Hasil untuk "Geodesy"

N. Hinkley, N. Hinkley, J. Sherman et al.

Tick, Tick, Tick… Many aspects of everyday life from communication to navigation rely on the precise ticking of the microwave transitions of the atoms in atomic clocks. Optical transitions occur at much higher frequency and so offer the opportunity to reduce the scale of the ticks even more. Hinkley et al. (p. 1215, published online 22 August; see the Perspective by Margolis) compare the ticking of two optical clocks and report an instability near the 10−18 level. Such performance will improve tests of general relativity and pave the way for a redefinition of the second. An ytterbium-based optical clock exhibits a precision of nearly one part per quintillion. [Also see Perspective by Margolis] Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 1018 enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of physics beyond the standard model. Here, we describe the development and operation of two optical lattice clocks, both using spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of 1.6 × 10–18 after only 7 hours of averaging.

Luis Q. Gentner, Junyang Gou, Mohammad J. Tourian et al.

Abstract Terrestrial water storage (TWS) plays an important role in describing the Earth system, as water availability is decisive for ecosystems and human development. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) and its Follow‐On (GRACE‐FO) mission have measured TWS anomalies with unprecedented accuracy, enabling a leap in hydrological research. However, the use of the GRACE/‐FO data in climate research is restricted by the lack of measurements prior to 2002 and the 1‐yr gap between the missions. Here we present DeepRec, a deep learning approach for reconstructing GRACE‐like monthly TWS anomalies starting from 1941, covering the global land area except Greenland and Antarctica. DeepRec uses climate reanalysis variables and land use data sets as inputs to capture both natural and anthropogenic variations. Its deep learning architecture combines convolutional layers with a long short‐term memory layer to consider the spatiotemporal variations of the inputs. DeepRec quantifies the aleatoric (data) and epistemic (model) uncertainty in the TWSA estimates through a deep ensemble approach. The reconstruction achieved an area‐weighted mean basin‐scale root mean squared error (RMSE) of 17 mm against GRACE/‐FO (2002–2023) and showed improved accuracy compared to previous reconstructions when evaluated against solutions from satellite laser ranging and DORIS (weighted mean basin‐scale correlation of 0.68 for 1995–2001). Evaluations against the ERA5 water balance showed low and consistent closure errors across time periods, with weighted mean basin‐scale RMSEs of 12 mm for both 1980–2001 and 2002–2019. DeepRec achieved the lowest sea level budget closure error (RMSE of 7 mm) among all evaluated reconstructions for 1984–2001, outperforming others by 3–7 mm.

V. Pérez-Díez, I. Martí-Vidal, E. Albentosa-Ruiz et al.

Context. Compact jets from active galactic nuclei (AGN) are commonly assumed to be in equipartition between particle and magnetic-field energy densities at the regions where the radio emission dominates at centimetre wavelengths. This assumption has significant implications for both jet physics and the accuracy of VLBI-based astrometry and geodesy. Aims. We tested the validity of the energy equipartition hypothesis in AGN cores at centimetre wavelengths by analysing the blazar 1803+784 using simultaneous broadband full-polarization observations with the VLBI Global Observing System (VGOS). Methods. We present VGOS observations of the blazar 1803+784 covering the 3-11 GHz frequency range. The data were processed using a dedicated calibration pipeline, followed by model fitting and multi-frequency imaging analysis. We measured the frequency-dependent core shift and mapped the spectral index and rotation measure (RM) across the source. Results. We find a core-shift power-law index of $k_r = 0.73^{+0.12}_{-0.19}$, significantly deviating from the expected equipartition value of $k_r = 1$. This indicates that either the equipartition condition or the conical jet geometry, or both, are not fulfilled in the centimetre-wavelength core region. The wide frequency coverage of VGOS also allows us to decouple the Faraday rotation of the core into an internal component (${\rm RM}_I = 121 \pm 8$ rad m$^{-2}$, produced in the core region) and an external component (${\rm RM}_E = -44 \pm 9$ rad m$^{-2}$, associated with a distant, extended medium that may also affect the polarization in downstream regions of the jet at larger scales). Conclusions. These results demonstrate the power of VGOS for high-fidelity simultaneous multi-frequency polarimetric studies of compact AGN jets, and underline the need to account for non-equipartition effects in both jet astrophysics and geodetic VLBI.

Ivana Bogdanović Protić, Ljiljana Vasilevska, Tigran Haas et al.

This paper explores social and cultural solutions (SCS) for reclaiming public open spaces (POS) in multi-family neighborhoods, acknowledging their essential role in social, cultural, and economic development often underrealized. The research aims to identify SCS characteristics and diverse applications, while defining effective institutional, planning, and design approaches for successful POS (re)integration. Drawing on theoretical frameworks and strategic documents, alongside an analysis of best practice examples like Drewitz, Taasinge Plads, Gorica and Augustenborg, the study demonstrates how SCS enhance residential satisfaction, neighborhood perception, socio-economic status, and social inclusion. It underscores that robust resident participation is critical for initial acceptance and sustained management of POS. Furthermore, the study reveals that synergistically combining SCS with ecologically-based approaches (e.g., Nature-based Solutions, Sustainable Drainage Systems) significantly broadens these benefits, contributing to enhanced climate and social resilience, and overall sustainable urban development. This research offers actionable guidelines for practitioners to design more responsive and livable multi-family housing environments.

Matus Bakon, Ana Cláudia Teixeira, Luís Pádua et al.

Synthetic aperture radar (SAR) technology has emerged as a pivotal tool in viticulture, offering unique capabilities for various applications. This study provides a comprehensive overview of the current state-of-the-art applications of SAR in viticulture, highlighting its significance in addressing key challenges and enhancing viticultural practices. The historical evolution and motivations behind SAR technology are also provided, along with a demonstration of its applications within viticulture, showcasing its effectiveness in various aspects of vineyard management, including delineating vineyard boundaries, assessing grapevine health, and optimizing irrigation strategies. Furthermore, future perspectives and trends in SAR applications in viticulture are discussed, including advancements in SAR technology, integration with other remote sensing techniques, and the potential for enhanced data analytics and decision support systems. Through this article, a comprehensive understanding of the role of SAR in viticulture is provided, along with inspiration for future research endeavors in this rapidly evolving field, contributing to the sustainable development and optimization of vineyard management practices.

Aleksandar Nešović, Robert Kowalik, Milan Bojović et al.

The global scientific community is intensively promoting energy-plus buildings. Following the leading world trends, this paper presents a new energy-plus building concept—elevational earth-sheltered buildings with three different types of horizontal overhang photovoltaic-integrated panels: wooden support columns covered with clay tiles, steel pipes as support columns covered with sheet steel, and concrete support columns with concrete coverage. In this instance, the specific multi-numerical case study building model for the city of Kragujevac (located in central Serbia with favorable climatic conditions) was performed over 7 months (from 1 October to 30 April), taking into account the soil temperature, the effects of solar shading, the performance of the heating system—a ground source heat pump—and the characteristics of the artificial and automatic lighting control system. The simulation results show that the optimal depth of a horizontal overhang (energy-plus status) depends on the occupant’s habits, in addition to meteorological conditions. The presented methodology can be used for any other location, both in Europe and the world.

Wei Chen, Yuyu Zhou, Eleanor C. Stokes et al.

Morphological (e.g. shape, size, and height) and function (e.g. working, living, and shopping) information of buildings is highly needed for urban planning and management as well as other applications such as city-scale building energy use modeling. Due to the limited availability of socio-economic geospatial data, it is more challenging to map building functions than building morphological information, especially over large areas. In this study, we proposed an integrated framework to map building functions in 50 U.S. cities by integrating multi-source web-based geospatial data. First, a web crawler was developed to extract Points of Interest (POIs) from Tripadvisor.com, and a map crawler was developed to extract POIs and land use parcels from Google Maps. Second, an unsupervised machine learning algorithm named OneClassSVM was used to identify residential buildings based on landscape features derived from Microsoft building footprints. Third, the type ratio of POIs and the area ratio of land use parcels were used to identify six non-residential functions (i.e. hospital, hotel, school, shop, restaurant, and office). The accuracy assessment indicates that the proposed framework performed well, with an average overall accuracy of 94% and a kappa coefficient of 0.63. With the worldwide coverage of Google Maps and Tripadvisor.com, the proposed framework is transferable to other cities over the world. The data products generated from this study are of great use for quantitative city-scale urban studies, such as building energy use modeling at the single building level over large areas.

Anna Starczyk-Kołbyk

The article investigates the author’s method of estimating the final cost of a construction investment. A list of proposed methods of calculating the value of the planned final cost of the EAC investment available in the world literature was used. The modification consisted in the first place in the verification and elimination of formulas that do not match the use in construction projects and the combination of formulas resulting in the same result. The study was aimed at enabling the right choice of the method of estimating the final cost of construction investments and determining the accuracy of this estimate. It should be emphasized that the analyzed investments were annexed many times during their implementation. On the basis of the obtained results of research carried out on real construction investments, it was found that 3 methods best predict the final cost of the investment. Finally, improvements were introduced, which were analyzed, the final effect of the article is a proposal of an original, universal formula, which in each of the analyzed construction investments, regardless of the trends, deviations from the cost at the time of the inspection, forecasts the most accurate result, consistent with reality. The conducted research gives the possibility of more effective financial management of a construction investment using the corrected EAC formula in EVM method.

Lucia McCallum, David Schunck, Jamie McCallum et al.

This paper introduces a new instrument enabling a novel combination of Earth measuring techniques: direct observations with the radio astronomical instruments to satellites of the global navigation satellite systems. Inter-technique biases are a major error source in the terrestrial reference frame. Combining two major space-geodetic techniques, GNSS and VLBI, through observations to identical sensors has been considered infeasible due to their seemingly incompatible operating frequencies. The newly accessible L-band capability of the Australian VGOS telescopes is shown here, invalidating this prevailing opinion. A series of test observations demonstrates geodetic VLBI observations to GPS satellites for a continental-wide IVS telescope array, with the potential for observations at a critical scale. We anticipate immediate impact for the geodetic community, through first-ever inter-technique ties between VLBI and GNSS in the Australian region and via the opportunity for critical test observations towards the Genesis mission, geodesy's flagship project in the area of space ties set for launch in 2028.

Petar Stefanov, Hristina Prodanova, Dilyana Stefanova et al.

Karst is a widely spread natural phenomenon which provides essential benefits to human society, such as drinking water. The water cycle in the karst geosystems is the main factor for their formation and at the same time one of the main drivers for ecosystem services (ES) provision. The monitoring of the water cycle can provide valuable information regarding its functioning and ensure data for ES assessment. This paper aims to present an overview of the monitoring of the water cycle in the karst geosystems and the opportunities to integrate the monitoring data into the water regulation ES assessment. The monitoring of the water cycle is based on the methodological framework ProKARSTerra. It is applied in model karst geosystems, which are representative of the main karst types in Bulgaria. One of them is the Brestnitsa karst geosystem, which is the case study of this work. The monitoring ensures data for analyses of the water cycle which can be used in the assessment of water-related ecosystem services. The results from the analyses of the data requirements and availability show that some services such as water flow regulation and regulation of chemical condition of freshwaters can be easily provided through data for quantification, while for others further studies are needed. The results of the long-term integrated monitoring in Brestnitsa karst geosystem provide the foundation for important conclusions and models for the karst genesis and function under global changes and active anthropogenic pressure. Their integration into the assessment framework and mapping of ecosystem services is an essential step towards the development of models for sustainable use of natural resources in the karst areas.

Francisco J. Sánchez-Sesma, Francisco Luzón, Antonio García-Jerez et al.

Abstract The elastodynamic half-space Green’s function has been the subject of research for more than a century since the Lamb’s classical solution. Here, we revisit the problem and present a new closed analytical solution, in frequency domain, based upon the Principle of Equipartition (EQP) of Energy. This principle asserts that the imaginary parts of the Green’s tensor components equal the average cross-correlations of the fields generated by the uniform incidence of P and S body waves and by Rayleigh surface waves with amplitudes weighted by partition factors. The real part of the Green’s function is the Hilbert transform of the imaginary part. We validate our results by comparing synthetic seismograms of well-known solutions for surface and buried forces and discuss the implications of this new solution. Constructing synthetic diffuse fields is a first step for identifying them in nature. Graphical Abstract

Panpan Zhang, Lifeng Bao, Yange Ma et al.

One of the key goals of geodesy is to study the fine structure of the Earth’s gravity field and construct a high-resolution gravity field model (GFM). Aiming at the current insufficient resolution problem of the EIGEN_6C4 model, the refined ultra-high degree models EIGEN_3660 and EIGEN_5480 are determined with a spectral expansion approach in this study, which is to augment EIGEN_6C4 model using topographic potential models (TPMs). A comparative spectral evaluation for EIGEN_6C4, EIGEN_3660, and EIGEN_5480 models indicates that the gravity field spectral powers of EIGEN_3660 and EIGEN_5480 models outperform the EIGEN_6C4 model after degree 2000. The augmented models EIGEN_3660 and EIGEN_5480 are verified using the deflection of the vertical (DOV) of China and Colorado, gravity data from Australia and mainland America, and GNSS/leveling in China. The validation results indicate that the accuracy of EIGEN_3660 and EIGEN_5480 models in determining height anomaly, DOV, and gravity anomaly outperform the EIGEN_6C4 model, and the EIGEN_5480 model has optimal accuracy. The accuracy of EIGEN_5480 model in determining south–north component and east–west component of the DOV in China has been improved by about 21.1% and 23.1% compared to the EIGEN_6C4 model, respectively. In the mountainous Colorado, the accuracy of EIGEN_5480 model in determining south–north component and east–west component of the DOV has been improved by about 28.2% and 35.2% compared to EIGEN_6C4 model, respectively. In addition, gravity value comparison results in Australia and mainland America indicate that the accuracy of the EIGEN_5480 model for deriving gravity anomalies is improved by 16.5% and 11.3% compared to the EIGEN_6C4 model, respectively.

Zhiguo Meng, Chuanzeng Shu, Ying Yang et al.

Monitoring the surface deformation is of great significance, in order to explore the activity and geophysical features of the underground deep pressure source in the volcanic regions. In this study, the time series surface deformation of the Changbaishan volcano is retrieved via Sentinel-1B SAR data, using the SBAS-InSAR method. The main results are as follows. (1) The mean surface deformation velocity in the Changbaishan volcano is uplifted as a whole, while the uplift is locally distributed, which shows a strong correlation with faults. (2) The time series surface deformation of the Changbaishan volcano indicates an apparently seasonal change. (3) The cumulative surface deformation shows a strong correlation with the maximal magnitude and number of annual earthquakes, and it is likely dominated by the maximal magnitude of the annual earthquakes. (4) The single Mogi source model is appropriate to evaluate the deep pressure source in the Changbaishan volcano, constrained by the calculated surface deformation. The optimal estimated depth of the magma chamber is about 6.2 km, and the volume is increased by about 3.2 × 10⁶ m³. According to the time series surface deformation, it is concluded that the tectonic activity and faults, related to the deep pressure source, are pretty active in the Changbaishan volcano.

Mahdi Khoshlahjeh Azar, Siavash Shami, Faramarz Nilfouroushan et al.

Abstract Due to its proximity to Tehran, the Hashtgerd catchment in Iran is an important region that has experienced alarming subsidence rates in recent years. This study estimated the ground surface deformation in the Hashtgerd plain between 2015 and 2020 using Sentinel-1 SAR data and InSAR technique. The average LOS displacement of the ascending and descending tracks was − 23 cm/year and − 22 cm/year, respectively. The central area of the plain experienced the greatest vertical subsidence, with a more than − 100 cm cumulative displacement. The Karaj-Qazvin railway and highway that pass through this area have been damaged by subsidence, according to an analysis of profiles drawn along the transportation lines. The southern sections of Hashtgerd city have experienced a total displacement of − 30 cm/year over the course of about 6 years. The relationship between changes in groundwater level and subsidence rate in this region was examined using piezometer and precipitation data. Geoelectric sections and piezometric well logs were also utilized to investigate the geological characteristics of the Hashtgerd aquifer. According to the findings, the leading causes of subsidence were uncontrolled groundwater abstraction. This research highlights the need to comprehend the spatial distribution of confined aquifers and their effect on subsidence, which can aid in the development of a suitable management strategy to restore these aquifers.

I. van Zelst, I. van Zelst, F. Crameri et al.

<p>Geodynamic modelling provides a powerful tool to investigate processes in the Earth's crust, mantle, and core that are not directly observable. However, numerical models are inherently subject to the assumptions and simplifications on which they are based. In order to use and review numerical modelling studies appropriately, one needs to be aware of the limitations of geodynamic modelling as well as its advantages. Here, we present a comprehensive yet concise overview of the geodynamic modelling process applied to the solid Earth from the choice of governing equations to numerical methods, model setup, model interpretation, and the eventual communication of the model results. We highlight best practices and discuss their implementations including code verification, model validation, internal consistency checks, and software and data management. Thus, with this perspective, we encourage high-quality modelling studies, fair external interpretation, and sensible use of published work. We provide ample examples, from lithosphere and mantle dynamics specifically, and point out synergies with related fields such as seismology, tectonophysics, geology, mineral physics, planetary science, and geodesy. We clarify and consolidate terminology across geodynamics and numerical modelling to set a standard for clear communication of modelling studies. All in all, this paper presents the basics of geodynamic modelling for first-time and experienced modellers, collaborators, and reviewers from diverse backgrounds to (re)gain a solid understanding of geodynamic modelling as a whole.</p>

Martijn Witjes, Leandro Parente, Chris J. van Diemen et al.

A spatiotemporal machine learning framework for automated prediction and analysis of long-term Land Use/Land Cover dynamics is presented. The framework includes: (1) harmonization and preprocessing of spatial and spatiotemporal input datasets (GLAD Landsat, NPP/VIIRS) including five million harmonized LUCAS and CORINE Land Cover-derived training samples, (2) model building based on spatial k-fold cross-validation and hyper-parameter optimization, (3) prediction of the most probable class, class probabilities and model variance of predicted probabilities per pixel, (4) LULC change analysis on time-series of produced maps. The spatiotemporal ensemble model consists of a random forest, gradient boosted tree classifier, and an artificial neural network, with a logistic regressor as meta-learner. The results show that the most important variables for mapping LULC in Europe are: seasonal aggregates of Landsat green and near-infrared bands, multiple Landsat-derived spectral indices, long-term surface water probability, and elevation. Spatial cross-validation of the model indicates consistent performance across multiple years with overall accuracy (a weighted F1-score) of 0.49, 0.63, and 0.83 when predicting 43 (level-3), 14 (level-2), and five classes (level-1). Additional experiments show that spatiotemporal models generalize better to unknown years, outperforming single-year models on known-year classification by 2.7% and unknown-year classification by 3.5%. Results of the accuracy assessment using 48,365 independent test samples shows 87% match with the validation points. Results of time-series analysis (time-series of LULC probabilities and NDVI images) suggest forest loss in large parts of Sweden, the Alps, and Scotland. Positive and negative trends in NDVI in general match the land degradation and land restoration classes, with “urbanization” showing the most negative NDVI trend. An advantage of using spatiotemporal ML is that the fitted model can be used to predict LULC in years that were not included in its training dataset, allowing generalization to past and future periods, e.g. to predict LULC for years prior to 2000 and beyond 2020. The generated LULC time-series data stack (ODSE-LULC), including the training points, is publicly available via the ODSE Viewer. Functions used to prepare data and run modeling are available via the eumap library for Python.

Pacôme Delva, Zuheir Altamimi, Alejandro Blazquez et al.

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.

Ivan Alonso, Cristiano Alpigiani, Brett Altschul et al.

We summarize the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with ESA and national space and research funding agencies.

M. Husak, R. Brajša, D. ŠPoljarić

Ruđer Bošković developed methods for determination of solar rotation elements: the solar equator inclination i, the longitude of the node Ω and the period of solar rotation. In his last work Opera pertinentia ad opticam et astronomiam, published in 1785, in the chapter Opuscule II he described his methods, the formulae with figure descriptions and an example for calculation of the solar rotation elements with detailed numerical explanation using his own observations performed in September 1777. The original numerical procedure was performed using logarithmic formulae. In present work we give a description of the original results of R. Bošković and compare them with our recalculated values.

Phrudth Jaroenjittichai, Koichiro Sugiyama, Busaba H. Kramer et al.

This White Paper summarises potential key science topics to be achieved with Thai National Radio Telescope (TNRT). The commissioning phase has started in mid 2022. The key science topics consist of "Pulsars and Fast Radio Bursts (FRBs)", "Star Forming Regions (SFRs)", "Galaxy and Active Galactic Nuclei (AGNs)", "Evolved Stars", "Radio Emission of Chemically Peculiar (CP) Stars", and "Geodesy", covering a wide range of observing frequencies in L/C/X/Ku/K/Q/W-bands (1-115 GHz). As a single-dish instrument, TNRT is a perfect tool to explore time domain astronomy with its agile observing systems and flexible operation. Due to its ideal geographical location, TNRT will significantly enhance Very Long Baseline Interferometry (VLBI) arrays, such as East Asian VLBI Network (EAVN), Australia Long Baseline Array (LBA), European VLBI Network (EVN), in particular via providing a unique coverage of the sky resulting in a better complete "uv" coverage, improving synthesized-beam and imaging quality with reducing side-lobes. This document highlights key science topics achievable with TNRT in single-dish mode and in collaboration with VLBI arrays.