Hasil untuk "Geodesy"

R. M. Magdaong, Ma. R. C. O. Ang, Ma. R. C. O. Ang et al.

Air pollution poses significant environmental and public health risks, particularly in urban areas of low and middle-income countries like the Philippines. Regulatory air quality monitoring stations, while accurate, are expensive and limited in spatial coverage, highlighting the need for low-cost IoT-based sensor networks to provide broader and real-time air quality data. This study establishes a methodology using Geographic Information Systems (GIS) and a heuristic algorithm to determine locations for deploying low-cost IoT-based air quality sensors in urban environments, focusing on near-road areas in Quezon City. Using multi-criteria analysis, Street Aspect Ratio (SAR), traffic emissions, Global Horizontal Irradiance (GHI), and road proximity were combined to produce a suitability map; scores ranged from 0 to 6. The algorithm then selected sensor locations by combining suitability and population rasters while enforcing a minimum spacing between nodes. In a 40‑sensor test, the resulting networks covered approximately 1.27 - 1.35 million residents (23.0%–24.4% of the city’s population) across weighting schemes while maintaining balanced spatial dispersion. These results indicate that the method achieves substantial population coverage in high‑exposure corridors and aligns with public‑health priorities. The framework is reproducible for other cities to enhance near‑road air quality monitoring and management.

Ç. Çakan, Ç. Çakan, M. T. Yımaz et al.

<p>Accurate precipitation observations are crucial for understanding meteorological and hydrological processes. Most precipitation products rely on station-based observations, either directly or for bias-corrected satellite retrievals. To validate these station-based precipitation products, additional independent data sources are necessary. This study aims to assess the performance of the Global Precipitation Climatology Centre (GPCC) Full Data Monthly Product v2022 and Global Precipitation Climatology Project (GPCP) v3.2 Monthly Analysis Product by estimating the hydrological drought recovery time (DRT) from precipitation and the terrestrial water storage anomaly (TWSA) acquired from satellite gravimetry. This study also evaluates the drought monitoring performance of G3P and JPL mascon total water storage (TWS) monthly solutions from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions. The current study employed two methods to estimate DRT and evaluated the consistency of DRT estimates by calculating the time difference in DRT values derived from the two methods. Globally and across all climate zones, GPCC and GPCP showed comparable performance in hydrological applications with no significant differences in the mean DRT estimates. For the TWS products, DRT estimates using JPL mascon were, on average, 2.6 months longer than those using G3P. However, G3P showed approximately 5.0 % higher consistency than JPL mascon globally and across each climate zone, suggesting its better suitability for more precise drought-related analyses. These findings indicate that G3P outperforms JPL mascon in aligning with precipitation products and offers better consistency in DRT estimation. These results provide valuable insights into the accuracy of precipitation and TWSA products by utilizing hydrological drought characteristics, enhancing our understanding of meteorological and hydrological processes.</p>

Brankica Malić, Vladimir Moser, Damir Rajle et al.

Accurate geodetic surveys are essential for road design, with altimetric accuracy being particularly critical. UAV photogrammetry offers faster and safer data acquisition than conventional methods, but its applicability depends on whether it can meet engineering accuracy standards. This study investigates the altimetric accuracy of UAV photogrammetry through a comparative assessment of surveys conducted on the same urban roundabout in Osijek, Croatia, in 2016 and 2024. By conducting the surveys eight years apart at the same location, the study allows for an assessment of how technological and methodological developments affect survey outcomes. The research evaluates different UAVs and multiple SfM software packages in a comparative framework, highlighting how UAV–software combinations affect results, rather than attributing accuracy solely to hardware or processing. The results of the conducted research indicate a significant increase in the accuracy of the UAV photogrammetric survey method. Through a proper combination of UAVs and SfM processing software, it is possible to achieve an accuracy within 2 cm and an RMSE of 1.2 cm, which is in line with the accuracy of a standard survey method like GNSS CROPOS. The results underline that UAV photogrammetry, when properly planned and executed, can now deliver altimetric accuracy sufficient for most road construction tasks, providing a reliable and cost-effective alternative to conventional geodetic surveys.

Meng Zhang, Meng Zhang, Chao Qi et al.

The utilization of synthetic aperture radar (SAR) for depth inversion is crucial for accurate underwater mapping. However, current SAR-based techniques face challenges in segmentation accuracy, which directly affects inversion precision and spatial resolution. Traditional segmentation methods lack efficiency and often result in low-resolution outcomes. To address these issues, we propose a novel SAR water depth inversion method based on variable window sliding segmentation. This method optimizes nearshore image utilization by dynamically adjusting the pixel size and preventing coastline encroachment, leading to more precise swell wavelength measurements. When applied to the eastern sea off Naraha, Japan, our method achieved a minimum mean relative error (MRE) of 9.2% for shallow waters (0 to 20 m depth) and 4.9% for deeper waters (80 to 100 m depth). These results significantly improve upon those of traditional methods, which typically show MREs ranging from 10% to 30%. Additionally, our method achieves a maximum spatial resolution of 5.5 m, a notable advancement in nearshore depth measurement. The study also revealed that different depth ranges and function types, particularly linear and atanh functions, impact measurement performance, demonstrating superior accuracy across multiple metrics.

Xuanjian Wang, Jian Cao, Hualin Shu et al.

Optical clocks have extremely attractive applications in many fields, including time-frequency metrology, validation of fundamental physical principles, and relativistic geodesy. The 467 nm octupole transition in 171Yb+ ion exhibits intrinsic insensitivity to magnetic field and an ultra-long clock state lifetime of 1.6 years. In addition, the entire laser system can be realized by semiconductor technologies, rendering this platform uniquely advantageous for developing high-precision, compact and transportable optical clocks. Here, we report the development of a compact optical clock based on the 467 nm transition of a single 171Yb+ ion. Using a narrow linewidth 467 nm laser to interrogate the clock transition, we obtain a near-Fourier-limited linewidth of 2.3 Hz in an integrated ion trapping system. Self-comparison demonstrated a frequency instability of 2.2E-15/sqrt(tau/s) with an interrogation time of 180 ms, which reaches the high parts in E-18 level with an averaging time of only one day. These work laid the technical foundation for the subsequent clock systematic evaluation and the packaging of each subsystem into an engineering prototype with high-precision at the level of E-18.

Łukasz Jan Orman, Luiza Dębska, Lidia Dąbek et al.

The present paper experimentally analyses the subjective assessment of indoor environment comfort based on a questionnaire survey conducted in a climate chamber located at Kielce University of Technology (Poland), if two types of face masks are worn by the respondents: thin (medical) and thick (cotton-made) masks. Air temperature and relative humidity in the chamber ranged from around 19 to 28oC and 20 – 70%, respectively. Precise measurement of the microclimate parameters was obtained with a microclimate meter, which recorded air temperature and relative humidity at the moment of completing the questionnaires. The respondents were of similar age (22 – 31 years old) and wore two types of clothing during the experiments: summer and winter, which differed by thermal resistance. This value amounted to 0.5 clo for the summer outfit and 0.8 clo for the winter one.In total 960 questionnaires were analysed in the study. The results indicate that the increase in air temperature led to poorer overall comfort, while the largest comfort sensation was recorded for the most favourable thermal sensation range. In general, thicker masks provided lower overall comfort than thinner masks for all relative humidity values.

Chunli Kuang, Xianxin Tu, Hui Wang

The new SS-Y extensometer has been in operation for 10 years at Yichang seismic station. Data obtained by the extensometer over the period of 2014 to 2022 at Yichang seismic station were analyzed using the Venedikov harmonic analysis method. The results showed that the internal quality of the data was good. The values of the tide factor of M2 wave of the two components were much greater than 1. The observation accuracy of the NS component is higher than that of the EW component. According to the geophysical network observation data tracking and analysis platform, it was found that there were various types of interference of SS-Y extensometer over the period of 2014 to 2022. After comprehensive analysis, it can be summarized into the influence of four categories of interference factors (observation system, natural environment, site environment and human interference), and the curve was mostly characterized by sudden jumps, steps, breaks, error data, synchronous trend changes and so on. Such as, after filtering processing of the site environmental interference occurred on February 21, 2021, the two components can be clearly recorded to the sharp pulse explosion interference. The classification and screening of these interference characteristics can provide a reference for the accurate identification and abnormal determination of the station data in the future.

Idania C. Briceño de Urbaneja, Josep E. Pardo-Pascual, Carlos Cabezas-Rabadán et al.

Sandy coastlines are very dynamic spaces affected by a variety of natural and human factors. In Central Chile, changes in oceanographic and wave conditions, modes of inter-annual climate variability such as El Niño Southern Oscillation (ENSO), and extreme events such as earthquakes and tsunamis condition the beach morphology. At the same time, direct human actions alter the arrival of sediments to the coast and their alongshore distribution. Despite the relevance of the beaches for this coastal region and the interesting relationship their morphology has with the aforementioned factors, there is a lack of robust morphological datasets to provide a deep characterization and understanding of the dynamism of the Chilean coast. Based on the information provided by satellite-derived shorelines (SDSs) defined by using the SHOREX algorithm, this paper characterizes the morphological changes of Playa Grande in Cartagena Bay (Central Chile) during the period 1985–2019. The shoreline position data are analyzed in the context of changing beach transforming elements, allowing for a better understanding of the changes according to multiple drivers. While some of these factors, such as earthquakes or coastal storms, have a punctual character, changes in wave patterns vary at different time scales, from seasonal to multi-annual, linked to climate phases such as ENSO. Its effects are translated into shoreline erosion and accretion conditioned by the morphology and orientation of the coast while influenced by the availability of sediment in the coastal system. According to that, a conceptual model of the dynamism and redistribution of sediment in the Bay of Cartagena is proposed. The work proves the high utility that the systematic analysis of multi-decadal SDS datasets obtained from the images acquired in the optical by the Landsat and Sentinel-2 offer for beach monitoring and understanding the coastal dynamism.

Angel T. Apostolov, Iliana N. Apostolova, Julia M. Wesselinowa

Using the microscopic s-f model and Green’s function theory, we study the temperature dependence of the band gap energy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula> and the phonon energy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> and damping <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>γ</mi></semantics></math></inline-formula> of ferro- and antiferromagnetic semiconductors, i.e., with different signs of the s-f interaction constant <i>I</i>. The band gap is a fundamental quantity which affects various optical, electronic and energy applications of the materials. In the temperature dependence of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula> and the phonon spectrum, there is a kink at the phase transition temperature <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>T</mi><mi>C</mi></msub></semantics></math></inline-formula> or <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>T</mi><mi>N</mi></msub></semantics></math></inline-formula> due to the anharmonic spin–phonon interaction (SPI) <i>R</i>. Moreover, the effect of the SPI <i>R</i> and electron–phonon interaction (EPI) <i>A</i> on these properties is discussed. For <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>I</mi><mo>></mo><mn>0</mn><mo>,</mo><mi>R</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula> decreases with increasing SPI and EPI, whereas for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>I</mi><mo><</mo><mn>0</mn><mo>,</mo><mi>R</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>, there is a competition; <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula> increases with raising the EPI and decreases for enhanced SPI. For <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mo><</mo><mn>0</mn></mrow></semantics></math></inline-formula>, in both cases, the SPI and EPI reduce <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula>. The magnetic field dependence of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>E</mi><mi>g</mi></msub></semantics></math></inline-formula> for the two signs of <i>I</i> and <i>R</i> is discussed. The SPI and EPI lead to reducing the energy of the phonon mode <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> = 445 cm⁻¹ in EuO (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>I</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mo><</mo><mn>0</mn></mrow></semantics></math></inline-formula>), whereas <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> = 151 cm⁻¹ in EuSe (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>I</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>) is enhanced with increasing EPI and reduced with SPI. Both the SPI and EPI lead to an increasing of the phonon damping in EuO and EuSe. The results are compared with the existing experimental data.

Fangchao Yang, Yan Zhu, Xiaofei Jin et al.

Precision space inertial sensors are imperative to Earth geodesy missions, gravitational wave observations and several fundamental physics experiments in space. In these missions, the residual acceleration noise of the test mass(TM) caused by the forces from inertial sensor components and environment is supposed to be kept below a certain level. As a number of forces contributing to residual acceleration are related to actuation system, developing a precise actuation system to exclude any erroneous force and obtain an ultra sensitive value for TM acceleration noise is necessary and essential. However, it is difficult to test the actuation system on ground. In this paper, a torsion pendulum is established to test the influence of actuation system on TM torque noise and a closed-loop control system combined torsion pendulum and parts of actuation modules is designed to assess the performance of actuation control algorithm. The experimental results show that the parameters in an actuation system will introduce additional torque noise and the maximum noise can reach as much as 10^{-13}Nm /Hz^{1/2} at 1 mHz. The stable tracking error for the closed-loop system is about 10^{-7}, indicating that the combination system achieves good tracking performance and robustness for TM rotation control in different conditions of inertial sensors.

M. O. Hecht, Kumar Saurav, Evangelos Vlachos et al.

Quantum sensors promise revolutionary advances in medical imaging, energy production, mass detection, geodesy, foundational physics research, and a host of other fields. In many sensors, the signal takes the form of a changing qubit frequency, which is detected with an interference measurement. Unfortunately, environmental noise decoheres the qubit state, reducing signal-to-noise ratio (SNR). Here we introduce a protocol for enhancing the sensitivity of a measurement of a qubit's frequency in the presence of decoherence. We use a continuous drive to stabilize one component of the qubit's Bloch vector, enhancing the effect of a small static frequency shift. We demonstrate our protocol on a superconducting qubit, enhancing SNR per measurement shot by 1.65$\times$ and SNR per qubit evolution time by 1.09$\times$ compared to standard Ramsey interferometry. We explore the protocol theoretically and numerically, finding maximum enhancements of 1.96$\times$ and 1.18$\times$, respectively. We also show that the protocol is robust to parameter miscalibrations. Our protocol provides an unconditional enhancement in signal-to-noise ratio compared to standard Ramsey interferometry. It requires no feedback and no extra control or measurement resources, and can be immediately applied in a wide variety of quantum computing and quantum sensor technologies to enhance their sensitivities.

Victor Montenegro

Precision measurements of gravitational acceleration, or gravimetry, enable the testing of physical theories and find numerous applications in geodesy and space exploration. By harnessing quantum effects, high-precision sensors can achieve sensitivity and accuracy far beyond their classical counterparts when using the same number of sensing resources. Therefore, developing gravimeters with quantum-enhanced sensitivity is essential for advancing theoretical and applied physics. While novel quantum gravimeters have already been proposed for this purpose, the ultimate sensing precision, known as the Heisenberg limit, remains largely elusive. Here, we demonstrate that the gravimetry precision of a conditional displacement spin-mechanical system increases quadratically with the number of spins: a Heisenberg-limited spin-mechanical gravimeter. In general, the gravitational parameter is dynamically encoded into the entire entangled spin-mechanical probe. However, at some specific times, the mechanical degree of freedom disentangles from the spin subsystem, transferring all the information about the gravitational acceleration to the spin subsystem. Hence, we prove that a feasible spin magnetization measurement can reveal the ultimate gravimetry precision at such disentangling times. We predict an absolute gravimetry uncertainty of $10^{-11}\text{m/s}^2$ to $10^{-6}\text{m/s}^2$, without relying on free-fall methodologies, ground-state cooling of the mechanical object, and robust against spin-mechanical coupling anisotropies.

Giuseppe Di Somma, Nicolò Beverini, Giorgio Carelli et al.

The study of local deformations is a hot topic in geodesy. Local rotations of the crust around the vertical axis can be caused by deformations. In the Gran Sasso area the ring laser gyroscope GINGERINO and the GNSS array are operative. One year of data of GINGERINO is compared with the ones from the GNSS stations, homogeneously selected around the position of GINGERINO, aiming at looking for rotational signals with period of days common to both systems. At that purpose the rotational component of the area circumscribed by the GNSS stations has been evaluated and compared with the GINGERINO data. The coherences between the signals show structures that even exceed 60$\%$ coherence over the 6-60 days period; this unprecedented analysis is validated by two different methods that evaluate the local rotation using the GNSS stations. The analysis reveals that the shared rotational signal's amplitude in both instruments is approximately $10^{-13} rad/s$, an order of magnitude lower than the amplitudes of the signals examined using the coherence method. The comparison of the ring laser data with GNSS antennas provides evidence of the validity of the ring laser data for very low frequency investigation, essential for fundamental physics test.

Wyszomirski Michał

The article discusses the possibility of using Redis key-value NoSQL database to process building data in different BIM-GIS integration solutions. Whichever data integration model is adopted, it will require an efficient serving of building data in Industry Foundation Classes (IFC) format. The author proposed a method of processing building data in the Redis database to support the process of feeding IFC data to his own concept of an integrated BIM-GIS database. However, other approaches to BIM-GIS integration, including the import of IFC data to CityGML, or the construction of an integrated BIM-GIS solution based on data integration at the application server level or client application in client-server environments, also require an efficient IFC data serving mechanism. This article describes three methods of storing IFC data in a Redis database using different data types and formats. The author conducted performance tests of the proposed methods in the processing of fourteen test BIM models. The article contains detailed results of the model processing tests in the Redis database.

Yohei Yukutake, Ryou Honda, Motoo Ukawa et al.

Abstract The feeding system of magmatic fluid from the volcanic root to a shallow magma reservoir remains a poorly understood issue. Seismic events, including volcanic tremors and low-frequency earthquakes, in a deep part beneath volcanos are key observations for understanding the feeding system at the depth. Although deep low-frequency (DLF) earthquakes beneath volcanos have been recognized universally through dense seismic observations, volcanic tremors with harmonic frequency components originating at volcanic roots have rarely been observed. Here, we report the observation of a harmonic volcanic tremor event that occurred beneath the Hakone volcano on May 26, 2019. The tremor signal continued for approximately 10 min and was recognized at seismic stations 90 km away from the Hakone volcano. The apparent velocity of the tremor wave train is 5 km/s, corresponding to the S-wave velocity of the lower crust beneath the Hakone volcano. The frequency components varied with time. In the initial part of the tremor signal, a spectrum had a broad peak of around 1.2 Hz, whereas the tremor became harmonic with a sharp fundamental peak at 0.98 Hz in the latter part, increasing its amplitude. We estimated the source location of the volcanic tremor using the relative arrival times of the waveform envelope. The optimal source locations were estimated at a deep extension of the hypocenter distribution of the DLF earthquakes beneath the Hakone volcano, around the depth level of Moho discontinuity. The DLF earthquakes were activated immediately before the onset time of the volcanic tremor and continued for several months. The harmonic volcanic tremor may have been generated by the migration of magmatic fluid in the volcano’s deep region. Graphical Abstract

Kuangchao Wu, Wen-Bin Shen, Xiao Sun et al.

According to general relativity theory (GRT), by comparing the frequencies between two precise clocks at two different stations, the gravity potential (geopotential) difference between the two stations can be determined due to the gravity frequency shift effect. Here, we provide experimental results of geopotential difference determination based on frequency comparisons between two remote hydrogen atomic clocks, with the help of common-view satellite time transfer (CVSTT) technique. For the first time we apply the ensemble empirical mode decomposition (EEMD) technique to the CVSTT observations for effectively determining the geopotential-related signals. Based on the net frequency shift between the two clocks in two different periods, the geopotential difference between stations of the Beijing 203 Institute Laboratory (BIL) and Luojiashan Time--Frequency Station (LTS) is determined. Comparisons show that the orthometric height (OH) of LTS determined by the clock comparison is deviated from that determined by the Earth gravity model EGM2008 by (38.5$\pm$45.7)~m. The results are consistent with the frequency stabilities of the hydrogen clocks (at the level of $10^{-15}$~day$^{-1}$) used in the experiment. Using more precise atomic or optical clocks, the CVSTT method for geopotential determination could be applied effectively and extensively in geodesy in the future.

Christopher Dieck, Megan C. Johnson, Daniel S. MacMillan

Frequent, low-latency measurements of the Earth's rotation phase, UT1$-$UTC, critically support the current estimate and short-term prediction of this highly variable Earth Orientation Parameter (EOP). Very Long Baseline Interferometry (VLBI) Intensive sessions provide the required data. However, the Intensive UT1$-$UTC measurement accuracy depends on the accuracy of numerous models, including the VLBI station position. Intensives observed with the Maunakea (Mk) and Pie Town (Pt) stations of the Very Long Baseline Array (VLBA) illustrate how a geologic event (i.e., the $M_w$ 6.9 Hawai`i Earthquake of May 4th, 2018) can cause a station displacement and an associated offset in the values of UT1$-$UTC measured by that baseline, rendering the data from the series useless until it is corrected. Using the non-parametric Nadaraya-Watson estimator to smooth the measured UT1$-$UTC values before and after the earthquake, we calculate the offset in the measurement to be 75.7 $\pm$ 4.6 $μ$s. Analysis of the sensitivity of the Mk-Pt baseline's UT1$-$UTC measurement to station position changes shows that the measured offset is consistent with the 67.2 $\pm$ 5.9 $μ$s expected offset based on the 12.4 $\pm$ 0.6 mm total coseismic displacement of the Maunakea VLBA station determined from the displacement of the co-located global navigation satellite system (GNSS) station. GNSS station position information is known with a latency on the order of tens of hours, and thus can be used to correct the a priori position model of a co-located VLBI station such that it can continue to provide accurate measurements of the critical EOP UT1$-$UTC as part of Intensive sessions. The VLBI station position model would likely not be updated for several months. This contrast highlights the benefit of co-located GNSS and VLBI stations in support of the monitoring of UT1$-$UTC with single baseline Intensives. Abridged.

Di Zhang, Jiming Guo, Tianye Fang et al.

Tropospheric mapping function plays a vital role in the high precision Global Navigation Satellites Systems (GNSS) data processing for positioning. However, most mapping functions are derived under the assumption that atmospheric refractivity is spherically symmetric. In this paper, the pressure, temperature, and humidity fields of ERA5 data with the highest spatio-temporal resolution available from the European Centre for Medium-range Weather Forecast (ECMWF) were utilized to compute ray-traced delays by the software WHURT. Results reveal the universal asymmetry of the hydrostatic and wet tropospheric delays. To accurately represent these highly variable delays, a new mapping function that depends on elevation and azimuth angles—Tilting Mapping Function (TMF)—was applied. The basic idea is to assume an angle between the tropospheric zenith direction and the geometric zenith direction. Ray-traced delays served as the reference values. TMF coefficients were fitted by Levenberg–Marquardt nonlinear least-squares method. Comparisons demonstrate that the TMF can improve the MF-derived slant delay’s accuracy by 73%, 54% and 29% at the 5° elevation angle, against mapping functions based on the VMF3 concept, without, with a total and separate estimation of gradients, respectively. If all coefficients of a symmetric mapping function are determined together with gradients by a least-square fit at sufficient elevation angles, the accuracy is only 6% lower than TMF. By adopting the b and c coefficients of VMF3, TMF can keep its high accuracy with less computational cost, which could be meaningful for large-scale computing.

Qiming Zhou, Ali Ismaeel

Timely and reliable estimation of regional crop yield is a vital component of food security assessment, especially in developing regions. The traditional crop forecasting methods need ample time and labor to collect and process field data to release official yield reports. Satellite remote sensing data is considered a cost-effective and accurate way of predicting crop yield at pixel-level. In this study, maximum Enhanced Vegetation Index (EVI) during the crop-growing season was integrated with Machine Learning Regression (MLR) models to estimate wheat and rice yields in Pakistan’s Punjab province. Five MLR models were compared using a fivefold cross-validation method for their predictive accuracy. The study results revealed that the regression model based on the Gaussian process outperformed over other models. The best performing model attained coefficient of determination (R2), Root Mean Square Error (RMSE, t/ha), and Mean Absolute Error (MAE, t/ha) of 0.75, 0.281, and 0.236 for wheat; 0.68, 0.112, and 0.091 for rice, respectively. The proposed method made it feasible to predict wheat and rice 6–8 weeks before the harvest. The early prediction of crop yield and its spatial distribution in the region can help formulate efficient agricultural policies for sustainable social, environmental, and economic progress.