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Global registration method for multi-station point clouds based on the bundle adjustment method Qingzhou MAO, Mengxuan XIA, Qingquan LI, Jing ZHU, Tingli FAN Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1663-1670.   DOI: 10.11947/j.AGCS.2024.20240075 Abstract （368）   HTML （72）    PDF（pc） （8299KB）（348）       Knowledge map    Save In the extraction of parallelism and warping data for large-scale, high-density ice-making pipes, issues such as low detection accuracy and incomplete data coverage are prevalent. This paper proposes a method based on bundle adjustment for regional networks, utilizing a 3D laser acquisition approach with multi-prism target spheres. The target sphere centers are extracted using a radius-constrained random sample consensus (RANSAC) sphere fitting method. By applying coordinate transformations between the absolute coordinates of the station point cloud origins, the relative coordinates of the target centers, and the absolute coordinates of the target centers, a global solution for the positions and orientations of all stations is achieved using bundle adjustment. The method was validated using scan data from the National Speed Skating Oval. The results show that after point cloud matching, the internal consistency accuracy is 2.6 mm, and the external consistency accuracy is 1.9 mm, demonstrating higher acquisition accuracy compared to existing methods. Table and Figures | Reference | Related Articles | Metrics

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Six geographic application paradigms of big data Lun WU, Yuanqiao HOU, Yu LIU Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1465-1479.   DOI: 10.11947/j.AGCS.2024.20230199 Abstract （274）   HTML （54）    PDF（pc） （16210KB）（323）       Knowledge map    Save With the advent of the big data era, multi-source big data is on the rise, leading to the integration of data-driven research paradigms with geography. Geospatial big data based on individual behavior offers observations of massive individual behavior patterns, thereby achieving “from people to places” social perception and supporting various applications such as urban management, transportation, and public health. This article delineates six application paradigms focusing on geospatial big data from an application perspective, ranging from describing spatio-temporal distributions at a low level to optimizing spatial decision-making at a high level. The first direction involves a simple characterization of the spatio-temporal features of geographic phenomena and elements, while the second to fourth directions focus on exploring the rules and mechanisms behind spatio-temporal distribution characteristics. The last two directions provide support at the decision-making level. Furthermore, this article highlights issues in data acquisition, analysis methods, and application goals in big data applications. Table and Figures | Reference | Related Articles | Metrics

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Multi-star tracker angular velocity reconstruction method considering temperature effect correction Danyi HU, Yunlong WU, Yun XIAO, Yue QIU, Xiaohui WU, Yulong ZHONG Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1748-1760.   DOI: 10.11947/j.AGCS.2024.20240093 Abstract （238）   HTML （44）    PDF（pc） （10506KB）（162）       Knowledge map    Save High-precision satellite attitude control is an important data preprocessing aspect of satellite gravity mission operation. The key payload star trackers onboard the gravity field and steady-state ocean circulation explorer (GOCE) satellite inevitably experience temperature variations in its low orbit, leading to inter-boresight angles (IBA) deviations ranging from 2 to 14 arcseconds, directly impacting the accuracy of satellite attitude. Quantitative analysis of temperature effects on satellite attitude and precise determination of satellite angular velocities are essential steps in the satellite data preprocessing workflow, directly influencing the accuracy of high-precision gravity gradient component reconstruction. In this study, based on the characteristics of the GOCE satellite mission, we develop a temperature effect correction method for joint attitude quaternion reconstruction using multiple star trackers. This method involves constructing a linear function of temperature-related relative attitude offsets between star trackers, establishing a weighted matrix considering the precision differences among sensor axes, and obtaining the optimal quaternion reconstruction of attitude velocities based on the principle of least squares. Additionally, in the original attitude data processing, we propose a logarithmic quaternion Hermite hypersurface interpolation method for data optimization. The research results demonstrate that the corrected attitude quaternions calculated from star tracker data exhibit no significant deviation when compared with reference frame information. Moreover, after temperature effect correction, the noise level of angular velocity for each tracker axis significantly decreases by approximately two orders of magnitude, achieving an accuracy of 10-10 rad·s-1 and significantly improving the precision of velocity reconstruction. Additionally, the angular velocity accuracy of each tracker axis maintains good consistency.The power spectral density of the gravity gradient trace calculated based on this method shows a more significant improvement in the whole frequency domain. Table and Figures | Reference | Related Articles | Metrics

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Rapid single point positioning enhancement service and application based on urban CORS Yang LIU, Guang YANG, Xiaohui CHENG, Xiao ZHANG Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1706-1714.   DOI: 10.11947/j.AGCS.2024.20240077 Abstract （208）   HTML （25）    PDF（pc） （8322KB）（126）       Knowledge map    Save In the realm of smart city development, the scalability, privacy, and heightened reliability of CORS (continuously operating reference station) location services have emerged as pivotal focal points. This paper presents an innovative urban CORS augmented positioning service leveraging PPP-RTK (precise point positioning-real-time kinematic) technology. It delineates the formulaic methodology for achieving enhanced precision single-point positioning within urban environments, elucidating the estimable parameters essential for urban CORS augmented positioning and their practical implementation on client platforms. Through integration with real-time data sourced from the Guangzhou CORS network, the efficacy of the PPP-RTK service is rigorously evaluated. Test results demonstrate that the initial epoch of the PPP-RTK client plane rapidly converges to centimeter-level accuracy, with vertical elevation convergence achieved within approximately seven epochs. Furthermore, the performance of the enhanced positioning parameter SSR2OSR (state space representation to observation space representation) in PPP-RTK is found to be comparable to that of short baseline RTK solutions, thus substantiating its capacity to cater to the monitoring requirements of a substantial user base. On-board experiments exhibit superior 3D accuracy, surpassing lane-level precision by a margin of less than 0.5 meters, underscoring the capability of PPP-RTK positioning to fulfill the stringent reliability criteria essential for various positioning applications. Table and Figures | Reference | Related Articles | Metrics

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3D Gaussian radiation field modeling for real-scene bridges Wei MA, Qiang TU, Jianping PAN, Lidu ZHAO, Wei TU, Qingquan LI Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1694-1705.   DOI: 10.11947/j.AGCS.2024.20240071 Abstract （207）   HTML （26）    PDF（pc） （25350KB）（280）       Knowledge map    Save Realistic 3D modeling and digital twins have become essential foundations for bridge operation and management. However, given the complex geometric structures of bridges, current 3D modeling methods face issues such as large amounts of raw data collection, low modeling efficiency, and missing or deformed model details. In response to these challenges, this paper investigates a bridge realistic 3D reconstruction method based on 3D Gaussian radiance fields. This method utilizes 3D Gaussian functions to construct a Gaussian radiance field from sparse point clouds generated by captured images. Adaptive optimization of radiance field parameters is performed based on stochastic gradient descent, and real-time visualization of the 3D model is achieved through differentiable rasterization, resulting in high-quality bridge 3D reconstruction and rendering. The study explores the impact of different image resolutions and various parameter changes on bridge modeling. Comparisons with traditional methods are made to provide theoretical and technical support for further bridge applications, promoting efficient and accurate realistic 3D reconstruction of complex bridge structures. Table and Figures | Reference | Related Articles | Metrics

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Underwater photogrammetry positioning of immersed tunnel element interfacing Lin TIAN, Qingquan LI, Huachuan MA, Biao XUE, Minglei GUAN, Dejin ZHANG Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1671-1678.   DOI: 10.11947/j.AGCS.2024.20240030 Abstract （187）   HTML （26）    PDF（pc） （7594KB）（144）       Knowledge map    Save Using a measurement tower to convert underwater positioning to above-water positioning is the main method for positioning submarine tunnel segments at home and abroad. However, the coupled effects of measurement tower deformation and segment deformation affect positioning accuracy and are unable to adapt to deep-water docking. This article proposes an underwater active light encoding cooperative target photogrammetry segment docking positioning method, which uses active light to increase the optical distance, suppress backscattering, and encode the target to overcome the influence of suspended particles and plankton. Combined transmission light separation imaging and refractive index as unknown parameter measurement adjustment, overcoming the influence of water body turbidity and refractive index induced optical distortion on underwater photogrammetry. A photogrammetry system is installed on the top of the approaching segment's docking end, and a cooperative target is installed at the corresponding position of the already-submerged segment to ensure measurement and determine its position and attitude in the construction coordinate system. The position of the approaching segment in the construction coordinate system is obtained through rear intersection calculation, and the positional and attitude adjustment information of the segment is generated by comparing it with the theoretical position it needs to be sunk to, which assists in docking. The application of this method in the Deep Channel and Dalian Bay Submarine Tunnel projects shows that the segment docking linear accuracy reaches 2 cm and 100 m, providing key technical support for the construction of submarine tunnels under deep-water conditions in the future. Table and Figures | Reference | Related Articles | Metrics

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Weakly supervised building change detection integrating multi-scale feature fusion and spatial refinement for high resolution remote sensing images Xin YAN, Li SHEN, Junjie PAN, Yanshuai DAI, Jicheng WANG, Xiaoli ZHENG, Zhi-lin LI Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1586-1597.   DOI: 10.11947/j.AGCS.2024.20230118 Abstract （182）   HTML （33）    PDF（pc） （20867KB）（175）       Knowledge map    Save To alleviate the heavy dependence of deep learning methods on large-scale high-cost pixel-level annotations, in this paper, we propose a novel weakly supervised method, named MDF-LSR-Net, for high-resolution remote sensing building change detection. Specifically, the proposed method first designs a multi-scale difference feature aggregation module to make better use of multi-scale difference features to generate change heatmaps. Then, by utilizing the local spatial consistency of the low-level fused difference features, MDF-LSR-Net presents a local spatial refinement module to enhance the integrity and accuracy of change regions in heatmaps. Finally, the change detection model is trained based on the high-quality change heatmaps. Experimental results on publicly available datasets, including WHU and LEVIR, demonstrate that our proposed method can obtain more integral and accurate change heatmaps, leading to significantly improved detection performance of the final change detection model. The final model has achieved over 65% points in IOU and over 79% points in F1 on the WHU dataset. Table and Figures | Reference | Related Articles | Metrics

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The transformation of the scientific concept of GIS: from Map-based GIS to Space-oriented GIS Renzhong GUO, Yebin CHEN, Zhigang ZHAO, Ding MA, Biao HE, Weixi WANG, Wuyang HONG, Minmin LI Acta Geodaetica et Cartographica Sinica    2024, 53 (10): 1853-1862.   DOI: 10.11947/j.AGCS.2024.20240152. Abstract （176）   HTML （43）    PDF（pc） （12116KB）（298）       Knowledge map    Save From the 1960s to the present, GIS has undergone a development journey of over 60 years, during which its connotations have evolved from geographic information system (GISystem) to geographic information science (GIScience), and further to geographic information service (GIService). During this period, GIS research has primarily been based on the two-dimensional abstract expression logic of cartography (Map-based GIS), achieving abstract analysis and representation of the real world. However, with the continuous emergence of new technologies and new demands such as 3D real scene, digital twins, and city information modeling (CIM), the original two-dimensional logic of GIS is facing challenges in the collection, processing, and fusion of multi-source heterogeneous spatiotemporal big data, the representation of complex spatiotemporal dynamic processes, and the mining of potential spatiotemporal patterns. How to adjust the scientific positioning of GIS to adapt to the multi-type, multi-level, and multi-role needs of spatial object expression and analysis in the digital society has become an important issue that GIS development urgently needs to consider. From a methodological perspective, we deeply analyzes the bottlenecks of Map-based GIS in spatial representation, spatial analysis, and comprehensive application. Furthermore, based on the development needs of GIS in the new era, we propose a scientific concept transformation model from Map-based GIS to Space-oriented GIS, integrating the logical thinking of Map-based GIS from the perspectives of theoretical foundations, management models, visualization forms, and functional positioning, and innovative applications under the transformation of GIS scientific concepts. This research aims to provide reference ideas for the development of GIS in the new era. Table and Figures | Reference | Related Articles | Metrics

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An intelligent classification method for building shape based on fusion of global and local features Fubing ZHANG, Qun SUN, Jingzhen MA, Shijie SUN, Bowei WEN Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1842-1852.   DOI: 10.11947/j.AGCS.2024.20240040 Abstract （169）   HTML （19）    PDF（pc） （7892KB）（117）       Knowledge map    Save Supported by deep learning methods for building shape cognition, it has become a hot research topic in fields such as cartography. The feature mining ability of deep learning can help extract embedded representations of shapes, supporting application scenarios such as cartographic generalization and spatial retrieval. A graph convolutional neural network model for building shape classification that integrates global features and graph node features is constructed, and validated using building data as an example. Firstly, a weighted building graph is constructed, and then a fusion description of the shape is generated based on the 4 macroscopic shape features of building and the multi-level local and regional structural features of boundary vertice. Graph convolutional neural networks are used to extract multi-level shape information, and the feature coding generated by fusing graph representations from different layers is used for shape classification.The experimental results show that compared to the comparative method, the proposed method is more effective in distinguishing the shape categories of different buildings, and the generated feature coding have positive shape discrimination. Table and Figures | Reference | Related Articles | Metrics

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Remote sensing image stripe noise removal model based on detail information constraints Mi WANG, Tengteng DONG, Tao PENG, Shao XIANG, Qiongqiong LAN Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1799-1816.   DOI: 10.11947/j.AGCS.2024.20230363 Abstract （162）   HTML （20）    PDF（pc） （33613KB）（248）       Knowledge map    Save Remote sensing images are often contaminated by stripe noise during the acquisition process, which reduces the visual effect of remote sensing images and has an adverse effect on image interpretation and inversion. Although some mainstream stripe noise removal methods based on variational methods can remove stripe noise, they often lead to serious loss of image detail information. Based on the above problems, this paper proposes a remote sensing image stripe noise removal model DISUTV based on detail information constraint. In the DISUTV model, the proposed detail information separation operator based on bilateral filter and orthogonal subspace projection is effectively combined with one-way total variation regularization term, group sparsity regularization term and one-way total variation regularization constraint term, and the alternating direction multiplier method is used to solve it, which is used to obtain high-precision stripe noise without detail information from stripe noise images. The stripe noise removal ability, detail information retention ability and robustness of the algorithm are verified using simulated data and real data, and compared with existing cutting-edge methods. Experimental results show that the proposed method can better retain the detail information of the image while removing stripe noise, and presents good qualitative and quantitative results. Table and Figures | Reference | Related Articles | Metrics

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Research on knowledge extraction from street scene images based on hybrid intelligence Wanzeng LIU, Hang CHEN, Jiaxin REN, Zhaojiang ZHANG, Ran LI, Tingting ZHAO, Xi ZHAI, Xiuli ZHU Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1817-1828.   DOI: 10.11947/j.AGCS.2024.20220720 Abstract （158）   HTML （33）    PDF（pc） （11943KB）（159）       Knowledge map    Save This study presents a hybrid intelligence-based approach, named K-CAPSNet, for extracting knowledge from streetscape images. To tackle the challenge of intelligent extraction of streetscape image objects, we develop a panoramic segmentation network with a joint attention mechanism that integrates both channel information and spatial information of streetscape images. This improves the object segmentation accuracy. Additionally, we incorporate streetscape knowledge, which is formed by people in production and life, into the streetscape image cognition process. We set the object marking threshold using a priori knowledge to optimize the segmentation results. Moreover, we utilize the a priori knowledge of streetscape images to verify the topological relationship between streetscape objects and to mine spatial relationship knowledge using depth information. Finally, we employ semantic templates to describe and express the type, number, and spatial relationship between streetscape objects. The experimental results demonstrate that our method outperforms the baseline network and significantly improves the quality of panoramic segmentation and recognition, thereby achieving better extraction and expression of the knowledge of streetscape images. Table and Figures | Reference | Related Articles | Metrics

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An innovative millimeter-level positioning method for multiple millimeter wave radar network in tunnel environment Yinzhi ZHAO, Jingui ZOU, Xiaoxi ZHANG, Ze WANG, Xinzhe WANG Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1679-1693.   DOI: 10.11947/j.AGCS.2024.20230352 Abstract （147）   HTML （23）    PDF（pc） （12586KB）（140）       Knowledge map    Save With the arrival of the intelligent safety monitoring era, research on monitoring point positioning measurement in tunnels and mines is gradually developing towards all-time and all-weather aspects. In response to the problems of poor real-time performance and long measurement period in tunnel monitoring point positioning, as well as susceptibility to factors such as dust and lighting, this paper introduces millimeter wave radar with high distance and speed resolution to conduct high-precision positioning research for tunnel monitoring points. An innovative millimeter-level positioning method for tunnel environment based on multiple millimeter wave radars network is proposed. Firstly, based on the traditional fast Fourier transform to extract ranging information, a method is proposed to refine the frequency spectrum using chirp-Z transform. This method can optimize the ranging observations and ensure ranging accuracy at the millimeter level. Secondly, due to the drawback that traditional ranging radars can only obtain one-dimensional radial deformation, multiple millimeter radars network method is introduced. Further, a functional model for multi machine network positioning is established. In addition, a random model is proposed that takes into account the difference of each millimeter wave radar in radar pulse observation accuracy of each epoch and prior distance. Finally, the precision of ranging and positioning is verified through tunnel tests. The results show that, the phase difference method based on chirp-Z transform proposed in this manuscript can achieve ranging precision within 0.3 mm, and the computational efficiency of the algorithm is improved by 50 times compared to the existing method. When the target to be monitored is stable, the precision of X, Y and Z directions is 2.7 mm, 0.6 mm and 6.6 mm. However, the elevation direction precision is slightly lower due to the influence of tunnel height. In the case of micro movement of the target to be tested, this proposed method can detect small deformations. The method proposed in this manuscript meets the requirements of monitoring point real-time positioning in tunnel environment for all time, high accuracy, and long periods. Furthermore, it is expected to be applied in industrial structure deformation monitoring. Table and Figures | Reference | Related Articles | Metrics

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Spatio-temporal anomaly detection: connotation transformation and implementation path from data-driven to knowledge-driven modeling Yan SHI, Da WANG, Min DENG, Xuexi YANG Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1493-1504.   DOI: 10.11947/j.AGCS.2024.20230341 Abstract （141）   HTML （5）    PDF（pc） （8281KB）（148）       Knowledge map    Save As one of the critical technologies of geo-spatial data mining, spatio-temporal anomaly detection has the capacity of providing key breakthroughs for deeply revealing the evolution mechanism of geographic processes. Promoted by the big data and artificial intelligence technology, the transformation from data-driven to knowledge-driven modeling is the development tendency for the intelligent detection of spatio-temporal anomalies from geographic big data. This paper systematically sorts out the development process and the mainstream study ideas of current spatio-temporal anomaly detection. Through analyzing the dialectical relationships among data, information and knowledge, a unified description framework of spatio-temporal knowledge is constructed by integrating geographic variables, space basis, spatio-temporal relationships and knowledge types. Then, the connotation of bidirectional driving between spatio-temporal knowledge and spatio-temporal anomalies is elaborated with the help of practical cases. The implementation path for intelligent detection of spatio-temporal anomalies is further proposed, which includes spatio-temporal knowledge correlation modeling, spatio-temporal anomaly intelligent detection and spatio-temporal anomaly-based knowledge dynamic updating, so as to support both the reliable spatio-temporal anomaly detection and the credible spatio-temporal knowledge services. Reference | Related Articles | Metrics

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Vectorized integrity monitoring method for PPP-RTK correction products Liang LI, Liuqi WANG, Ningbo WANG, Min LI, Zishen LI, Fengze DU, Shuai PANG, Zhibo NA Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1777-1789.   DOI: 10.11947/j.AGCS.2024.20230475 Abstract （139）   HTML （11）    PDF（pc） （10772KB）（112）       Knowledge map    Save PPP-RTK correction products serve as fundamental information for achieving the satellite navigation-based positioning with high-precision and rapidly convergence simultaneously. Integrity monitoring is a core requirement for ensuring the reliability of PPP-RTK positioning. The traditional integrity monitoring methods for PPP-RTK correction products suffer from the lack of the monitoring risks allocation tree and the low sensitivity in monitoring multiple faults. These shortcomings cause a decreased availability of the PPP-RTK correction products. In this contribution, a vectorized integrity monitoring method is proposed for PPP-RTK correction products. Based on the minimum protection level criteria, the integrity and continuity risk of PPP-RTK correction products has been allocated. A sequential pre- and post-broadcasting loopback monitoring architecture has been developed in the range domain and the position domain, respectively. The proposed method, implemented with carrier phase observations, incorporates vectorized classification and monitoring, along with the executive monitoring the results of multiple stations. The proposed vectorized integrity monitoring method enhances the sensitivity and availability of the integrity monitoring for PPP-RTK correction products. Analysis of simulation and real-world data indicates that the proposed method outperforms traditional methods in both sensitivity and availability, achieving at least 99% of availability. Table and Figures | Reference | Related Articles | Metrics

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A RSSI ranging algorithm based on GWO-BP neural network Yiruo LIN, Kegen YU, Feiyang ZHU, Jinwei BU Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1564-1573.   DOI: 10.11947/j.AGCS.2024.20220693 Abstract （127）   HTML （13）    PDF（pc） （6763KB）（78）       Knowledge map    Save Recently, the research on received signal strength indication (RSSI) based ranging has received a significant attention, especially in the field of Internet of things and indoor positioning. Precise distance measurement is the basis for high-precision positioning based on ranging algorithms, but the RSSI signal is highly fluctuating due to measurement noise and multi-path effects, which leads to a non-uniform mapping relationship between RSSI and the real physical distance in space. In order to enhance the mapping relationship between RSSI and real physical distance and improve the precision of RSSI ranging, this paper proposes a RSSI ranging algorithm based on GWO-BP neural network, which makes use of back propagation (BP) neural network and gray wolf optimization (GWO) algorithm. GWO algorithm has faster convergence and greater stability than particle swarm optimization (PSO), genetic algorithm (GA), differential evolution (DE), evolutionary programming (EP) and evolution strategy (ES). Furthermore, in this paper, the results of the experiments conducted in two different environments by collecting real data through the developed smartphone software show that: the root mean square error (RMSE) of the path loss model (PLM) based ranging were 2.218, 2.059 m, the RMSE of the traditional BP neural network ranging algorithm were 1.541, 1.551 m, and the RMSE of the GA algorithm-based optimized BP neural network ranging algorithm were 1.269, 1.201 m, respectively, and the RMSE of the GWO-BP neural network ranging algorithm proposed in this paper were 1.054, 0.833 m, respectively. The results indicate that the RSSI ranging algorithm proposed in this paper has higher ranging precision and better robustness. Table and Figures | Reference | Related Articles | Metrics

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Construction of series ultra-high-degree Earth's gravity field models DQM2022 and their precision evaluation Yunpeng WANG, Xiaogang LIU, Qi LI, Duan LI, Liu FANG Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1505-1516.   DOI: 10.11947/j.AGCS.2024.20230530 Abstract （123）   HTML （19）    PDF（pc） （7736KB）（107）       Knowledge map    Save Based on ellipsoidal harmonic analysis, the regional integral correction iteration method and the global integral correction iteration method for construction of ultra-high-degree Earth's gravity field model (EGM) are proposed in this paper. The limitations of the traditional regional integral correction method are solved, and the precision of the improved EGMs applied in China is effectively improved. Taking EGM2008 and EIGEN-6C4 EGMs as the initial models, and series ultra-high-degree EGMs DQM2022 are constructed based on the latest 5′×5′ measured grid mean gravity anomaly data in China and its surrounding areas, and their complete degree and order is 2190. The precision of improved EGMs are evaluated by measured gravity anomaly on the ground, GNSS/leveling and astrogeodetic vertical deflection. The results show that the precision of the improved EGMs are significantly improved when indicating the gravity field in China, compared with the initial models, i.e., the precision of gravity anomaly, elevation anomaly, and vertical deflection are improved by 2.4~2.8 mGal, 1.0~2.4 cm, and 0.07″~0.15″, respectively. When indicating the gravity field in China, the improved EGMs based on the EIGEN-6C4 initial model have the highest precision, the precision of elevation anomaly and vertical deflection are about 10.6 cm, and 2.1″, respectively. Table and Figures | Reference | Related Articles | Metrics

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Measurement field error analysis and on site evaluation method for binocular stereo industrial photogrammetry system Dan ZHANG, Weifeng WANG, Guiping HUANG, Xinping WANG, Yanrong LIU, Zhanghong ZHAO Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1725-1736.   DOI: 10.11947/j.AGCS.2024.20220711 Abstract （121）   HTML （10）    PDF（pc） （8794KB）（84）       Knowledge map    Save In response to the issue of mismatch between nominal accuracy and actual measurement accuracy in different application scenarios of the binocular stereo industrial photogrammetry system, in-depth research was conducted on the mesh structure of it. It has been found that if the intersection angle of the measurement points is large than 45°, the horizontal angle between measurement points and baseline among 28°and 68°, vertical viewing angle less than 23 °, and the distance between the measure points and the baseline among 0.4B and 1.3B, the measure points' accuracy is high. If the measure points out of this range, the uncertainty of the points measurement will increase. Based on the above conclusions, a method has been proposed that use a binocular stereo industrial photogrammetry system to measure the length of a scale-bar at specified positions within the measurement field. By comparing the difference between the measured values of the scale-bar and the nominal value, the accuracy of the system's measurement field can be quickly evaluated. Experiments have shown that this method can quickly and accurately evaluate the measurement field accuracy of the binocular stereo industrial photogrammetry system, which plays an important guiding role in ensuring the quality of on-site operations and improving the efficiency of on-site operations. Table and Figures | Reference | Related Articles | Metrics

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A fast method for interpolation of the associated Legendre functions and its application to the calculation of local hexagonal grid point gravity anomalies using an ultra-high-degree gravity field model Xinxing LI, Haopeng FAN, Hongfa WAN, Diao FAN, Jinkai FENG Acta Geodaetica et Cartographica Sinica    2024, 53 (9): 1737-1747.   DOI: 10.11947/j.AGCS.2024.20230110 Abstract （120）   HTML （14）    PDF（pc） （9016KB）（82）       Knowledge map    Save In view of the low efficiency of the calculation of ultra-high-degree spherical harmonic synthesis for non-equal latitude distributed points of regional area, this article has conducted a deep research on the interpolation algorithm of associated Legendre functions. Combined with the harmonic expansion of the model gravity anomaly, a fast calculation method using interpolation was proposed for ultra-high-degree model free-air gravity anomaly. In order to verify the advantages of this new method over point sets with narrow distribution from east to west, the efficiency of the new method was further improved by adopting the spherical harmonic rotation(SHR) technology. The experimental results showed that the proposed method using interpolation reduced the calculation time from 3 669.41 s to 98.05 s compared with point-by-point approaches, with errors not exceeding ±0.005 mGal, when we used EGM2008 model up to 2160 degree and order to achieve the model free-air gravity anomalies of 30 303 hexagonal grid points at the same height level in Japan with non-equal latitude distribution. Meanwhile, by applying SHR and rotating these points distributed in the north-south direction to the east-west direction, the time consumption for the corresponding solution was further reduced from 98.05 s to 19.06 s, with a speed-up ratio of nearly 200 times to the original method. The method proposed in this article effectively solves the problem of low efficiency in solving ultra-high-degree model free-air gravity anomalies for regional non-equal latitude distributed points, and has a higher computing speed-up effect in the case of east-west elongated distribution. Table and Figures | Reference | Related Articles | Metrics

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Research on GNSS tropospheric delay modeling and spatial-temporal characteristics analysis of bias Junsheng DING Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1659-1659.   DOI: 10.11947/j.AGCS.2024.20230177 Abstract （119）   HTML （21）    PDF（pc） （1113KB）（79）       Knowledge map    Save Reference | Related Articles | Metrics

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Research on ambiguity resolution of INS-aided high-precision GNSS in urban environment Chao CHEN Acta Geodaetica et Cartographica Sinica    2024, 53 (8): 1662-1662.   DOI: 10.11947/j.AGCS.2024.20230223 Abstract （118）   HTML （19）    PDF（pc） （1182KB）（82）       Knowledge map    Save Reference | Related Articles | Metrics