Geodetic System Research Articles

Analysis of vertical reference levels in the brazilian coast: comparing local and global approaches

There is a historical search for the unification of different geodetic reference systems in order to better integrate geodetic investigations. In particular, coastal zones pose the challenge of connecting terrestrial and oceanic references when working with different vertical reference levels. This study aims to investigate the goodness-of-fit of ocean models to local observations, as well as to update and improve reference levels (RL) in two tide gauges (TGs) in Brazil (Imbituba and Fortaleza). Local RLs were connected to a global reference system (GRS80), which allowed absolute analyses using the mean sea surface (MSS) and lowest astronomical tide (LAT) models MSS_CNES_ CLS15, DTU_15_MSS, DTU_18_MSS and DTU_15_LAT. In the selected TGs, the MSS models showed a difference of centimeters in regards to the local mean sea level (MSL) defined by the Directorate of Hydrography and Navigation (DHN). Sea Surface Topography (SSTop) values were estimated from Global Geopotential Models and MSL data. The results indicated possible inconsistencies in the global model of LAT when compared to local observations, likely due to the difficulty of modeling coastal zones.

О СОХРАНЕНИИ ФОНДОВ ПРОСТРАНСТВЕННЫХ ДАННЫХ, СОЗДАННЫХ В СК-95, ПРИ ПЕРЕХОДЕ К ГСК-2011

The article gives an assessment of the measures taken in the constituent entities of the Russian Federation for the transition from CS-42 to CS-95 as one of the stages in preparation for the introduc-tion of a new state geodetic coordinate system SCS-2011. It is noted, that those subjects of the Russian Federation, where the work on the transition in the creation of spatial data necessary for the socio-economic development of the regions, from a variety of local coordinate systems (LCS) based on CS-42, to a single local coordinate system of the region, created on the basis of CS-95, has already been implemented, have advantages in the transition to SCS-2011. Such regions have the opportunity to move to SCS-2011 by establishing a connection between the unified local coordinate system of the region, based on CS-95, and SCS-2011 in the form of unified regional parameters of the orthogonal transformation.The problem of preserving the spatial data funds created in CS-95 during the transition to SCS-2011 is also considered. It is noted that for the participants of the geospatial market, law-abiding and timely (after the abolition of CS-42 and the introduction of CS-95) who converted their geodetic materials and data from CS-42 to CS-95, the problem of their preserva-tion during transition to SCS-2011 without the need for recalculation in SCS-2011. As a solution to this problem, the author proposed a new type of local coordinate system based on SCS-2011.

Monitoring the Performance of HY-2B and Jason-2/3 Sea Surface Height via the China Altimetry Calibration Cooperation Plan

Calibration and validation (Cal/Val) of the sea surface height as measured by satellite radar altimeters is essential to understand altimeter biases, observation trends, and instrument aging. It also supports the long-term stability of the produced climate change records of sea level as determined by altimetry. In this article, we report the calibration of HY-2B and Jason-2/3 using the established research infrastructure and data sharing initiative introduced by the Altimetry Calibration Cooperation Plan (ACCP) of China. Currently, three ACCP calibration sites encompass the Wanshan Islands, and two national oceanic sites are located along the China coastline. For each Cal/Val site, the components of the facilities&#x2014;the geodetic, sea level, and Global Navigation Satellite System (GNSS) infrastructure&#x2014;and the followed monitoring procedures and calibration methods are described. The HY-2B performance was primarily evaluated using about two years data, which indicated a mean bias of &#x2212;0.2 &#x00B1; 4.2 cm. Confidence in the results is strong, because the HY-2B biases were cross compared and confirmed by all the three independent sites and the three satellite ground tracks. Compared with its predecessor HY-2A, HY-2B shows very stable observations with no linear drift at present. In addition, Jason-2 and Jason-3 were mainly assessed using Qianliyan site. Our results indicate that the Jason-3 sea-surface height bias is approximately 2&#x2013;3 cm smaller than that of Jason-2 and that the long-term stability of Jason-2/3 shows no significant trend, which in good agreement with the international dedicated sites. The instrument noises of Jason-2/3 and HY-2B were estimated based on the ACCP sites. The results show that the instrument noise in the previous literature is underestimated. This was also consolidated by the result from wavenumber spectrum and global crossover point analysis. The code and Wanshan data used in these Cal/Val experiments are publicly available to facilitate further work in this domain (<uri>https://github.com/GenericAltimetryTools/CalAlti</uri>).

Свободное программное обеспечение для геодезического мониторинга Moncenter

Software packages and open source libraries are an important element in the effective development of applied science. They are also important as components of methodological and educational support for applied sciences, together with regulatory documents and educational literature. The article is de-voted to the development of an open source project for satellite geodetic monitoring of engineering structures and the natural environment. The purpose of the article is to demonstrate the algorithms implemented in the Moncenter complex, the hardware for the prototype of an autonomous and low-budget GNSS sensor. An algorithm for creating a custom single-frequency base station for geodetic monitoring is presented. The results of the first testing of the developed geodetic monitoring system are presented. The error of episodic monitoring of height stability for eight months was 11 mm.

What was the River Ister in the Time of Strabo? A Mathematical Approach

Abstract We introduce a novel method for map registration and apply it to transformation of the river Ister from Strabo’s map of the World to the current map in the World Geodetic System. This transformation leads to the surprising but convincing result that Strabo’s river Ister best coincides with the nowadays Tauernbach-Isel-Drava-Danube course and not with the Danube river what is commonly assumed. Such a result is supported by carefully designed mathematical measurements and it resolves all related controversies otherwise appearing in understanding and translation of Strabo’s original text. Based on this result, we also show that Strabo’s Suevi in the Hercynian Forest corresponds to the Slavic people in the Carpathian-Alpine basin and thus that the compact Slavic settlement was there already at the beginning of the first millennium AD.

Comparative Analysis of the Molodensky and Kotsakis Ellipsoidal Heights Transformation between Geocentric and Non-Geocentric Datums Models

The non-availability of ellipsoidal heights of local geodetic Datums has made it necessary for the application of ellipsoidal heights transformation models to the available global ellipsoidal heights to obtain their respective theoretical heights in local Datums. It is required to know the accuracy, as well as reliability of any model of interest before its application. For that reason, this study comparatively analyses the Molodensky and Kotsakis models for the transformation of ellipsoidal heights between geocentric and non-geocentric Datums to determine the reliability of the Kotsakis model. The Global Navigation Satellite System (GNSS) data of the used stations were processed in World Geodetic System 1984 (WGS84) datum to obtain their global geographic coordinates and ellipsoidal heights. The coordinates, ellipsoidal heights and the transformation parameters between WGS84 and Minna Datums were applied to the Molodensky and Kotsakis models to compute the Clarke 1880 theoretical heights of the stations. The Molodensky model was used as a reference to which the Kotsakis model ellipsoidal heights were compared to obtain the Kotsakis model ellipsoidal heights discrepancies, as well as residuals. The residuals were used to compute the Root Mean Square Error (RMSE) of the Kotsakis model. The computed RMSE, as well as reliability of the model is 1.244 m. The study concluded that the low reliability, as well as accuracy of the Kotsakis model might be as a result of the two rotation datum shift parameters in it as they are the main differences between the two models.

Updating of digital topographic maps in the new national spatial coordinate system: case Fergana valley in Uzbekistan

Abstract. The classical geodetic coordinate system (CS42) in Uzbekistan uses the Krasovsky ellipsoid. The implementation of new information technologies, such as the Global Navigation Satellite System, became the basis for the development of a new national open geocentric coordinate system. This paper describes the development of a distortion grid for transforming horizontal spatial data from the local geodetic datum CS42 to a geocentric datum WGS84 for 1:100000 scale maps of the Fergana Valley in Uzbekistan. A first version of the distortion grid file has been created for transforming between CS42 and WGS84 for the whole territory of the country. The significant influence of the longitudinal drift of the region has been confirmed. The grid was used to transform topographic maps at a scale of 1:100000 for the Fergana Valley. Changing the map datum has shifted the grid of coordinate systems by 70 m in the East and 7 m in the North.

DESIGNING OF CONTINUOUS DAM MONITORING USING GLOBAL NAVIGATION SATELLITE SYSTEMS

&amp;lt;jats:p&amp;gt;The paper presents the procedure for designing a geodetic system for continuous dam monitoring and equipment necessary for the application of the Global Navigation Satellite System (GNSS). It also points out the conditions that must be respected when choosing the position of the network points and indicates the advantages and disadvantages of this system in relation to systems based on terrestrial methods. Basically, both systems provide the data necessary to monitor dam stability. Theoretical considerations have been applied to monitoring system of Soubella earth-filled dam, in Algeria. The dam created an artificial lake with a capacity of 160,000,000 m3, providing water for irrigation in the settlement below the dam. Due to the settlement vicinity, it is planned to carry out continuous dam monitoring.&amp;lt;/jats:p&amp;gt;

Monitoring the changing seismic site response of a fast-moving rockslide (Brienz/Brinzauls, Switzerland)

SUMMARYSeismic measurements on unstable rock slopes are a complementary tool to surface displacement surveys to characterize and monitor landslides. A key parameter is seismic amplification, which tends to scale with the degree of rock mass degradation. Amplification also provides a direct measure of how the wavefield is intensified during seismic loading, eventually leading to coseismic failure. Here we present the dynamic response of the fast-moving Brienz/Brinzauls rock slope instability in Switzerland (10 $ \times $ 106 to 25 $ \times $ 106 m3), which threatens settlements and infrastructure in the area. The rockslide shows strong seismic amplification at two resonant frequencies with factors of up to 11 and wavefield polarization influenced by the local fracture network orientation. We monitored the dynamic response over a period of 30 months using ambient vibrations and regional earthquake recordings. We observed a change in wavefield polarization of up to 50°, coinciding with a rotation of the relative surface displacement vector field measured by geodetic systems, highlighting the linkage between wavefield polarization and stress field (i.e. rock mass kinematics). For the analysis of secondary, relative surface displacements, we propose a singular value filtering of the displacement field to remove the principal component of landslide motion. In addition, we found increased seismic amplification values after periods of strong precipitation, providing empirical field evidence that the local precipitation history is a key parameter for assessing the hazard of earthquake-induced slope failure.

Методика повышения точности определения координат с применением инерциальных геодезических систем

The authors consider the principle of geodetic definitions using inertial systems in the absence of signals from satellite radio navigation systems and insufficient density of the initial geodetic base. A technique of improving the coordinates’ accuracy determining using inertial geodetic systems is proposed. Compensation of these systems’ errors is performed through joint equalization of data received from the inertial system, gyrotheodolite and rangefinder. In order to test the methodology, a mathematical model of the ground object movement with an inertial geodetic system was compiled. The simulation results confirm the suitability of the developed methodology. A full-scale experiment was conducted to test the efficiency of the technique. Its results are consistent with those of the simulation. The analysis of the data obtained enables concluding that the developed technique provides an increase in the accuracy of determining coordinates using inertial geodetic systems in the absence or distortion of signals from satellite radio navigation systems and insufficient density of the initial geodetic base. That is why it can be used in operational geodetic training under conditions of autonomy.

Towards Understanding the Interconnection between Celestial Pole Motion and Earth's Magnetic Field Using Space Geodetic Techniques.

The understanding of forced temporal variations in celestial pole motion (CPM) could bring us significantly closer to meeting the accuracy goals pursued by the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), i.e., 1 mm accuracy and 0.1 mm/year stability on global scales in terms of the Earth orientation parameters. Besides astronomical forcing, CPM excitation depends on the processes in the fluid core and the core–mantle boundary. The same processes are responsible for the variations in the geomagnetic field (GMF). Several investigations were conducted during the last decade to find a possible interconnection of GMF changes with the length of day (LOD) variations. However, less attention was paid to the interdependence of the GMF changes and the CPM variations. This study uses the celestial pole offsets (CPO) time series obtained from very long baseline interferometry (VLBI) observations and data such as spherical harmonic coefficients, geomagnetic jerk, and magnetic field dipole moment from a state-of-the-art geomagnetic field model to explore the correlation between them. In this study, we use wavelet coherence analysis to compute the correspondence between the two non-stationary time series in the time–frequency domain. Our preliminary results reveal interesting common features in the CPM and GMF variations, which show the potential to improve the understanding of the GMF’s contribution to the Earth’s rotation. Special attention is given to the corresponding signal between FCN and GMF and potential time lags between geomagnetic jerks and rotational variations.

Uzbekistan's coordinate system transformation from CS42 to WGS84 using distortion grid model

Currently, a non-geocentric geodetic coordinate system introduced in 1942 (CS42), based on the Krasovsky ellipsoid and the Baltic system of normal heights introduced in 1977, is used for geodetic works in the Republic of Uzbekistan. The development of the GNSS network proposes a task of transition to a new geocentric system based on the World Geodetic System 1984 (WGS84) ellipsoid. Many software products adopt 3- or 7-parameter conversions, which can cause errors up to several meters and are not suitable for many applications. In this case, local transformations using a grid of differences between observation points with known coordinates in both datums would give the best accuracy. In this paper, we discuss various interpolation methods (Kriging, Minimum Curvature, Inverse Distance to a Power and Radial Basis Function) to solve the distortion modeling between CS42 and WGS84 systems for national datum improvement. The results show that the distortion models share a common tendency for all interpolation methods: the maximum horizontal displacements are concentrated along the West Tien Shan lineament, which is the boundary of the relief lowering. The discrepancies between the grid-based (calculated) and GPS-measured coordinates are evaluated. Statistical and spatial analysis has confirmed that for the coordinate transformation from CS42 to WGS84 and vice versa, grid-based transformation with Radial Basis Function interpolation has a high accuracy transformation. Analysis of the available data across the eastern part of the country shows that some positional distortions existed between the CS42 and WGS84 datums. For the best RBF method, the magnitude of these distortions is about 0.019–0.755 m with a standard deviation of 0.015 m.

Integration of satellite geodetic observations for regional geoid modeling using remove-compute-restore technique

Advanced satellite geodetic systems have contributed to improving knowledge on changes in global gravity fields in recent years. These systems offer profound opportunities in the determination of a high-precision, high-resolution gravimetric geoid models in data deficient regions. However, due to the absence of research competence in some regions, these conventional datasets have not been implemented to update the obsolete reference frames which have been in use in these regions. This study introduces the well-known Remove-Compute-Restore (RCR) technique in modeling a gravimetric geoid model for a large data deficient region in West Africa (Nigeria) using two sets of long and short wavelength data (a) EGM2008 (long) + Airborne gravimetric observation (AGO) dataset (short) (b) EGM2008 (long) + Terrestrial gravimetric undulation (TGU) dataset (short). This therefore resulted in obtaining two sets of resultant RCR-gravimetric details whose statistics comparative assessments are produced in the body of this work. The RCR-determined gravimetric geoid model showed a strong relationship with the observed terrestrial data. The goodness of fit for the orthometric height correlation between the computed gravimetric geoid and the terrestrial data is 97.87 %. Strong relationships between the computed model and the other height models determined from the primary data are also observed. The difference between the Flury and rummel geoid-based model and the Heiskanen and moritz model in the geoid-quasi geoid separation phase shows the importance of implementing the ‘rigorous modeling technique’ for geoid quasi-geoid separation instead of the approximation method. However, the discrepancy between both models can be overlooked in a case of low accuracy geoidal operations. The RCR-based Fast Fourier Transform (FFT), and the least squares modified stokes (LSMS) was used in the quasi-geoid determination of the study region. Using the 1-parameter fit, the modified Stokes integral (FFT(b)) outperformed the LSMS model with a root mean square (rms) difference of 0.6 cm, while the LSMS outperformed both the unmodified (FFT(a)) and the modified (FFT(b)) Stokes integral using the 4-parameter fit with a rms difference of 0.5 cm. The use of both models in this study created a better perception of the quasi-geoid differential analysis, and a more refined understanding of their interaction with the satellite based quasi geoid.

MIMO-SAR Interferometric Measurements for Structural Monitoring: Accuracy and Limitations

Terrestrial Radar Interferometry (TRI) is a measurement technique capable of measuring displacements with high temporal resolution at high accuracy. Current implementations of TRI use large and/or movable antennas for generating two-dimensional displacement maps. Multiple Input Multiple Output Synthetic Aperture Radar (MIMO-SAR) systems are an emerging alternative. As they have no moving parts, they are more easily deployable and cost-effective. These features suggest the potential usage of MIMO-SAR interferometry for structural health monitoring (SHM) supplementing classical geodetic and mechanical measurement systems. The effects impacting the performance of MIMO-SAR systems are, however, not yet sufficiently well understood for practical applications. In this paper, we present an experimental investigation of a MIMO-SAR system originally devised for automotive sensing, and assess its capabilities for deformation monitoring. The acquisitions generated for these investigations feature a 180∘ Field-of-View (FOV), distances of up to 60 m and a temporal sampling rate of up to 400 Hz. Experiments include static and dynamic setups carried out in a lab-environment and under more challenging meteorological conditions featuring sunshine, fog, and cloud-cover. The experiments highlight the capabilities and limitations of the radar, while allowing quantification of the measurement uncertainties, whose sources and impacts we discuss. We demonstrate that, under sufficiently stable meteorological conditions with humidity variations smaller than 1%, displacements as low as 25 μm can be detected reliably. Detecting displacements occurring over longer time frames is limited by the uncertainty induced by changes in the refractive index.

SNR-Based GNSS-R for Coastal Sea-Level Altimetry

Geodetic Global Navigation Satellite System reflectometry (GNSS-R) uses ground-based signals of opportunity to retrieve sea levels at an intermediate spatial scale. Geodetic GNSS-R is based on the simultaneous reception of Line-of-Sight (LoS) and its coherent GNSS sea surface reflection (non-LOS) signals. The scope of this paper is to present geodetic GNSS-R applied to sea level altimetry. Signal-to-Noise Ratio (SNR) measurements from a Commercial Off-The-Shelf (COTS) geodetic-quality GNSS station at the Haiti Coast Guard Base in Port-au-Prince is used to retrieve sea levels in the International Terrestrial Reference Frame 2014 (ITRF2014). The GNSS-R sea levels are compared with those of the OTT Radar Level Sensor (RLS) installed vertically below the GNSS antenna. The Root-Mean-Square Error (RMSE) between the geodetic GNSS-R sea levels and OTT RLS records is 3.43 cm, with a correlation of 0.96. In addition, the complex differences between the OTT RLS records and 15-min GNSS-R sea levels using Global Positioning System (GPS) and Globalnaya Navigazionnaya Sputnikovaya Sistema (or Global Navigation Satellite System; GLONASS) signals for all the eight major tidal constituents are in mm-level agreement. Therefore, geodetic GNSS-R can be used as a complementary approach to the conventional method for sea level studies in a stable terrestrial reference frame.

Strategy for Connecting to the IHRF: Case Study for the Tide Gauge of Cananeia-SP

In July 2018, IBGE launched the new heights of the Brazilian Geodetic System (BGS), the normal height, which has associated gravity. These new heights are replacing the old normal-orthometric ones, in which there was only the non-parallelism correction. The IBGE informs that the values farther from the origin, have less accuracy. This lower accuracy may interfere in the future, the connection of the local tide gauges to IHRF (International Reference Frame Height). Thus, this paper proposes the integration of the local tide gauge of Cananeia-SP to the IHRF. In order to validate the methodology, the normal, Helmert, and rigorous orthometric heights using two distinct references: the Imbituba-SC tide gauge, as the origin of the BGS and the Cananeia-SP tide gauge, as a local tide gauge to be integrated into the IHRF. Calculating the three heights through these two origins, we analyzed the discrepancies in comparison to the heights calculated by IBGE. Numerical tests indicate that there was an improvement in terms of a mean and standard deviation when using the Cananeia gauge as origin in the calculation of normal, Helmert, and rigorous heights. In the congruence analysis, the calculations indicate that the highest standard deviation is presented when using IBGE normal heights. Thus, we have a new origin that is reliable and functional, can be integrated with the IHRF, where the Helmert and rigorous orthometric heights have the best statistical results.

PERFORMANCE OF ENGINEERING SURVEYS AS AN INTEGRAL PART OF LAND AND CADASTRE WORKS IN PREPARATION OF LAND PLOTS FOR REGISTRATION IN THE BASE OF THE STATE LAND CADASTER

Performing engineering surveys is a mandatory part of the development of technical documentation on land management. Surveys allow to confirm the accuracy of the performed geodetic or topographic survey. In particular, the accuracy of determining the geodetic coordinates of the turning points of the boundaries of the land, to link the turning points of the boundaries of the land to the geodetic points of the State Geodetic Network of Ukraine. The main purpose of the article is to reflect the main components of engineering surveys as part of land cadastral works in preparation of land for registration in the database of the State Land Cadastre. The coordinate basis for land management is the State Geodetic Reference Coordinate System USK-2000, the geodetic basis for land management – points of the State Geodetic Network 1-3 classes, points of geodetic networks of compaction 4 class, 1 and 2 categories, points of the surveying network. The coordinates of the points of the State Geodetic Network of Ukraine, geodetic networks of condensing and turning points of the boundaries of geospatial objects are determined by rectangular coordinates (x, y) in the Gauss-Krueger projection in the USC-2000 coordinate system or local coordinate systems. related to the USC-2000 coordinate system. The control of the differential field of coordinate corrections when working with the use of RTK technologies is carried out at least at the two nearest points of DGM and GMZ, the coordinates of which are obtained from the administrator of the geodetic data bank. The difference in the values of the coordinates of control points should not exceed 0.1 m in cities of regional importance, 0.2 m - in other cities and towns, 0.3 m - in rural areas and 0.5 m - outside the settlements. Keywords: engineering surveys, State Geodetic Network of Ukraine, land cadastral works, coordinate system, State Land Cadastre.

Результаты калибровки альтиметрических измерений космической геодезической системы «ГЕО-ИК-2» на акватории Рыбинского водохранилища

The authors present the results of satellite altimetry measurements calibration from the space geodetic system “GEO-IK-2” in the water area of the Rybinsk reservoir, obtained through two independent methods. In the first case, the altimetry measurements were calibrated by comparing the sea surface heights with respect to the reference ellipsoid, which were calculated from radio altimeter measurements, and from the processing of ground GNSS measurements performed at the sub-satellite point at the time of passing the GEO-IK-2 spacecraft. For this, in the summer of 2020, special geodetic measurements were carried out in the water area of the Rybinsk reservoir. The GNSS receiver was mounted on the Sea Buoy, which was towed by boat to the specified sub-satellite points, the coordinates of which were predetermined from the forecast of satellite orbits. At the same time, base stations for GNSS observations were installed on the coast. The largest difference in the sea surface height does not exceed 13,9 cm. The second method is cross-calibration by radio altimeter measurements from other altimetry spacecraft. In this case, the tracks of the first and second satellites within a relatively short time interval cross one common point, at which the sea surface height is determined. For this, the Jason-3 spacecraft was selected, the track of which was crossed by the GEO-IK-2 vehicle track on September 11, 2020 over the water area of the Rybinsk Reservoir. The difference in sea surface heights was 9,6 cm.

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

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.

Processing Laser Point Cloud in Fully Mechanized Mining Face Based on DGCNN

Point cloud data can accurately and intuitively reflect the spatial relationship between the coal wall and underground fully mechanized mining equipment. However, the indirect method of point cloud feature extraction based on deep neural networks will lose some of the spatial information of the point cloud, while the direct method will lose some of the local information of the point cloud. Therefore, we propose the use of dynamic graph convolution neural network (DGCNN) to extract the geometric features of the sphere in the point cloud of the fully mechanized mining face (FMMF) in order to obtain the position of the sphere (marker) in the point cloud of the FMMF, thus providing a direct basis for the subsequent transformation of the FMMF coordinates to the national geodetic coordinates with the sphere as the intermediate medium. Firstly, we completed the production of a diversity sphere point cloud (training set) and an FMMF point cloud (test set). Secondly, we further improved the DGCNN to enhance the effect of extracting the geometric features of the sphere in the FMMF. Finally, we compared the effect of the improved DGCNN with that of PointNet and PointNet++. The results show the correctness and feasibility of using DGCNN to extract the geometric features of point clouds in the FMMF and provide a new method for the feature extraction of point clouds in the FMMF. At the same time, the results provide a direct early guarantee for analyzing the point cloud data of the FMMF under the national geodetic coordinate system in the future. This can provide an effective basis for the straightening and inclining adjustment of scraper conveyors, and it is of great significance for the transparent, unmanned, and intelligent mining of the FMMF.