Terrain Models (DTM), which were then used to determine the baseline for both measurement campaigns. Subsequently, terrain surface models were compared to determine bathymetry changes in the area under analysis, and an assessment was made of the baseline spatial position change over the previous two years. The measurements have shown considerable spatial and temporal variability of the baseline course along a short section of sandy beach. The territorial sea baseline was very unstable; in some places, it moved by even 20–25 m, landwards and seawards. Therefore, one can suppose that these changes are periodic, and one can conclude that the reliability of the baseline measurements can decrease quite quickly. Full article

(This article belongs to the Special Issue GNSS Techniques for Land and Structure Monitoring)

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