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    18 August 2025, Volume 54 Issue 7
    Geodesy and Navigation
    Monitoring method of Earth's center of mass, figure pole and various rotational dynamics parameters
    Chuanyin ZHANG, Wei WANG, Tao JIANG
    2025, 54(7):  1157-1169.  doi:10.11947/j.AGCS.2025.20250141
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    The Earth's center of mass and figure pole are geodetic datum for describing and measuring the rotation of the Earth. The inability to accurately measure mass redistribution within the Earth's interior and geomaterial motion results in more uncertainties in geophysical excitations estimated from geophysical fluid data, thereby limiting in-depth investigations into the rotational dynamics of the Earth. In this paper, various geodetic measurements and Earth rotation motion are unified in an only Earth-fixed reference system, and the effects of Earth's figure polar shift and rotation variation on various geodetic elements are investigated. And then a time-synchronized monitoring methodology for Earth's figure pole and various rotational dynamic parameters is present by multi-geodetic collaboration, which can provide more favorable scientific and technological conditions for the in-depth study of the excitation dynamics mechanism of the Earth's rotation and the interaction of the Earth's spheres. The paper presents the following main results. ① The theoretical method for positioning of Earth's center of mass and figure pole is derived by space geometric and physical geodetic collaboration, which can not only accurately measure the variation time series of Earth's center of mass and figure pole, but also position and orient the current terrestrial reference system to the mean center of mass and mean figure pole in a specified time period. ② This paper presents the monitoring algorithms of the Earth's center of mass, figure pole and various rotational dynamics parameters by collaborating with the Earth's satellite observation, VLBI kinematics measurement, and the site's radial placement and gravity variation observations, which can improve the constraints of the study on the mechanism of the Earth's rotational dynamics.

    GNSS pseudo trigonometric leveling method
    Jianzhang LI, Haowen YAN, Weifang YANG, Xiaoning SU
    2025, 54(7):  1170-1177.  doi:10.11947/j.AGCS.2025.20250020
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    A GNSS pseudo trigonometric leveling method is proposed to address the issue of low accuracy in traditional total station trigonometric leveling. This method requires the deployment of a certain number of auxiliary points around the measurement station, the establishment of a zenith direction (opposite direction of vertical line) baseline vector using a precision level and GNSS receiver, and the replacement of the traditional total station line of sight with the GNSS baseline vector. The zenith distance of the target point is obtained through the vector dot product formula, and then the trigonometric leveling measurement value between two points is obtained. GNSS pseudo trigonometric leveling does not require two-point visibility and is not affected by atmospheric refraction, making it particularly suitable for long-distance elevation transmission across obstacles such as rivers, lakes, and valleys. A comparative experiment was conducted on a 3.8 km leveling route using precision leveling measurement and GNSS pseudo trigonometric leveling round-trip measurement. The experimental results showed that the difference between the two methods was less than the second-order leveling detection limit of 11.7 mm.

    Wide area coastal subsidence monitoring and driver analysis with multi tracks of TS-InSAR—a case study of Shandong province
    Peng LI, Jianbo BAI, Zhenhong LI, Houjie WANG
    2025, 54(7):  1178-1191.  doi:10.11947/j.AGCS.2025.20250061
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    Coastal subsidence will exacerbate relative sea level rise and increase the risk of flood-related coastal infrastructure inundation and soil salinization. As a major economic province in the east coast of China, the coastline of Shandong accounts for about 1/6 of the country. However, the spatiotemporal evolution characteristics and key drivers of land subsidence in Shandong are still unclear. In this paper, we conducted multi-track radar interferometry (InSAR) time series analysis with the Sentinel-1 imagery from 2019 to 2022. Firstly, we proposed a multi-track InSAR uncontrolled splice method applicable to the interface region between land and sea to correct the systematic bias of interferograms from adjacent tracks. Then, we generated a large-scale land subsidence rate map of the whole province with good consistency. Furthermore, we found multiple sinking funnels over 50 mm/a. Based on Sentinel-2 multispectral remote sensing images, deformation time series and principal component analysis, we revealed the spatiotemporal change of the heterogeneous sedimentation funnel and its drivers. The results show that human activities related to groundwater pumping and coal mining are the main factors causing land subsidence in Shandong province. This study is expected to provide technical support and scientific basis for large-scale coastal subsidence monitoring and risk management, and further improve the understanding of coastal geological disaster risk.

    A method for constructing a hydrological drought index integrated with GNSS and meteorological data
    Qingzhi ZHAO, Lulu CHANG, Yibin YAO, Haojie LI
    2025, 54(7):  1192-1205.  doi:10.11947/j.AGCS.2025.20250119
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    Hydrological drought events significantly impact socioeconomic development and ecosystem stability. Current hydrological drought studies often focus solely on changes in either surface or groundwater resources. To address this limitation, this study proposes a novel method for constructing a hydrological drought index, termed the GNSS cooperated with water balance principle hydrological drought index (GWHDI). This index integrates changes in both surface and groundwater resources based on the water balance principle. Specifically, vertical crustal displacement (VCD) derived from global navigation satellite system (GNSS) is used to reflect groundwater changes, while the combined temporal variability of precipitation and potential evapotranspiration serves as a surface water indicator. Additionally, multichannel singular spectrum analysis (MSSA) is employed to determine the optimal weights for different hydrological variables. The method was tested using data from 302 GNSS stations in the northwestern native United States from 2006 to 2020. The standardized runoff index (SRI) was used as a reference, and comparisons were made with the GNSS-based hydrological drought index (HDI) and the drought severity index (DSI). Results indicate that the GWHDI shows strong consistency with the SRI across different spatial and temporal scales, with average temporal and spatial correlations of 0.71 and 0.52, respectively, which are significantly better than those of HDI and DSI. Furthermore, the GWHDI reaches its minimum in summer, indicating a higher likelihood of hydrological drought during this period. These findings demonstrate that the proposed GWHDI is robust and reliable, offering a new approach for regional water resource management and hydrological drought monitoring and early warning.

    Pearson correlation coefficient time delay estimation applied in acoustic orientation
    Huiwen HU, Cong SHEN, Lintao LIU, Guocheng WANG
    2025, 54(7):  1206-1214.  doi:10.11947/j.AGCS.2025.20240406
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    To address the problems of unreasonably reflecting the correlation between two signals and edge effects in the generalized cross correlation-PHAT (GCC-PHAT), which lead to inaccurate time delay estimation (TDE), low-precision TDE, in-ability to orientate targets, et al, a method for the TDE based on the Pearson correlation coefficient (PCC) was proposed in this paper. The method uses the PCC to measure the correlation between two signals in a reasonable, accurate, and absolute manner. It shifts the observation signal, calculates the sliding PCC with the reference signal, and finds the position of the peak of absolute values to estimate the time delay. Simulation experiments show that compared to the GCC-PHAT, the proposed method improves the effective value ratio of the TDE by 14.67%, the precision of the TDE by 92.67%, and the precision of target orientation by 88.24%. Applying the method in a microphone array directional drone experiment, results further verify the high robustness and precision of the proposed method in the TDE; and compared to the GCC-PHAT, the proposed method improves the stable points ratio of target direction by 28.66%.

    Photogrammetry and Remote Sensing
    Farmland-parcel-based crop remote sensing classification method in complex mountainous areas via coupling spatial distribution patterns
    Tianjun WU, Manjia LI, Jiancheng LUO, Ziqi LI, Xiaodong HU, Lijing GAO, Zhanfeng SHEN
    2025, 54(7):  1215-1229.  doi:10.11947/j.AGCS.2025.20240440
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    Parcel-wise crop spatial distribution maps are currently in urgent need for precision agriculture applications. However, in mountainous areas with undulating topography, fragmented farmland structure, diverse crop types, and rainy climates, existing data-driven models may not fully satisfy the precision demands. Fundamentally, the causes may lie in the cognitive limits of the complicated agricultural systems and the uncertainty in remote sensing imaging, as well as the ignorance of spatial-temporal effect within the calculation. In response, this research focuses on the uncertainty reduction of remote sensing crop mapping, conducting researches on the introduction of spatial patterns to both the object-level decomposition of the targeted planting area, the reconstruction of the parcel-wise temporal spectral signature, and the crop classification process. The spatial and temporal features get adequately collaborated with land parcels received as basic analysis units. The comprehensive experiment of typical mountainous areas in Southwest China reveals the positive effect of introducing spatial distribution patterns on uncertainty reduction. It clarifies the significance of combining measures such as precise extraction of land parcels, prior knowledge constraints, feature recombination and expansion, classifier reinforcement, etc. to enhance crop identification in mountainous areas. In general, this study deepens the theoretical exploration of the remote sensing interpretation in crop mapping under complex terrain conditions and, in practice, provides a practical framework with higher accuracy and greater interpretability for the scenarios such as agricultural insurance and disaster assessment.

    DRformer: a progressive coupled multiscale CNN and condensed attention Transformer method for hyperspectral image super-resolution
    Qing CHENG, Boxuan WANG, Hongyan ZHANG
    2025, 54(7):  1230-1242.  doi:10.11947/j.AGCS.2025.20240485
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    The super-resolution technology of hyperspectral image aims to enhance the spatial detail and quality of low-resolution hyperspectral images for better applications in areas such as environmental monitoring. In recent years, machine learning techniques based on deep convolutional neural networks have made significant progress in single hyperspectral image super-resolution. However, challenges remain in balancing the learning of spatial multi-scale local features and global detail features. This paper presents a fusion network, DRformer, that integrates convolutional neural networks and Transformer architecture using a progressive sampling strategy. The network employs a multi-scale adaptive weighted spectral attention module for local feature extraction and selective emphasis of spectral information, followed by an initial upsampling. Subsequently, a CADR module based on the Transformer architecture is incorporated after a second upsampling to process global image features and enhance effective information. To verify the effectiveness and robustness of the network, experiments were conducted on the Chikusei and Houston2013 datasets. The results demonstrate that DRformer outperforms existing deep learning methods, including GDRRN, SSPSR, EUNet and MSDformer in terms of super-resolution performance. Additionally, ablation experiments were carried out to validate the effectiveness of each module in the network.

    High-precision extraction of building point cloud facade structure based on PCF-Net network
    Yufu ZANG, Shuye WANG, Zhen DONG, Chi CHEN, Ronggang HUANG
    2025, 54(7):  1243-1253.  doi:10.11947/j.AGCS.2025.20240225
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    As the application and promotion of digital twin cities and realistic three-dimensional construction progresses, urban high-precision modeling based on 3D point clouds has become one of the important tasks. Building fa?ade structures can serve as prior knowledge to assist in the rapid construction of high-accuracy 3D urban models. Therefore, exploring how to accurately extract building fa?ade structures from point cloud data is a research focus in detailed modeling. Currently, methods based on deep learning can use neural networks to understand complex building fa?ades, but the extraction accuracy for less common structures in fa?ades (such as doors, external air conditioning units) is still not high enough. To address this issue, this paper develops a novel deep learning neural network, position color fusion-net (PCF-Net), focusing on the extraction of small-sample structures in building fa?ades across three aspects: point cloud sampling, feature extraction, and loss function. Initially, during the point cloud sampling process, the proportion of small-sample structure point clouds is increased by attaching weights. Subsequently, a dual-branch network is used to extract spatial features from the colored point clouds and texture features, with an attention mechanism applied to adaptively fuse these two types of features, enhancing the description of key details in building fa?ades. Finally, a loss function that considers both intersection over union (IoU) and extraction accuracy (Acc) constraints is designed to improve the completeness and precision of building fa?ade structure extraction. Experiments show that the proposed PCF-Net network achieves precision metrics of 97.99% OA, 97.80% mAcc, and 95.75% mIoU in extracting fine structures from various types of building fa?ades, demonstrating the network's superior performance in building fa?ade structure extraction (Project address: https://github.com/zangyufus/PCF_net.git).

    Research on road extraction considering road boundaries and connectivity
    Yongyang XU, Jian WANG, Liang WU, Zhong XIE
    2025, 54(7):  1254-1264.  doi:10.11947/j.AGCS.2025.20240271
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    Road extraction is a crucial task in remote sensing image interpretation. This study addresses the issue of occlusion in road extraction tasks within remote sensing imagery by proposing a novel feature fusion network structure, KDLinkNet. The network incorporates a graph-based inference module, the road connectivity module (RCM), designed to enhance road connectivity and rectify missing details in complex scenes. Additionally, the study introduces an edge optimization (EO) method based on multi-task learning, which incorporates prior knowledge of road boundaries to improve the network's ability to extract boundary information. Experimental results demonstrate that this method achieves F1 scores of 94.0%, 79.8%, and 86.1% on the LRSNY, Massachusetts, and DeepGlobe datasets, respectively, outperforming current state-of-the-art methods. This research provides an effective solution for road extraction in complex remote sensing image scenarios.

    Edge and global features integrated network for salient object detection in optical remote sensing images
    Yakun XIE, Yaoji ZHAO, Jiaxing TU, Ruifeng XIA, Dejun FENG, Suning LIU, Hongyu CHEN, Jun ZHU
    2025, 54(7):  1265-1279.  doi:10.11947/j.AGCS.2025.20240247
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    Salient object detection in remote sensing images (SOD) effectively distinguishes key features and regions within images, thus enhancing the precision and efficiency of image analysis. However, due to the complexity of remote sensing images, existing remote sensing images SOD methods suffer from issues such as inaccurate target localization, blurred boundaries, and weak target confidence. To address these challenges, this paper proposes a novel method for remote sensing images SOD that integrates edge and global information. Initially, an edge feature enhancement module is designed, utilizing the Sobel operator to extract edge information from shallow feature maps to generate boundary clue feature maps. These are integrated with boundary attention and spatial-channel attention to further enhance local feature representation, effectively mitigating the issue of blurred salient object boundaries. Secondly, a global context feature enhancement module is introduced, acquiring image-level semantic information through global average pooling and fully connected layers, and combining it with spatial attention mechanisms to generate global association maps. Based on this, the multi-scale attention and context feature enhancement strategies are employed to improve the confidence and localization accuracy of salient objects. Finally, to validate the effectiveness of the proposed method, this paper conducted experimental analysis on three ORSSD datasets, the EORSSD dataset, and the ORSI4199 dataset. The scores decreased by 0.001 3~0.120 5, 0.001~0.159 3, and 0.003 5~0.136 7, respectively. The Sα scores increased by 0.005 7~0.266 3, 0.003~0.336 6, and 0.013 9~0.240 3, respectively. The Fβ scores increased by 0.031 4~0.339 1, 0.023 2~0.517 8, and 0.004 3~0.328 9, respectively. The results demonstrate that the proposed method significantly outperforms existing methods in detection accuracy and efficiency, effectively handling complex scenes and variable conditions in remote sensing images.

    A U-shaped graph convolution network method for semantic segmentation of vehicle LiDAR point clouds towards urban road scenes
    Jie WAN, Zhong XIE, Yongyang XU, Liufeng TAO
    2025, 54(7):  1280-1293.  doi:10.11947/j.AGCS.2025.20230481
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    Semantic segmentation of vehicle LiDAR point clouds aims to extract the 3D information of roads and various roadside objects, which is crucial for the objectification and 3D modeling of urban road scenes. Aiming at the challenges faced by current deep learning networks in handling vehicle LiDAR point clouds, including architectural constraints and difficulties in effectively extracting and utilizing multi-scale information, leading to inaccuracies in segmenting small objects, incomplete objects and occluded objects, this paper proposes a point cloud semantic segmentation method based on the U-shaped graph convolutional network (U-GCN). The proposed method firstly designed a dynamic graph convolutional operators that utilized learnable graph convolutional point kernels to adaptively extract local geometric features from the point cloud. Additionally, the cascaded dynamic graph convolutional operators were employed to construct a local feature aggregation module and expand the receptive field, enabling the capture of structural and contextual information on the objects. Subsequently, combined with the U-shaped encoder-decoder network architecture, deep and shallow point features are fused through skip connections to obtain multi-scale detailed information of objects, so as to enhance the feature representation of objects. Finally, a deep supervision loss function was introduced to guide the network to utilize output prediction information from different layers for the multiscale supervision training, further improving the network robustness and overall performance. Experiments on the Toronto-3D and WHU-MLS datasets show that the proposed method outperformed current mainstream networks in both visual analysis and quantitative evaluation. It can effectively improve the low segmentation accuracy caused by object scale variations, occlusion, and data incompleteness.

    Segmentation method of high-score remote sensing target based on road neighborhood relationship
    Chaoyang WANG, Yishao SU, Jiancheng LUO, Xiaodong HU, Liegang XIA
    2025, 54(7):  1294-1304.  doi:10.11947/j.AGCS.2025.20240276
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    In recent years, the advancement of deep learning technology has been a continuous process. The application of remote sensing image instance segmentation to a variety of datasets has yielded effective and efficient segmentation results. However, existing methods for the instances segmentation of remote sensing image usually only fuse spatial context information at the pixel level, while neglecting the mining of spatial relationships between feature targets. In this paper, we propose a research project on the high-resolution remote sensing target segmentation method fusing road neighborhood relations based on YOLOv8. This method introduces a coordinate attention module and a redesigned distance loss function, which focus on the spatial relations among feature targets and combine them with visual information to enhance the semantic understanding and pixel-level segmentation accuracy. This approach significantly improves the accuracy and efficiency of target segmentation.

    Cartography and Geoinformation
    A predictability measurement methodology for spatial panel data considering geo-spatial effects
    Min DENG, Chong PENG, Kaiqi CHEN
    2025, 54(7):  1305-1317.  doi:10.11947/j.AGCS.2025.20240448
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    Spatial panel data, characterized by the regularity of information in both spatial and temporal dimensions, are commonly used to record the spatial-temporal evolution of geographic phenomena, and are the mainstream data structure for spatial-temporal prediction research. Especially in the era of artificial intelligence centered on neural networks, spatial panel data can be input into intelligent models such as convolutional networks and recurrent networks without additional processing, which has the advantages of non-destructive information and convenient computation, and is commonly used in prediction research in the fields of human activities and transportation. However, the existing research focuses on the enhancement of modeling methods, and the theoretical issues of whether the data itself can be predicted, to what extent it can be predicted, and how it should be predicted are seldom addressed. There is entropy-based predictability theory in the field of information and statistics, which is widely used in time series analysis, but it neglects geo-spatial effects such as spatial dependence, spatial heterogeneity and geographic similarity in the spatial panel data and its influence mechanism on the prediction potential and modeling approach, which leads to inaccurate assessment results. In this regard, based on the existing predictability assessment theory, this paper proposes the geographic entropy theory and method, including neighborhood transfer entropy, cross-space entropy and cross-region entropy, taking into account the influence mechanism of geo-spatial effects, so as to quantitatively assess the predictability of spatial panel data from the different aspects of feature learning, parameter training, and application testing and to provide theoretical basis for the study of spatial-temporal prediction, spatial neighborhood learning, local model construction, and transfer and generalization strategy.

    Data and cognition dual-driven building group generalization results and scale consistency assessment
    Nina MENG, Fengmei LI, Xiaodong ZHOU
    2025, 54(7):  1318-1331.  doi:10.11947/j.AGCS.2025.20240490
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    The consistency between cartographic generalization results and their target scales constitutes a critical aspect of generalization quality evaluation. This process involves multidimensional factors including quantitative features, structural characteristics, and cognitive attributes. Traditional methods face difficulties in determining quantitative metrics when combining multiple evaluation indicators and encounter challenges in integrating domain knowledge such as spatial cognition. To address these limitations, this paper proposes a dilated graph convolutional network (DGCNN)-based recognition model for assessing scale consistency between building groups and their generalization results. The model adopts a dual data-driven and cognition-driven strategy to measure feature changes before and after generalization across three spatial-cognitive levels: global structure, local structure, and individual characteristics. It leverages multi-scale generalized datasets for training. Experimental results demonstrate that the proposed model effectively recognizes consistency between cartographic generalization outcomes and target scales.

    River network automated selection method based on heterogeneous graph convolutional networks
    Yaqing WANG, Zhonghui WANG
    2025, 54(7):  1332-1345.  doi:10.11947/j.AGCS.2025.20240337
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    River network selection is a map generalization process in which important rivers are selected and other rivers are discarded, due to space limitations when scaling down from large-scale to small-scale maps. Traditional deep learning methods typically focus on homogeneous graphs with a single type of relationship between river segments, which limits their ability to fully utilize the complex connectivity information between segments. This often results in lower selection accuracy and compromised topological connectivity. To address these issues, this paper introduces an automated river network selection method based on heterogeneous graph convolutional networks. In this method, river segments are represented as nodes, and their connections as edges. These edges are categorized into three types based on different relationship characteristics, creating a heterogeneous graph of the river network. The river network data and corresponding selection labels are input into the relational graph convolutional networks (RGCN) model, which aggregates information and classifies the nodes. River segments are selected based on the classification results, achieving automation in the selection process. Experiments using river network data at scales of 1∶24 000 and 1∶250 000 show that the proposed method significantly improves selection accuracy. Key performance metrics, including precision, recall, F1 score and AUC, all exceed 92%. Additionally, the method reduces river network discontinuities and better preserves the topological connectivity and shape similarity of the river network.

    Summary of PhD Thesis
    Automated settlement generalization methods considering geometric and semantic similarity
    Xiaorong GAO
    2025, 54(7):  1346-1346.  doi:10.11947/j.AGCS.2025.20230384
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