The seasonal signal determined by the Global Navigation Satellite System (GNSS), which is captured in the coordinate time series, exhibits annual and semi-annual periods. This signal is frequently ...modelled by two periodic signals with constant amplitude and phase-lag. The purpose of this study is to explore the implication of different types of geophysical events on the seasonal signal in three stages—in the time span that contains the geophysical events, before and after the geophysical event, but also the stationarity phenomena, which is analysed on approximately 200 reference stations from the EPN network since 1995. The novelty of the article is demonstrated by correlating three different types of geophysical events, such as earthquakes with a magnitude greater than 6° on the Richter scale, landslides, and volcanic activity, and analysing the variation in amplitude of the seasonal signal. The geophysical events situated within a radius of 30 km from the epicentre showed a higher seasonal value than when the timespan did not contain a geophysical event. The presence of flicker and random walk noise was computed using overlapping Hadamard variance (OHVAR) and the non-stationary behaviour of the time series of the CORS coordinates in the time frequency analysis was done using continuous wavelet transform (CWT).
•Receiver clock error at 1 μs level leads to maximum 1 mm geometrical error only.•Calculation of the elevation-dependent receiver clock error for 4 GNSS systems.•Satellite radial velocity changes ...related to the position against receiver.
The differentiation of observation equations allows for the elimination of most ofGNSS errors. The receiver clock error (bias) is eliminated by the measurements of two satellites in a single difference observation equation combination. The satellite clock error is eliminated by the observations of two receivers and its magnitude is correlated with geometric error due tothe speed of light. Motivation for this paper was commonly used erroneous statement says that the receiver's clock correction must be known at the same level as satellite’s ones. As previously stated, this is mistakenly treated as a direct derivative of the speed of light, i.e. 1 µs = 300 m, 1 ns = 30 cm etc. This paper presents the method of calculation of receiver clock bias depending on zenith angle. Hypothesis is showed in a theoretical part, where radial velocity of the satellite with relation to the receiver and error in geometric distance generated by receiver with 1 µs clock error were calculated for four different GNSS (GPS, GLONASS, Galileo and Beidou) systems. In a practical part reference station located near equator was selected and together with satellite positions of four GNSS systems, obtained from precise orbit files calculations were made. A result on the base on selected sort of data both theoretical and practical calculations were consistent. Concluding, the receiver is unblinking in relation tothe satellite, thus the receiver clock error is correlated with the satellite zenith angle and must be known within 3–4 orders of magnitude better compared to the satellite one. A novelty and innovation is proved by the fact that these kinds of calculations have never been published before. Both theoretical and practical calculation part proves that receiver clock error at 1 μs level leads to only 1 mm geometrical error and might be eliminated by the usage of precise oscillator providing this level of accuracy.
Advances in remote data acquisition techniques have contributed to the flooding of society with spatial data sets and information. Widely available spatial data sets, including digital terrain models ...(DTMs) from aerial laser scanning (ALS) data, are finding more and more new applications. The article analyses and compares the heights of the 14 highest peaks of the Polish Carpathians derived from different data sources. Global navigation satellite system (GNSS) geodetic measurements were used as reference. The comparison primarily involves ALS data, and selected peaks’ GNSS measurements carried out with Xiaomi Mi 8 smartphones were also compared. Recorded raw smartphone GNSS measurements were used for calculations in post-processing mode. Other data sources were, among others, global and local databases and models and topographic maps (modern and old). The article presents an in-depth comparison of Polish and Slovak point clouds for two peaks. The results indicate the possible use of large-area laser scanning in determining the maximum heights of mountain peaks and the need to use geodetic GNSS measurements for selected peaks. For the Polish peak of Rysy, the incorrect classification of point clouds causes its height to be overestimated. The conclusions presented in the article can be used in the dissemination of knowledge and to improve positioning methods.
Determining the correct height of mountain peaks is vital for tourism, but it is also important as a reference point for devices equipped with GPS (Global Positioning System), e.g., watches or car ...navigation systems. The peak altitude data are part of geographic and geodetic information. As more modern technologies and equipment become available, their precisions should increase. However, verification of peak heights is usually only conducted for the highest, well-known mountains—lower peaks or mountain passes are rarely verified. Therefore, this study focuses on an investigation of 12 altitude points on a section of the longest and most famous touristic trail in Poland (the Main Beskid Trail), located in the Orava–Żywiec Beskids Mts (Mountains). The aim of this research is to measure and verify the heights of the 12 selected mountain peaks, in addition to evaluating the chosen methods based on the quality of the obtained data and determining their suitability and opportunities for use in further research. Measurements were obtained at the most specific height points—on the 12 highest points of the summits. This study compares two modern measurement techniques: the global navigation satellite system (GNSS) and light detection and ranging (LiDAR). The obtained results were later compared with those widely used on the internet and in printed materials (period covered: 1884–2015). This analysis demonstrates that lesser-known objects are rarely the subject of remeasurement and significant altitude errors may occur, primarily because the heights originated from a source in the past when modern methods were not available. Our findings indicate that the heights of the peaks presented in cartographic materials are inaccurate. The assumed heights should be corrected by direct measurements using modern techniques.
To prepare the mobile application for the ongoing update of the control network, it is necessary to define detailed procedures for dealing with the points database. These procedures concern the ...determination of the methodology of making an inventory of the existing database and then the determination of the rules for updating the control network using the developed application. This part describes a practical verification of Metrica for collecting control points data and showing specific cases in the collection and sharing of such data. There were created field inspections using nine different criteria on the set of selected points. Analysis shows that a large part of the points need to be reviewed once again, and its description needs to be updated.
Global Navigation Satellite System (GNSS) are widely used in many areas of human life and activity. The proper functioning of GNSS systems depends on several factors, the most important of which is ...the correct knowledge of time. The position indirectly is based on the knowledge of the distance, which is determined based on time with the knowledge of the speed of the electromagnetic wave. Thus, proper (accurate) knowledge of time (GNSS clock stability) is a key to precise positioning. In this text, the long-term stability of the GNSS station clocks covering the years 1994-2020 was analysed. For this purpose, the corrections of the clocks at selected permanent stations were used, and their stability was determined for all years separately. Then the change of clock stability over time and the search for correlation were analysed. As the results showed, there are clearly differences between four of the type of oscillators analysed. In case of the comparison on an annual basis, no change over time was found.
The result of surveys largely depends on the accuracy and measurement technique of the control network. This research work presents the application
, dedicated for collection and navigation of ...geodetic control network points. The main goal of this study is to present the motivation, methodology, and issues with analysis of the database of vertical control points. Such analysis covers south part of Poland territory for the update of the existing set of points of the vertical control network on an ongoing basis. The application has been developed with the use of a test database of points. The status of the points was checked by means of a multi-stage analysis. The prepared database of points was verified taking into account the criteria defined by the authors. In order to optimise the scoring analysis process, two groups of criteria were distinguished: independent of each other and those whose analysis was justified only under the condition of prior verification of other criteria. Based on the analysis of the collected data, the main conclusion was the ongoing need to update the data on the matrix points. It was found that information on points is often incomplete and inaccurate, especially in terms of their horizontal position, which often prevents efficient localisation of points. One of the most significant findings was that only 55.6% of the points available in the database were identified in the field. It should be noted that despite the analysis of the state of the matrix carried out in 2019 on behalf of the GUGiK, there are still many points about which information is not fully up-to-date. It is now possible to extend the application with new attributes and validation rules and conduct updates for several types of geodetic networks. Due to the extensive character of the discussed subject, the study has been divided into two parts. The continuation of this study is the second research work, which presents the development of a mobile application for the update of the geodetic control network. It will present in detail the procedures and IT application development processes.
The aim of this study was to conduct a geospatial analysis of natural disasters occurring worldwide between 1960 and 2018. A total of 9962 disasters were considered, covering 39,953 locations. These ...phenomena were analysed in terms of frequency and number to determine changes over time and predict future trends. The data included information such as location and year of occurrence. The following natural disasters were included in the analyses: droughts, earthquakes, extreme temperatures, floods, landslides, earth mass movements, storms, and volcanic activity. The analyses were carried out across three dimensions: by continent, by number of disasters in relation to population, and in relation to the area of the continents concerned. An additional objective was to visualise the distribution of disasters by affected countries. This aspect shows the incidence of disasters by year during the period under study, with a 20-year forecast for the coming years.
Mountain peaks and their altitude have been of interest to researchers across disciplines. Measurement methods and techniques have changed and developed over the years, leading to more accurate ...measurements and, consequently, more accurate determination of peak altitudes. This research transpired due to the frequency of misstatements found in existing sources including books, maps, guidebooks and the Internet. Such inaccuracies have the potential to create controversy, especially among peak-baggers in pursuit of climbing the highest summits. The Polish Sudetes Mountains were selected for this study; 24 summits in the 14 mesoregions were measured. Measurements were obtained employing the global navigation satellite system (GNSS) and light detection and ranging (LiDAR), both modern and highly precise techniques. Moreover, to determine the accuracy of measurements, several of the summits were measured using a mobile phone as an additional method. We compare GNSS vs. LiDAR and verify the level of confidence of peak heights obtained by automatic methods from LiDAR data alone. The GNSS receiver results showed a discrepancy of approximately 10 m compared with other information sources examined. Findings indicate that the heights of peaks presented in cartographic materials are inaccurate, especially in lesser-known mountain ranges. Furthermore, among all the mountain ranges examined, the results demonstrated that five of the summits were no longer classed as the highest, potentially impacting tourist perceptions and subsequent visitation. Overall, due to the topographical relief characteristics and varying vegetation cover of mountains, we argue that the re-measuring procedure should comprise two steps: (1) develop high-resolution digital elevation models (DEMs) based on LiDAR; (2) assumed heights should be measured using precise GNSS receivers. Unfortunately, due to the time constraints and the prohibitive costs of GNSS, LiDAR continues to be the most common source of new altitude data.
The aim of the work was to verify the currently available valuation approaches and algorithms, as illustrated with the example of a farming property located in the Małopolska region. The valuation of ...agricultural real estate property was carried out using the comparative approach (statistical method of market analysis, using a multiple linear regression model), then the income-based approach (investment method, by simple capitalization technique), and finally, the mixed approach (method of land index estimates). The analysis we have conducted produced varying results of the determination of value when using different valuation approaches. In the comparative and income-based approach, the values were obtained at a very similar level, which most probably results from correctly selected similar properties in both databases. The value of real estate obtained using the mixed approach turned out to be an excessively low and inadequate value compared to the values obtained in the other two approaches.
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