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    Cost based Load Balancing for Network Quality of GIS
    WANG Hao,PAN Shao-ming,YU Zhan-wu,LI Rui
    Acta Geodaetica et Cartographica Sinica   
    Acta Geodaetica et Cartographica Sinica   
    Abstract15270)      PDF(pc) (1846KB)(2270)       Save
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    The BeiDou coordinate system
    WEI Ziqing, WU Fumei, LIU Guangming
    Acta Geodaetica et Cartographica Sinica    2019, 48 (7): 805-809.   DOI: 10.11947/j.AGCS.2019.20190131
    Abstract6737)   HTML    PDF(pc) (826KB)(2391)       Save
    The BeiDou coordinate system(BDCS) is the geodetic datum of the BeiDou Satellite Navigation System. After a brief description of the backgrounds, the definition of origin, scale, and orientation, and the defining and deriving constants of the reference ellipsoid of the BDCS are given. Then addressed is the first realization of the BDCS, namely, the ITRF2014 coordinates at epoch 2010.0 and velocities of 8 monitoring stations of the BeiDou system, which has been achieved by processing four-phases GPS data for a global GNSS network including the monitoring stations, and by the frame alignment and the linear regression fitting of station coordinate series. Discussions and suggestions are made about the period of re-realization of the system, the monitoring stations' overseas layout and continuously observing, the generation and distribution of precise ephemerides of BeiDou satellites, and the standardization of the BDCS. Finally, a summary concludes the paper.
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    Research Progress and Methods of InSAR for Deformation Monitoring
    ZHU Jianjun, LI Zhiwei, HU Jun
    Acta Geodaetica et Cartographica Sinica    2017, 46 (10): 1717-1733.   DOI: 10.11947/j.AGCS.2017.20170350
    Abstract4653)   HTML    PDF(pc) (1654KB)(9069)       Save
    Deformation monitoring is one of the most mature applications of space-borne InSAR technique. Firstly, we introduce the basic principle of InSAR in the monitoring of deformation and the current SAR satellites. The deformation monitoring methods of InSAR are then classified into the groups of D-InSAR, PS-InSAR, SBAS-InSAR, DS-InSAR and MAI, which are analyzed in the aspects of technical features and application scopes. Subsequently, we analyze the research progress and deficiencies of InSAR in the investigation of urban, mining area, earthquake, volcano, infrastructure, glacier, permafrost and landslide. Finally, some advanced academic problems such as deformation monitoring in multi-demension and low coherence area, atmospheric and orbital errors mitigation, and accuracy assessment are concluded.
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    Photogrammetry and Deep Learning
    GONG Jianya, JI Shunping
    Acta Geodaetica et Cartographica Sinica    2018, 47 (6): 693-704.   DOI: 10.11947/j.AGCS.2018.20170640
    Abstract4622)   HTML    PDF(pc) (4176KB)(6551)       Save
    Deep learning has become popular and the mainstream in types of researches related to learning,and has shown its impact on photogrammetry.According to the definition of photogrammetry,a subject that researches shapes,locations,sizes,characteristics and inter-relationships of real objects from optical images,photogrammetry considers two aspects,geometry and semantics.From the two aspects,we review the history of deep learning and discuss its current applications on photogrammetry,and forecast the future development of photogrammetry.In geometry,the deep convolutional neural network (CNN) has been widely applied in stereo matching,SLAM and 3D reconstruction,and has made some effect but needs more improvement.In semantics,conventional empirical and handcrafted methods have failed to extract the semantic information accurately and failed to produce types of “semantic thematic map” as 4D productions (DEM,DOM,DLG,DRG) of photogrammetry,which causes the semantic part of photogrammetry be ignored for a long time.The powerful generalization capacity,ability to fit any functions and stability under types of situations of deep leaning is making the automated production of thematic maps possible.We review the achievements that have been obtained in road network extraction,building detection and crop classification,etc.,and forecast that producing high-accuracy semantic thematic maps directly from optical images will become reality and these maps will become a type of standard products of photogrammetry.At last,we introduce two current researches related to geometry and semantics respectively.One is stereo matching of aerial images based on deep learning and transfer learning; the other is fine crop classification from satellite special-temporal images based on 3D CNN.
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    Automatic Analysis and Mining of Remote Sensing Big Data
    LI Deren, ZHANG Liangpei, XIA Guisong
    Acta Geodaetica et Cartographica Sinica    2014, 43 (12): 1211-1216.   DOI: 10.13485/j.cnki.11-2089.2014.0187
    Abstract4554)   HTML    PDF(pc) (1314KB)(10937)       Save
    With the diversification of the imaging methods and the growing categories, quantity, and observation frequency of remote sensing data, the ability of land-cover observation has reached an unprecedented level, which means a new era of big data in remote sensing is coming. However, the existing methods and processing techniques cannot fulfill the need of the big data application in remote sensing. Thus, to develop the automatic analysis and mining theory and techniques for remote sensing big data is among the most advanced international research areas. This paper investigates and analyses the domestic and overseas research status and progress around this field and points out its key problems and developing trends.
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    New progress of PPP/PPP-RTK and positioning performance comparison of BDS/GNSS PPP
    ZHANG Xiaohong, HU Jiahuan, REN Xiaodong
    Acta Geodaetica et Cartographica Sinica    2020, 49 (9): 1084-1100.   DOI: 10.11947/j.AGCS.2020.20200328
    Abstract4264)   HTML234)    PDF(pc) (12168KB)(2855)       Save
    This paper begins with a brief review of the current state of development of precise point positioning (PPP) in recent years, with a focus on summarizing the latest research progress of several hotspots such as real-time rapid estimation of high-rate satellite clocks, multi-GNSS PPP ambiguity resolution, multi-frequency GNSS PPP models and ambiguity resolution, rapid initialization of PPP and PPP-RTK. Then, the evaluation of positioning performance of single/multi-GNSS PPP with latest observation of GPS, GLONASS, Galileo and BDS, especially the positioning accuracy, convergence time and time to first fix of BDS-2+3, is given. The results show that:PPP performance of BeiDou Navigation Satellite System is comparable with other GNSS. The convergence time and time to first fix of BDS-2 and BDS-3 combined PPP are about 20~30 minutes, positioning accuracy of static PPP in east, north and up directions is at millimeter to centimeter level, while that of kinematic PPP reach 5 cm in horizontal and 7 cm in elevation direction. Multi-GNSS combination can improve positioning accuracy and shorten the convergence time and time to first fix significantly, the positioning accuracy of ambiguity-fixed solutions can be improved by 14.8, 12.0 and 12.8% in the east, north and up directions compared to float solutions, respectively. The convergence time and time to first fix of multi-GNSS PPP can be reduced by 36.5 and 40.4% compared to that of GPS PPP.
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    Acta Geodaetica et Cartographica Sinica   
    Abstract4159)      PDF(pc) (1372KB)(3002)       Save
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    Progress, Challenges and Perspectives of 3D LiDAR Point Cloud Processing
    YANG Bisheng, LIANG Fuxun, HUANG Ronggang
    Acta Geodaetica et Cartographica Sinica    2017, 46 (10): 1509-1516.   DOI: 10.11947/j.AGCS.2017.20170351
    Abstract4085)   HTML    PDF(pc) (1579KB)(9383)       Save
    3D LiDAR can perform an intensive sampling of the earth surface in a direct way, and yield the 3D point cloud that contains numerous and scattered points with the coordinates ( X, Y, Z) and attributes (e.g., intensity). As the vital 3D geospatial data for description of the world in the digital era, 3D point cloud plays an important role not only in earth science researches but also in national requirements (e.g., global change analysis, global mapping, and smart city). Inspired by sensor technologies and national requirements, 3D LiDAR has got great progresses in hardware, data processing and applications, and is facing new challenges. Following the history of 3D LiDAR, this paper first reviews the status of 3D LiDAR system, and introduces the development of key technologies in data processing. Then the typical applications of 3D LiDAR in surveying and other related fields are listed, and current challenges in point cloud processing are concluded. Finally, some future perspectives are presented.
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    An Overview on Data Mining of Nighttime Light Remote Sensing
    LI Deren, LI Xi
    Acta Geodaetica et Cartographica Sinica    2015, 44 (6): 591-601.   DOI: 10.11947/j.AGCS.2015.20150149
    Abstract3594)   HTML    PDF(pc) (1051KB)(6367)       Save

    When observing the Earth from above at night, it is clear that the human settlement and major economic regions emit glorious light. At cloud-free nights, some remote sensing satellites can record visible radiance source, including city light, fishing boat light and fire, and these nighttime cloud-free images are remotely sensed nighttime light images. Different from daytime remote sensing, nighttime light remote sensing provides a unique perspective on human social activities, thus it has been widely used for spatial data mining of socioeconomic domains. Historically, researches on nighttime light remote sensing mostly focus on urban land cover and urban expansion mapping using DMSP/OLS imagery, but the nighttime light images are not the unique remote sensing source to do these works. Through decades of development of nighttime light product, the nighttime light remote sensing application has been extended to numerous interesting and scientific study domains such as econometrics, poverty estimation, light pollution, fishery and armed conflict. Among the application cases, it is surprising to see the Gross Domestic Production (GDP) data can be corrected using the nighttime light data, and it is interesting to see mechanism of several diseases can be revealed by nighttime light images, while nighttime light are the unique remote sensing source to do the above works. As the nighttime light remote sensing has numerous applications, it is important to summarize the application of nighttime light remote sensing and its data mining fields. This paper introduced major satellite platform and sensors for observing nighttime light at first. Consequently, the paper summarized the progress of nighttime light remote sensing data mining in socioeconomic parameter estimation, urbanization monitoring, important event evaluation, environmental and healthy effects, fishery dynamic mapping, epidemiological research and natural gas flaring monitoring. Finally, future trends of nighttime light remote sensing and its data mining have been proposed from four aspects including new data source, knowledge discovery, in-situ observation, and national/global geographic conditions monitoring.

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    Micro-PNT and Comprehensive PNT
    YANG Yuanxi, LI Xiaoyan
    Acta Geodaetica et Cartographica Sinica    2017, 46 (10): 1249-1254.   DOI: 10.11947/j.AGCS.2017.20170249
    Abstract3431)   HTML    PDF(pc) (1445KB)(2966)       Save
    Comprehensive or integrated positioning, navigation and timing is an obvious developing trend following the global navigation satellite system.This paper summarizes the current status of micro-PNT and its developing requirements. The related key technologies are described and the relationship between comprehensive PNT and micro-PNT is analyzed. It is stressed that the comprehensive PNT needs massive infrastructure construction and investment, however, the micro-PNT aims at the integrated applications of high-tech micro sensors. It is different from the current opinions appeared in the literatures, micro-PNT should include multi GNSS integration and micro components of navigation and timing in order to make the PNT outputs refer to a unified coordinate datum and time scale. Micro-PNT focuses on the personalized micro terminal applications. Except for the miniaturization of each PNT component, micro-PNT aims at the deep integration of the micro sensors, adaptive data fusion and self calibration of each component.
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    Parameters of the CGCS2000 ellipsoid and comparisons with GRS80 and WGS84
    Acta Geodaetica et Cartographica Sinica   
    Review of GNSS PPP and Its Application
    ZHANG Xiaohong, LI Xingxing, LI Pan
    Acta Geodaetica et Cartographica Sinica    2017, 46 (10): 1399-1407.   DOI: 10.11947/j.AGCS.2017.20170327
    Abstract3360)   HTML    PDF(pc) (1456KB)(6382)       Save
    In this paper, we summarized the development of precise point positioning (PPP)technologies and its applications. Key technologies and methodologies for PPP float solution, ambiguity-fixing PPP, real-time PPP and multi-GNSS PPP were intensively analyzed and discussed. Typical PPP applications were summarized and demonstrated. Finally, we illustrated the prospect of PPP and pointed out problems to be solved for PPP development and applications in the coming years.
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    An Adaptive Density-Based Spatial Clustering Method
    LI Guang-Qiang , , ,
    Acta Geodaetica et Cartographica Sinica   
    TH-2 satellite engineering design and implementation
    LOU Liangsheng, LIU Zhiming, ZHANG Hao, QIAN Fangming, HUANG Yan
    Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1252-1264.   DOI: 10.11947/j.AGCS.2020.20200175
    Abstract3236)   HTML125)    PDF(pc) (5520KB)(1984)       Save
    The TH-2 satellite system is China's first microwave surveying satellite system based on interferometric synthetic aperture radar technology, and is also China's first short-range formation satellite system. It is the second microwave interferometric surveying satellite system after the German's TanDEM-X system in the world. A method to solve the problem of absolute ambiguity in the interference phase by designing dual-frequency imaging is proposed for the first time in the world, which completely got rid of the dependence on ground control data. The system works in the X band, with the resolution of 3 m and a solar synchronous orbit of 500 km. It is composed of two equal satellites. It adopts a technical system of satellite formation in different orbits and a bistatic radar transceiver mode. It can measure the global digital surface models and acquire radar orthophotos in a short time. In this paper, through the selection of the interference baseline system, satellite formation configuration and radar transceiver mode, the technical system of TH-2 satellite is proposed. The engineering design is carried out from three aspects:system mission, main performance and composition. The implementation of the project is expounded from the three stages of the overall demonstration, the key technical research and verification, and project development. Finally, the on-orbit test and verification of the satellite system is introduced. Test results show that all indicators have reached the requirements of engineering design, products' precision is equivalent to TanDEM -X system and can meet the 1:50 000 scale mapping accuracy. These verify the TH-2 satellite' engineering design ideas correct and the method of project implementation reasonable and feasible.
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    Deep learning algorithm for feature matching of cross modality remote sensing images
    LAN Chaozhen, LU Wanjie, YU Junming, XU Qing
    Acta Geodaetica et Cartographica Sinica    2021, 50 (2): 189-202.   DOI: 10.11947/j.AGCS.2021.20200048
    Abstract3176)   HTML232)    PDF(pc) (25649KB)(3183)       Save
    Focusing on the problem of difficulty in matching due to the differences in imaging modality, time phases, and resolutions of cross modality remote sensing images, a new deep learning feature matching method named CMM-Net is proposed. First, a convolutional neural network is used to extract high-dimensional feature maps of the cross modality remote sensing images. The key points are selected according to the conditions that both the channel maximum and local maximum are met, and the 512-dimensional descriptors in corresponding location are extracted on the feature map to complete the feature extraction. In the matching stage, after completing the fast-nearest neighbor searching, in order to solve the problem of lots of mismatched points, a purification algorithm with dynamic adaptive Euclidean distance and RANSAC constraints is proposed to ensure that the mismatches are effectively eliminated while retaining the correct matches. The algorithm was tested using multiple sets of cross modality remote sensing images and compared with other algorithms. The results show that the proposed algorithm has the ability to extract similar scale invariant features in cross modality images, and has strong adaptability and robustness.
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    Automatic Placement of Annotation in Area Feature:
    A Metric Information Approach
    WANG Zhao,WU Zhong-heng, LI Li-xia
    Acta Geodaetica et Cartographica Sinica   
    Concepts of Comprehensive PNT and Related Key Technologies
    YANG Yuanxi
    Acta Geodaetica et Cartographica Sinica    2016, 45 (5): 505-510.   DOI: 10.11947/j.AGCS.2016.20160127
    Abstract3089)   HTML    PDF(pc) (1232KB)(3440)       Save
    The core idea of comprehensive positioning, navigation and time (PNT) is the technique that uses all the available resources to provide PNT services in the whole area, including inside and outside door, air, space, under water and underground, which does not solely rely on the GNSS. The definition and basic concepts of the comprehensive PNT are presented. The possible signal sources are listed. The core technologies related to the comprehensive PNT are analyzed, including the integration of the multiple sensors and adaptive data fusion for multiple PNT signals. It is emphasized that the information of the comprehensive PNT should be from "multiple sources based on different physical principles", the control system should be operated by voluntary users based on cloud platform, the user terminals or sensors should be "deeply integrated" and the PNT information should be "adaptively fused" and serve mode might be based on cloud platform. The comprehensive PNT system should meet the robust availability, continuity, high accuracy and reliability with unified geodetic datum and time datum.
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