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The performance of Beidou satellite-based augmentation system (BDSBAS) single frequency augmentation service was evaluated and analyzed according to the shortcomings of the research on the corresponding operational performance support of the BDSBAS with the actual data. The calculation process of BDSBAS accuracy enhancement and integrity enhancement was comprehensively sorted out based on the relevant international standards. The process of accuracy enhancement and integrity enhancement was achieved through the publicly broadcast BDSBAS-BIC messages, and the enhancement results were used to evaluate the service performance of BDSBAS in China in the second quarter of 2022 in terms of precision, integrity and availability. The results show that during the test period, the BDSBAS single frequency augmentation service can support the accuracy and availability required for approach procedure with vertical guidance (APV)-I operation, and the horizontal and vertical accuracies respectively range from 1.5 to 5.5 m and from 2.5 to 10.3 m with the availability of APV-I operation of 99.871% (better than 99.000%). Although the transient integrity does not support APV-I, the positioning error is completely enveloped by the protection level without misleading information and dangerous misleading information events. [ABSTRACT FROM AUTHOR]

Both human physiological activity and random noise have an impact on the accuracy of cerebral blood oxygen measurement data. It is necessary to solve some noise interference encountered during signal acquisition to improve the measurement accuracy of cerebral blood oxygen detection. This study proposes a denoising method of cerebral oximetry signals by combining ICEEMDAN (Improved Complete Empirical Mode Decomposition with Adaptive Noise) and SampEn (Sample Entropy). Specifically, the modal decomposition of the cerebral blood oxygen signal is performed using ICEEMDAN to obtain the IMF components with different time complexity. The time complexity of each IMF (Intrinsic Mode Function) component is judged by the sample entropy value, and the appropriate component is selected to reconstruct the signal according to the sample entropy value of each IMF component, thus realizing the noise removal of the original signal. Experimental results show that the proposed method can effectively remove the original cerebral blood oxygen signal and realize the accuracy improvement of the collected data, thus improving the accuracy of cerebral blood oxygen detection. [ABSTRACT FROM AUTHOR]

The No.1 and No.2 liquid bulk cargo berths in Jida Port Area of Maoming Port are independent pier type cylinder caisson gravity docks. This paper focuses on the precision control of the prefabricated cover plate on the upper part of the circular caisson and the splitting installation of the berthing components. In the absence of effective cover in the open sea, BIM technology was used to simulate component collision detection, precise alignment of the steel bars of the separate components, and temporary installation stability analysis, in order to optimize the structural type of the separate components and select the optimal lifting plan, refine the positioning and reinforcement construction process, improve the accuracy and efficiency of prefabricated cover plates and berthing components installation through visualization, informatization, and standardization, reduce project costs and maritime lifting safety risks, and provide experience and reference for the installation of large prefabricated components similar to LPG terminals in the future. [ABSTRACT FROM AUTHOR]

Accuracy is an important indicator of the three-dimensional (3D) model of UAV oblique photography.Conventional modeling need to deploy Ground Control Points (GCPs), which is inefficient and costly.Control-free modeling does not require GCPs, which is efficient but not accurate.Here, we propose a 3D modeling approach for oblique photography with post-processed image control.The study was carried out in the east area of Nanjing University of Information Science & Technology.The results show that both the 3D models established by conventional modeling and post-processed image control modeling are accurate, with plane errors and elevation errors less than 0.05 m, meeting the modeling requirements of high efficiency, high precision and low cost.However, the post-processed image control modeling avoids the making and maintaining of the image control points, instead, it deploys the existing high-precision 3D model to select image control points and extract the coordinates.The proposed approach can be applied to regular updating of high-precision 3D real scene models for cities, towns, roads, etc. [ABSTRACT FROM AUTHOR]

In order to improve feeding stability of industrial pulverized coal boiler, a kind of disc feeder was developed. The disc feeder is mainly composed of three parts, i.e. pulverized coal fluidization system, feeding disc system and pressure balance system. Pulverized coal around the feeding disc was in a stabilized fluidiza-tion state and low pulsation feeding can be realized. Performance test system was developed and performances of the disc feeder under 6 typical working conditions were tested. At last, the disc feeder was used in industrial pulverized coal boiler system and application effect of the disc feeder was verified. According to the experimental data obtained from the performance test system, the maximum feeding amount of the disc feeder was 2.8 t/h. Fluctution of feeding amount was less than ±2%. According to the actual application result, practical feeding amount of the disc feeder was 2.56 t/h. Also, average change of furnace negative pressure and oxygen content were decreased over 50%. The results show that, the disc feeder meets the design requirements and stability of the disc feeder was verified. [ABSTRACT FROM AUTHOR]

A simplified bilateral trigonometric leveling was used to survey the differences of elevations of the top of the piers for the non-navigable span of Hongkong-Zhuhai-Macao Bridge under Contract CB03, which could quickly obtain precise and accurate measurements. Equal-height centering rods and prisms of the same specifications and models, instead of surveying rods, were placed on the benchmarks at the top of different piers and two total stations were employed to survey respectively the elevation differences of the same shore and the elevation differences between the calculated benchmarks of the opposite shore vertical angle and the opposite shore horizontal distances to increase the checking conditions for the loop closure errors in the segments of survey, but the total station was not positioned alternately on the survey station and the benchmarks. The paper introduces the simplified bilateral trigonometric leveling method, the conditions in the surveyed area, and the scheme for bilateral trigonometric leveling. The number of surveying indicators and statistic data distributed in the intervals between the observed values of elevation difference in the 96 surveying segments and 24 loop closures was established according to the observed values of elevation difference and loop closures formed during the construction of Hongkong-Zhuhai-Macao Bridge and precision calculations and analyses were made with the results showing that the presented method can meet the requirement of second order leveling accuracy. [ABSTRACT FROM AUTHOR]

Aero-engine casings are important connecting and bearing components in aero-engine. Because of their complex structures, weak rigidity and difficult-to-machining materials, there are many manufacturing problems remaining for casing part such as serious machining deformation and poor accuracy of wall thickness, which has become a bottleneck restricting the development and production of new aero-engines. Aiming at this requirement, we propose a new method named counter-rotating electrochemical machining (CRECM). During CRECM, a revolving cathode tool is used, and the anode workpiece and cathode tool rotate oppositely at the same rotational speed. As the material is dissolved accurately layer by layer in CRECM, the large thin-walled casing part can be machined precisely without deformation. The fundamental scientific problems involved in CRECM such as the anode shaping rule, the pulse dynamic dissolution mechanism of difficult-to-cut materials and the distribution characteristics of electrolyte flow field are revealed. The key technologies such as cathode tool design, pitting inhibition of titanium alloy and optimization design of electrolyte flow field are broken through. Moreover, a large-scale CRECM machine with independent intellectual property rights has been developed, and large thin-wall casing parts are fabricated efficiently and precisely. The research provides important technical support for the development and production of new aero-engines. [ABSTRACT FROM AUTHOR]

Multi cooperative satellites can provide multi spectral, multi temporal, multi factor, multi scale and multi-level remote sensing data, which is rich in valuable information for numerical weather prediction (NWP). In order to support earth system seamless fine gridded forecasting service in the future, the application status of satellite observation big data was discussed for numerical weather prediction from the aspects of detection variables, time density, spatial coverage, horizontal and vertical resolution, as well as accuracy and timeliness. At the same time, in order to make satellite big data be highly tolerant with NWP, the challenges and prospects were summarized, such as multi-satellite integrated and consistent processing, all-weather, coupled data assimilation methods, deep integration with artificial intelligence, and interaction between satellite observation and prediction. [ABSTRACT FROM AUTHOR]

In the process of cultivated land quality data investigation and collection, there will be missing data due to human, environmental, and other factors. However, the current missing data-filling methods have insufficient applicability. In order to improve the cultivated land quality database and evaluation accuracy, it is important to explore missing data-filling methods in cultivated land quality evaluation. In this study, the cultivated land quality database of Conghua District Guangzhou City was used as the sample set. According to the spatial correlation and spatial distribution, the dataset was divided into spatial and non-spatial correlation datasets. Various filling methods were used to simulate the missing data filling, and a cross method was used to verify the accuracy. The results indicated the proportion of total outliers was less than 1.2%, and 25 factors such as elevation, temperature, and available zinc showed spatial correlation. The four-image nearest neighbor algorithm presented the highest filling accuracy for spatial association data, and the accuracy was as high as 80% when the missing rate was less than 20%. The accuracy decreased with the increase in the missing rate. The four-image nearest neighbor algorithm was followed by K-nearest neighbor algorithm（KNN）, expectation maximization algorithm, multiple interpolation algorithm, and regression model algorithm. The four-image nearest neighbor algorithm showed better accuracy than K-nearest neighbor algorithm when the data was dense. For the non-spatial correlation dataset, the highest filling accuracy was the similar aggregation filling algorithm, which could maintain more than 80% accuracy within 25% of the missing rate, followed by expectation maximization algorithm, multiple interpolation algorithm, and regression model algorithm. To sum up, the four-image nearest neighbor algorithm and the similar aggregation filling algorithm proposed in this study show higher accuracy, more stable effect, and wider practicability than other algorithms for filling missing data in cultivated land quality evaluation [ABSTRACT FROM AUTHOR]

In the new retail scene, there are a large variety of products on self-service shelves, which are susceptible to external factors such as light. In addition, customers' hands or bodies will block the key information of products when they hold the products. Therefore, only using the image recognition algorithm in the natural scene cannot meet the application requirements of the self-service shelves. Aiming at the characteristics of the actual application scene of self-service shelves, a handheld products recognition solution is proposed based on the human joint point positioning algorithm and the image classification algorithm in deep learning. Firstly, the human joint point positioning algorithm is used to accurately locate the joint points of the upper body of the customers. Secondly, the image classification algorithm mainly identifies the images containing the main features of the products, which are centered on the joint points of the arm. In order to improve the practicality of the algorithm, L-CPM and EP-L-CPM are designed to improve the Convolutional Pose Machine (CPM) from the two aspects of the speed and accuracy of joint point positioning. The public dataset and the human posture dataset of actual self-service shelves scene are used to verify the performance of algorithms. Experimental results show that the proposed algorithm can accurately and efficiently locate the human body joints. [ABSTRACT FROM AUTHOR]

Suitable water volume equipment can reduce the cost of irrigation area operation and management, improve the management level of irrigation area, increase economic and ecological benefits and promote the development of modern irrigation area construction. This study based on the theory of system engineering, scientifically and comprehensively analyzed the influencing factors. The comprehensive evaluation index system were made up with one goal layer, three grades and thirteen indices and established quantitative calculation of evaluation criterion of water. Taking comparison of water measuring equipment of Tanglai canal irrigation area in the Yellow River irrigation region in Ningxia as an example, it conducted instance verification. The outcomes show that among the 6 categories equipment, 2 categories reach medium level and 4 categories are at poorer level. It is recommended that equipment 4 ( score 72.57) and equipment 6 ( score 60.63) can be used for branch canal and lateral canal of the Yellow River irrigation area in Ningxia. [ABSTRACT FROM AUTHOR]

GXNU-AMS, a compact 14C accelerator mass spectrometer, jointly developed by the Chinese Institute of Atomic Energy and Guangxi Normal University, and it was installed and commissioned in Guangxi Normal University. Without the traditional mode of SF6 pressure tank, the terminal of the system was designed as an open insulated high voltage platform, which reduces the construction size of the traditional accelerator to be about 2X2.5 square meters. Helium gas stripping was used to eliminate t he interference of molecular ions, and the maximum operating voltage was 230 kV. At present, the measurement accuracy of the instrument is 0.5%, and the measurement sensitivity is 14C/12C=l.0X10-14 (measurement background is 40000 years), which can meet the measurement requirements in the fields of life sciences and archaeology. In this paper, the experimental conditions and reliability of GXNU-AMS were studied. The pre-accelerator voltage and the main accelerator voltage were set to be 30kV and 200kV, respectively, the pressure of stripping gas was set to be 5.1X10-3 Pa, and the charge state +C was chosen after accelerated. The PMC value of the self-made standard sample was consistent with the values of international OX]] standard sample. The experiment results showed that the system can be operated with high measurement accuracy and good stability, which layed a good foundation for further research on this facility. This work is helpful for the construction of more compact and lower cost desktop AMS equipment for meeting the growing demand for scientific research and sample measurement. [ABSTRACT FROM AUTHOR]

Promoted by the Hydrological Bureau of the Ministry of Water Resources, the two ADCPs which were produced by the Institute of Acoustics, Chinese Academy of Sciences and Zhonghaida Corporation have passed the new product appraisal of the Comprehensive Bureau of the Ministry of Water Resources. In order to accelerate the application of domestic ADCPs in the collection of basic hydrological data, the Hydrological Bureau of the Yangtze River Water Conservancy Committee had carried out the applicability test and precision comparison according to the requirements of the norms. The results show that the accuracy of domestic ADCP is equivalent to that of RDI ADCP with the same frequency, which meets the accuracy requirements of flow measurement specifications. [ABSTRACT FROM AUTHOR]

Remote island construction environment is complicated, there are problems such as poor wireless communication conditions and difficulty in powering the positioning devices. In order to promote the application of Beidou navigation satellite system (BDS) in coastal island construction projects, the static positioning accuracy of BDS in coastal islands was assessed. Considering the power consumption and communication pressure, the BDS positioning accuracy of different distances, different observation periods and different sampling rales were analyzed. Statistics show, short-distance positioning accuracy of BDS B1 and B2 earner is equivalent to GPS; The 1 h positioning precision is comparable to 2 h at the sampling interval 10 s, the difference from the GPS positioning solution is less than 1 cm; With 1 h observation periods, the positioning accuracy of sampling interval 30 s is basically the same as the 10 s solution. Short—distance positioning technology of BDS B1 and B2 carrier can completely replace GPS in coastal island projects. [ABSTRACT FROM AUTHOR]

Remote island construction environment is complicated, there are problems such as poor wireless communication conditions and difficulty in powering the positioning devices. In order to promote the application of Beidou navigation satellite system (BDS) in coastal island construction projects, the static positioning accuracy of BDS in coastal islands was assessed. Considering the power consumption and communication pressure, the BDS positioning accuracy of different distances, different observation periods and different sampling rates were analyzed. Statistics show, short-distance positioning accuracy of BDS B1 and B2 carrier is equivalent to GPS; The 1 h positioning precision is comparable to 2 h at the sampling interval 10 s, the difference from the GPS positioning solution is less than 1 cm; With 1 h observation periods, the positioning accuracy of sampling interval 30 s is basically the same as the 10 s solution. Short-distance positioning technology of BDS B1 and B2 carrier can completely replace GPS in coastal island projects. [ABSTRACT FROM AUTHOR]

There is a demand for attitude in mobile surveying systems. Thus, a direct attitude determination method based on vehicle-mounted three-antenna global navigation satellite system (GNSS) is proposed. Principles behind attitude determination were analyzed and the formulae for the folution were derived. A simple method is proposed to determine the quadrants of the yaw angles, which solves the multi-value problem. The data from a land vehicle are processed, and a reference attitude from a high-accuracy inertial navigation system (INS) was used to evaluate the accuracy and reliability of the attitude determined from three-antenna GNSS. The results indicate that the attitude determined from three-antenna GNSS can achieve high accuracy and reliability. This method is simple in calculation and avoids the singularity problem. [ABSTRACT FROM AUTHOR]

BACKGROUND: With the improvement of medical imaging technology, the visualization of human anatomy has been further developed; the role of three-dimensional (3D) reconstruction in medical treatment is also becoming increasingly prominent. Mimics is the most widely used medical image reconstruction software. Arigin 3D Pro is a recently developed 3D reconstructed medical software system based on 3D printing. OBJECTIVE: To study the accuracy of 3D reconstruction models obtained by using Arigin 3D Pro and Mimics with medical images. METHODS: The image data of liver, spine, knee joint and heart were selected, and the deviations of two software reconstruction models were analyzed based on the 3D model reconstructed by Mimics. Totally 10 cases of skull and 1 case of femoral comminuted fracture image data were selected and reconstructed. Each reconstruction model was measured with 10 groups of feature sizes to evaluate the differences between the two software programs. RESULTS AND CONCLUSION: Arigin 3D Pro and Mimics were used to reconstruct the liver, spine, knee and heart data. The mean ± standard deviation of model deviations were (0.93 ± 1.05), (0.36 ± 0.74), (0.45 ± 0.74), (0.18 ± 0.41) mm. It took 3 minutes and 35 minutes for Arigin 3D Pro and Mimics to reconstruct the liver model respectively, and both software reconstructed other models for less than 1 minute. There was no statistically significant difference between the feature sizes of the two software for the 3D reconstruction models of skull and femoral comminuted fracture data (P > 0.05). The 3D reconstruction model of Arigin 3D Pro is comparable to that of Mimics. For the liver model, the reconstructed time of Arigin 3D Pro is significantly shorter than that of Mimics. [ABSTRACT FROM AUTHOR]

Motivated by the idea of total least squared method, a total error-based multiquadric method (MQ-T) has been developed to decrease the effect of both horizontal and vertical errors inherent in sample points on surface modeling. Two examples including a numerical test and a real-world example were, respectively, employed to test the robustness of MQ-T to sample errors. The numerical test indicates that when sample points are only subject to vertical errors, MQ-T has a similar performance to MQ. When sample points are subject to horizontal errors, MQ-T is more accurate than MQ. In the real-world example, MQ-T was used to construct DEMs with sample points collected by a total station instrument, and its accuracy was compared with those of classical interpolation methods including inverse distance weighting, ordinary Kriging (Kriging) and ANUDEM. Results indicate that with the decrease of sample density, the interpolation accuracies of all methods become lower. Regardless of sample density, MQ-T is always more accurate than the other methods. Yet, compared with Kriging, MQ-T has a peak-cutting problem. [ABSTRACT FROM AUTHOR]

【Objective】The present paper was conducted to study the accuracy of using Landsat8 OLI remote sensing image to monitor the rice planting area in hilly areas of Sichuan province.【Method】Four kinds of rice cultivars from shallow hill and deep hill rice were selected respectively according to the valley height. And the area of rice planting was obtained by ground sampling survey and Google Earth image interpretation in the same growing season as validation data. This result was used to evaluate the monitoring accuracy of rice planting area in the hilly region of Sichuan Province based on OLI fusion images. After orthophoto correction of OLI image,15 m panchromatic band image and30 m multispectral images were used to fusion to get 15 m resolution fusion image. And supervised the classification with maximum likelihood method to get the monitoring result.【Result】Compared with the quadrat verification data,the results of rice planting area monitoring based on OLI images with the same sample area showed that the average accuracy of the shallow hill area was 93. 7 %,the error range was 1 % to 8. 7 %. And the depth area was 92. 5 %,the error range was 1. 5 % to 15. 8 %.【Conclusion】According to the error range of the monitoring results in the shallow hilly area and the deep hilly area,with the increase of the valley height,the terrain tended to be complicated,the plot tended to be narrow and broken,and the uncertainty of the OLI image monitoring result increases. And in the same time,the accuracy of OLI image monitoring has a downward trend. This study provides a reference for improving the accuracy of OLI image monitoring of rice planting area in hilly areas of Sichuan province. [ABSTRACT FROM AUTHOR]

Self-reported surveys in media usage behavior have been conducted by many companies and institutions. However, whether such surveys accurately reflect the actual usage has rarely been discussed. In this study, we revealed the difference between self-reported survey and automatically collected behavior log for smartphone usage duration, and investigated the relationship of individual attributes to the difference. Though past studies focused on measures (frequency versus duration) or question formats (open-ended versus closed), we successfully reduced the difference by adopting questioning methodologies, i.e., recall aids and timetable. We found that; (1) smartphone usage duration tends to be underreported, (2) when reported results highly deviate from the log, applying recall aids and timetable questionnaire reduces the difference, and (3) the difference is affected by age, gender, full-time job, and leisure time. [ABSTRACT FROM AUTHOR]

The most important task of carrying out the research on land use/land cover changes is to obtain accurate land cover data timely and efficiently. In recent years, many researches have been carried out to improve the accuracy of land cover classification, but they mainly focused on the aspects of land cover classification methods, classification features, classification systems and reducing noise pollution of remote sensing images. There were also some researches in which time series NDVI (normalized difference vegetation index) was directly applied to classify land cover or detect change of land cover. However, the researches that enhance classification accuracy for low classification precision areas on the basis of the existing land cover products using time series NDVI have not been found yet. In this paper, Henan Province in central China was taken as the study area, the regions possessing low classification precision with the existing MODIS land cover product (MOD12Q1) were selected, and the study on improving classification accuracy in these regions was carried out by means of the construction of time series NDVI database and the measurement of similarity of time series NDVI curves. The results are as follows: 1) Time series NDVI is an important feature for land cover classification, and there is a strong correlation between time series NDVI and land cover categories. The overall accuracy of the land cover data extracted based on time series MODIS-NDVI database in the study area was as high as 79.57% (sample evaluation based on field survey) and 73.45% (comparative evaluation with land use map at scale of 1:100 000) respectively. It is demonstrated that it is feasible to improve the accuracy of land cover classification by means of time series NDVI. 2) It was shown from a practical application that classification accuracy of existing land cover products could be significantly improved by using time series MODIS-NDVI database. The overall classification accuracy of the new land cover product, which was obtained by revising original MCD12Q1 based on time series MODIS-NDVI database, increased by 10.29% (from 72.76% to 83.05%, comparative evaluation) and 17.20% (from 64.52% to 81.72%, sample evaluation) respectively. 3) Degree of accuracy improvement for various land cover categories was different. The producer's accuracy for forest land, grassland, cultivated land, artificial land surface and water body increased by 35.36%, 29.51%, 2.98%, 6.96% and 6.11% respectively. 4) With regard to 2 specific methods that were used for judging similarity of NDVI curves in time series, the minimum distance (MD) method is superior to spectral angle matching (SAM) method in general. In conclusions, it is an effective method of improving precision of existing land cover products to retain parts of land cover information with high precision and reclassify the parts with low precision using time series NDVI. The classification accuracy of land cover products can be significantly improved by revising them based on time series NDVI database. [ABSTRACT FROM AUTHOR]

As the most basic soil data, soil map plays an important role in the development and utilization of soil resources and in the construction of agricultural production. The soil map of the second national soil survey in China has been used as the basic data of soil in resources and environment management, global change research, eco hydrological simulation and other fields. But it is found that the classification accuracy of the second national soil survey on soil types and subtypes is not high. Moreover, with the continuous progress of the society, the more requirements for the accuracy and timeliness of soil maps are put forward by various undertakings, such as precision agriculture, environmental management, land management, eco hydrological simulation and so on. With the continuous development of remote sensing technology, remote sensing survey and mapping has gradually replaced some conventional soil surveys, and it has become one of the universal soil digital mapping methods. All the methods on remote sensing survey and mapping of soil types are based on the relationship between soil and environment, but the characteristics of soil environment in different regions and its extraction methods on remote sensing are different. In recent years, domestic and foreign experts have launched a lot of researches on remote sensing survey and mapping methods, but the research on the model and method for remote sensing survey and mapping of soil types and subtypes in semi-arid sand region have rarely reported. The purpose of this paper is to solve the problem of remote sensing survey and mapping of soil types and subtypes in semi-arid sand region. Based upon soil genesis theory and soil environment condition in semi-arid sand region, we took Horqin Left Back Banner as an example, analyzed the relationship between soil type distribution and environmental factors in semi-arid sand region with the method of field survey and expert knowledges. And then put forward a method for remote sensing survey and mapping of soil types or subtypes in semi-arid sand region based upon multi-temporal Landsat 8 OLI remote sensing images. The results indicated that remote sensing survey and mapping of major soil types or subtypes in semi-arid sand region, for example swamp soil, saline-alkali soil, meadow soil, aeolian sandy soil and their subtypes, could be realized with the help of the modified normalized difference water index (MNDWI), salt index (SI), normalized difference moisture index (NDMI) and normalized difference vegetation index (NDVI) extracting from multitemporal Landsat 8 OLI remote sensing images. Using the proposed method survey and mapping soil types and subtypes in Horqin Left Back Banner, and then used statistical methods to check the accuracy of digital mapping results by soil type data observed in the field. The results showed that the overall accuracy of digital mapping results took percentages of 72.84% and the Kappa coefficient was 0.7037. This study provides approaches and references for digital soil mapping in semi-arid sand region, and provides possibilities to solve the problem of low aging and low precision on sudden basic data in semi-arid sand area by using the method of digital soil mapping. [ABSTRACT FROM AUTHOR]

We present the principals for BDS and BDS/GPS real-time kinematic (RTK) positioning. A experiment was conducted on Songshan calibration field using a UAV-based low altitude photograph platform which carried a double frequency GNSS system simultaneously receiving BDS and GPS signals. By comparing the positioning result of GPS, BDS, and the BDS/GPS-combined RTK models, and using these three groups of camera exposure station coordinates to carry out GNSS-supported aerotriangulation. These experiments demonstrate that the performance of GPS, BDS and BDS/GPS-combined RTK positioning model are very close in bundle block adjustment. For all three groups, the overall root mean square error was all lower than±0.17 m for the planimetry and±0.25 m for height, which satisfies the Chinese National specifications of aerial photogrammetric 1:500 mapping in hilly regions. [ABSTRACT FROM AUTHOR]

Aiming at the problem of repeated positioning accuracy of the unloading robot, the parametric simulation analysis of the unloading robot under the joint condition of the three hinged parts was carried out. At the same time, the position and velocity of the unloading robot were respectively.And the acceleration of the three parts of the use of Pro/E three-dimensional modeling of the establishment of the physical model of tire unloading robot, through the Matlab program to get unloading robot hinge of the 1 000 group obey the normal distribution of random sampling data, and then the solid model and the obtained parameterized data was introduced into ADAMS for dynamic simulation analysis to obtain the movement curve and position change data of the unloading robot during the movement. Based on the Monte Carlo method, the probability of the dumpling gap was obtained by calculating the probability. The results indicate that there are some changes in position, velocity and acceleration in the case of hinge, and when the allowable deviation is -0.25 mm < μ < 0.25 mm, the reliability of the positioning accuracy of the tire manipulator can be guaranteed. [ABSTRACT FROM AUTHOR]

In order to further improve the accuracy, a forecasting method with combined residual error correction is used in this paper. Based on the forecasting method, the residual error correction model and its combination ways are analyzed among some single forecasting methods, and the very high accuracy of the combination method with two minimum relative prediction errors is proven within a certain period. And then one forecasting method with dynamical combined residual error correction is proposed, based on choosing two minimum relative prediction errors to form the correction model during different periods. A study case indicates that the combination ways proposed in this paper can further improve the accuracy of combination forecast. [ABSTRACT FROM AUTHOR]

Accurate structural parameters and crown characterization of large isolated apple trees were vital for adjusting spray doses, trimming, autonomous harvesting. According to previous research, canopy measurement methods to characteristic the whole tree structure could be classified in two groups: Manual measurements and electronic procedures to estimate tree dimensions. These methods were time consuming and required specialist knowledge, so a simpler crown characterization measurement method was required. Terrestrial laser scanning (TLS) could provide accurate canopy information through non-destructive methods, which filled the gap between tree scale manual measurements and large scale LiDAR measurements. Laser scanning delivers a dense cloud of points, and this raw point data were filtered for deriving a digital terrain model and subsequent fitting of a parametric stem model. In this study, Trimble TX8 had been used to getting point clouds of the apple tree canopy with trees height 3.2-5.1 m and 7 years old, in the orchard environment. A method and registration algorithm for reconstructing the three-dimensional (3D) apple tree canopy based on terrestrial laser scanner point cloud data from apple trees was presented. After an initial alignment had been obtained from this last set of correspondences, the object ball point clouds were extracted, and the noise was deleted by hands. In order to improve convergence speed, KD-tree improved ICP(iterated closest points), and combined with object ball, to estimate the optimal transform. The object residual errors and fitting errors at different distances between object and scanner were analyzed. Results showed that, the average residual errors was 1.3 mm, and the average fitting errors was 0.95 mm at the distance from 1 000 to 13 000 mm. All the errors were less than the traditional registration accuracy 5 mm. In addition, wind as an importance factor always influenced point clouds quality. In order to find the influence between them, several pieces of branches, apples and 80 pieces of leaves had been extracted in the wind speed from 0.9 to 4.5 m/s. And the branches and apple structures, the leaf characteristics were studied under different wind speed. Results showed that, the branches and apple outline clearly, both the single tree and group trees, the geometric parameters, such as apple diameter, stem diameter, trunk detection, canopy height, canopy diameter, planting distance, line spacing, could been extracted easily even if the average wind speed was 4.5m/s in the scanning instant. Great changes had taken place in the leaves edge and thickness, when the wind speed changed from 0.9 to 2.4 m/s. The thickness of the leaf profile had changed from 2.2 to about 35.8 mm, and the original point clouds Delaunay triangular mesh also became irregular. And long and narrow triangle appeared at the moment of the average wind speed 1.9 m/s. The three leaf thickness fitting curves, as quadratic curve, cubic curve and exponential curve, were in good agreements for the whole range of studied volumes (R2 =0.976, R2 =0.986 and R2 = 0.983, P < 0.001). The fitting curve showed that, apple canopy 3D point cloud data could be obtained with good quality in orchard environment. Comparing with the traditional manual measurement, the relative errors of the canopy parameter measurement values obtained from 3D point clouds data were less than 4%. [ABSTRACT FROM AUTHOR]

Currently, analysis centers (ACs) of International GNSS continuous monitoring and assessment system (iGMAS) could provide precise GNSS orbit products. To improve the stability and reliability of orbit products for high-precision users, we usually combine the orbit products from ACs. In this paper, we present a robust least square method of combing satellite orbits from different solutions. We first verify this method by combining GPS and GLONASS final orbit products provided by IGS Analysis Centers. Results show that the RMS differences between our combined GPS orbits and those from IGS are about 4 mm, and the RMS differences between our combined GLONASS orbits and those from IGS are about 5 mm. As the orbits of different IGS ACs are calculated in different reference frames, we first transform the orbits of different IGS ACs to the reference frame of IGS combined solution independent exchange format (SINEX) solutions before orbit combination. Results show that this transformation can improve the quality of combined orbits up to 2 mm. We then apply this method to analyze and combine GNSS satellite orbit products provided by ten of iGMAS ACs. For most iGMAS ACs, results show that the precision of GPS final and rapid orbits are better than 2.5 cm, and the precision of GPS ultra-rapid orbits are better than 6 cm and 15 cm for observed part and predicted part, respectively. The precision of iGMAS combined final orbits are 2 cm, 2~3 cm and 6 cm for GPS, GLONASS and Galileo satellites, respectively. The precision of iGMAS combined final orbits are 1.5 m and 20 cm for IGSO and MEO/IGSO of BDS, respectively. The relatively lower precision for combined GEO orbits is due to the different satellite antenna phase center offset (PCO) models adopted by different iGMAS ACs. [ABSTRACT FROM AUTHOR]

In the field of the precise underwater acoustics, the constant gradient ray-tracing method is the normal choice for positioning. But when the incidence angle is too large, the iteration of the incidence angle will diverge. In this paper, we analyze the reason behind this problem, and present a new iteration method for cases of large incidence angles. The key element of this method is to change the iteration parameter from the Snell refraction constant p to the radius of curvature R. We use simulation data to test the effectiveness of our method. The results show that when the incidence angle is not too large (e.g.≤80°), our new method and the original constant gradient ray-tracing method have the same accuracy, but when the incidence angle is large (e.g. >80°), the accuracy of our method is better than the original method. [ABSTRACT FROM AUTHOR]

This paper summarizes and reviews the freehand 3D ultrasound probe calibration techniques based on the optical tracking system. It firstly introduces the current researches on existing calibration methods and divides them into point phantom, line phantom, plane phantom, and method without phantom based on their principles. Then two approaches are introduced for determining the calibration matrix, including the iterative and the closed-form methods. Next two types of indexes for evaluating the precision and accuracy of a calibration transformation are introduced. At last the characteristics of various calibration methods are analyzed from perspectives of precision, accuracy, time, reliability, scope of application, and ease of use. The existing problems and trends of the freehand 3D ultrasound probe calibration are also discussed. [ABSTRACT FROM AUTHOR]

To solved the problem that nodes centrality ranking algorithm of networks worked badly in quality, this paper deve­loped an efficient algorithm based on network structure. This paper applied the random data to confirm the feasibility and validity and used the Perron-Frobenius Theorem to prove the convergence of the algorithm. Simulation experiments show that the algorithm is more effective than the compared ones in the precision and convergence. On the bases of nodes centrality ranking algorithm, this paper proposed the edges centrality ranking algorithm and then verified the validity. [ABSTRACT FROM AUTHOR]

Problems in the reservoir subdivision and correlation mainly display in two aspects: one is that the comparison results are usually lithologic units, which are often not isochronous; another one is that the accuracy of comparison result is not enough, which can not meet the needs of tapping the remaining oil in high water cut stage. The basic reasons are the limitation of the understanding of layer, stratum and the reservoir structures. Based on the traditional stratigraphic theories, the reservoir subdivision and correlation show that the layer and stratum structures accord with the “layer” mode, the layer distributes over the whole area, closing to the level and paralleling to each other, and the layers are stacked horizontally. However, the sequence stratigraphy, which breaks through the understanding of traditional stratigraphy, believes that the layer does not distribute over the whole area necessarily, not close to the level necessarily and not parallel to each other necessarily. The spatial position of layer varies greatly, and the superimposed relationships between layers can be overlap or offlap. Architectural-element analysis is more detailed to reveal the structural characteristics of the reservoir. The layer divided originally is a complex, which should be further divided hierarchically. Based on hierarchical interface division, the complex can be subdivided into a series of architecture units with different shapes and complex distribution. Beginning with the basic reason of problems, the corresponding countermeasure is proposed that taking the theories of sedimentology, sequence stratigraphy and seismic stratigraphy as guidance, the hierarchical interfaces are divided by the means of architectural-element analysis. [ABSTRACT FROM AUTHOR]

Atmospheric disturbance has a great influence on the measurement accuracy of Ground-Based SAR; thus the selection of a suitable atmospheric correction method is related to the reliability and accuracy of measurement results. A whole scene atmospheric correction method using the PS atmospheric correction network is proposed, and applied in a experiment monitoring a high-risk slope under construction. The effectiveness of the meteorological correction method proposed in this paper was verified by a comparison with the results of conventional atmospheric correction method and surveying robot. [ABSTRACT FROM AUTHOR]

In this paper, we propose a robust multi-quadric method (MQ-H) based on Huber loss function to conduct interpolations of contaminated spatial points, especially those derived from remote-sensing techniques. The objective function of the MQ-H has two main parts ; an improved Huber loss function and a regularized penalty term used to improve robustness and avoid overfitting, respectively. A mathematical surface, subject to model error with different distributions, was employed to comparatively analyze the robustness of the MQ-H, the classical MQ, and a least absolute deviation based MQ (MQ-L). The results indicated that when sample errors follow a normal distribution or a Laplacian distribution, the performance of MQ-H is comparatively better than those of MQ, and more accurate than MQ-L. For sample errors with a contaminated normal distribution and Cauchy distribution, MQ-H is more robust than MQ-L and MQ. Moreover, MQ with the improved Huber loss function is superior to MQ with the classical Huber loss function. A real-world example of DEM construction with stereo-image-derived elevation points indicates that compared to the classical interpolation methods including IDW (inverse distance weighting), OK (ordinary Kriging) and ANUDEM (Australian National University DEM), MQ-H has a better ability to reduce the impact of outliers while maintaining subtle terrain features suitable for qualitative analysis. [ABSTRACT FROM AUTHOR]

In order to provide a basis for the comparison, selection and determination of the appropriate burst pressure calculation formulas for steel spherical vessels, the indexes of accuracy and concentration for the precision evaluation of the calculation formulas were established. By means of 59 groups of measured data, the precisions of 4 different burst pressure calculation formulas were analyzed. The discussion gives conclusions as follow ： the formula's average accuracy ratio ( the ratio of the calculated burst pressure value to the measured value) and the coefficient of variation can be reasonably treated as the indexes of accuracy and concentration for the formula’s precision evaluation, respectively; for multi-layer spherical vessels, the average accuracy ratio of the mid-diameter formula is 0.977 0 and the coefficient of variation is 0.035 4, with the yield ratios of the vessel wall materials ranging from 0.720 9 to 0.847 5 and the diameter ratios ranging from 1.053 to 1.107； for single-layer spherical vessels, the average accuracy ratio of the mid-diameter formula is 1.169 1 and the coefficient of variation is 0.108 3, with the yield ratios of the vessel wall materials ranging from 0.336 2 to 0.618 9 and the diameter ratios ranging from 1.109 to 1.257； compared with the results out of the other 3 formulas, the burst pressures calculated with the mid-diameter formula for steel thin-walled multi-layer spherical vessels are more precise, the burst pressures calculated with the mid-diameter formula for steel thin-walled single-layer spherical vessels are more concentrated. [ABSTRACT FROM AUTHOR]

In geometrics, machine vision and other fields, the large rotation angle three-dimensional coordinate transformation often need to be applied based on the two corresponding point sets. The solving methods of the large rotation angle three-dimensional coordinate transformation are broadly divided into iterative methods and analytical methods. The iterative methods can obtain higher transformation accuracy. However, these methods depend on the initial value. In this contribution, quaternion is used to construct rotation matrix, a large rotation angle three-dimensional coordinate transformation formulae based on Newton iterative method is established, and a method which is widely used in guidance and control field for initial value calculation is given. Simulated and real data are used to validate the proposed algorithm, and the results are compared with those of other algorithms. The results show that the proposed algorithm makes the large rotation angle coordinate transformation model based on quaternion more robust. So the proposed algorithm is practically valuable for its stability of results, reliable accuracy and fast convergence. [ABSTRACT FROM AUTHOR]

In this paper, mode vectors via EOF (empirical orthogonal function) are obtained based on real sound velocity profiles; by correcting the terrain distortion, the reconstruction coefficients of sound velocity profile are determined by GA (genetic algorithm) and then the inversion result of sound velocity profile is obtained. Results show that terrain distortion caused by the sound velocity errors can be effectively corrected by the inversion result of sound velocity profiles. Meanwhile, the accuracy and processing efficiency of multi-beam bathymetry data was significantly improved. [ABSTRACT FROM AUTHOR]

The Moon is the brightest body in the night sky, and it is of great value to be used to determine the azimuth. However, the key problem is how to solve the center of the apparent Moon accurately. This paper puts forward a new method called spherical circle fitting algorithm to determine the center of the apparent Moon. It has such many merits as strictness, briefness and little calculation in contrast to the existing algorithm. Simulated observation data is processed to understand the relationship between the attitude of the phase of the Moon and fitting accuracy. An experiment based on real observations was used to testify the correctness of the algorithm, and a comparison is made between the spherical circle fitting algorithm and the old algorithm. The results show that while the inner precision is almost the same, the outer accuracy of our algorithm improves by 0.5″. These results suggest that spherical circle fitting algorithm is more suitable for engineering applications. [ABSTRACT FROM AUTHOR]

The basic principle of 3D laser scanner, and the test methods of its positional accuracy in pile surveying were introduced in this paper. According to engineering requirements, we arranged control points, chose columns under the viaduct in land as observation target, measured the center coordinates respectively using 3D laser scanner and total station, analyzed the measuring accuracy of 3D laser scanner based on total station measuring results, and explored its application in engineering surveying. [ABSTRACT FROM AUTHOR]