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An optimal design of the broadcast ephemeris for LEO navigation augmentation systems

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Geo-Spatial Information Science 2022年第1期25卷 34-46页

作者： Xueli Guo Lei Wang Wenju Fu Yingbo Suo Ruizhi Chen Hongxing Sun state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan UniversityWuhanChina Collaborative Innovation Center for Geospatial Technology WuhanChina

As the deployment of large Low Earth Orbiters(LEO)communication constellations,navigation from the LEO satellites becomes an emerging opportunity to enhance the existing satellite navigation *** LEO navigation augmentation(LEO-NA)systems require a centimeter to decimeter accuracy broadcast ephemeris to support high accuracy positioning ***,how to design the broadcast ephemeris becomes the key issue for the LEO-NA *** this paper,the temporal variation characteristics of the LEO orbit elements were analyzed via a spectrum analysis.A non-singular element set for orbit fitting was introduced to overcome the potential singularity problem of the LEO *** on the orbit characteristics,a few new parameters were introduced into the classical 16 parameter ephemeris set to improve the LEO orbit fitting *** order to identify the optimal parameter set,different parameter sets were tested and compared and the 21 parameters data set was recommended to make an optimal balance between the orbit accuracy and the bandwidth *** the real-time broadcast ephemeris generation procedure,the performance of the LEO ephemeris based on the predicted orbit is also *** performance of the proposed ephemeris set was evaluated with four in-orbit LEO satellites and the results indicate the proposed 21 parameter schemes improve the fitting accuracy by 87.4%subject to the 16 parameters *** accuracy for the predicted LEO ephemeris is strongly dependent on the orbit *** these LEO satellites operating higher than 500 km,10 cm signal-in-space ranging error(SISRE)is achievable for over 20 min prediction.

关键词： LEO broadcast ephemeris orbit fitting leo navigation augmentation orbit prediction

Geoinformatics education in China

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Geo-Spatial Information Science 2014年第4期17卷 208-218页

作者： Deren LI Jianya GONG Peng YUE state key laboratory of Information Engineering in surveying Mapping and Remote Sensing(LIESMARS)Wuhan UniversityWuhan 430079China

The paper gives an overview of the current status of education in geoinformatics in ***,the paper provides a brief introduction to the history of geoinformatics education in China and a general review of the scientific and technological *** then presents how the development affects the education and training in *** the paper,universities and institutes in China that can award academic degrees related to geoinformatics are summarized,and undergraduate majors are briefly ***,the paper reports the work having been done by the national expert group on surveying and Mapping,including the revision of discipline catalog and guide for graduate education and requirements.A list of typical curricula in geoinformatics education is *** on promoting the graduate student exchange platform are ***,a case study of geoinformatics education in Wuhan University is discussed.

关键词： geoinformatics surveying and Mapping remote sensing science and technology geographical information science(GIS) education and training China

Detecting building changes with off-nadir aerial images

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Science China(Information Sciences) 2023年第4期66卷 107-121页

作者： Chao PANG Jiang WU Jian DING Can SONG Gui-Song XIA School of Computer Science Wuhan University Sense Time Research state key laboratory of Information Engineering in surveying Mapping and Remote Sensing(LIESMARS) Wuhan University

The tilted viewing nature of the off-nadir aerial images brings severe challenges to the building change detection(BCD) problem: the mismatch of the nearby buildings and the semantic ambiguity of the building facades. To tackle these challenges, we present a multi-task guided change detection network model,named as MTGCD-Net. The proposed model approaches the specific BCD problem by designing three auxiliary tasks, including:(1) a pixel-wise classification task to predict the roofs and facades of buildings;(2) an auxiliary task for learning the roof-to-footprint offsets of each building to account for the misalignment between building roof instances; and(3) an auxiliary task for learning the identical roof matching flow between bi-temporal aerial images to tackle the building roof mismatch problem. These auxiliary tasks provide indispensable and complementary building parsing and matching information. The predictions of the auxiliary tasks are finally fused to the main BCD branch with a multi-modal distillation module. To train and test models for the BCD problem with off-nadir aerial images, we create a new benchmark dataset,named BANDON. Extensive experiments demonstrate that our model achieves superior performance over the previous state-of-the-art competitors.

关键词： change detection high-resolution imagery multi-task learning off-nadir imagery remote sensing dataset

An internal-external optimized convolutional neural network for arbitrary orientated object detection from optical remote sensing images

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Geo-Spatial Information Science 2021年第4期24卷 654-665页

作者： Sihang Zhang Zhenfeng Shao Xiao Huang Linze Bai Jiaming Wang state key laboratory of Information Engineering in surveying Mapping and Remote Sensing Wuhan UniversityWuhanChina Department of Geosciences University of ArkansasFayettevilleNCUSA

Due to the bird’s eye view of remote sensing sensors,the orientational information of an object is a key factor that has to be considered in object *** obtain rotating bounding boxes,existing studies either rely on rotated anchoring schemes or adding complex rotating ROI transfer layers,leading to increased computational demand and reduced detection *** this study,we propose a novel internal-external optimized convolutional neural network for arbitrary orientated object detection in optical remote sensing *** the internal opti-mization,we designed an anchor-based single-shot head detector that adopts the concept of coarse-to-fine detection for two-stage object detection *** refined rotating anchors are generated from the coarse detection head module and fed into the refining detection head module with a link of an embedded deformable convolutional *** the external optimiza-tion,we propose an IOU balanced loss that addresses the regression challenges related to arbitrary orientated bounding *** results on the DOTA and HRSC2016 bench-mark datasets show that our proposed method outperforms selected methods.

关键词： Arbitrary orientated object detection optical remote sensing image single-shot deep learning

Detection of the Inner Core Translational Triplet Using Superconducting Gravimetric Observations

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Journal of Earth Science 2013年第5期24卷 725-735页

作者：申文斌丁浩 Department of Geophysics School of Geodesy and Geomatics Wuhan University state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan University

Based upon seven superconducting gravimeter （SG） records of 20 000 h length after the 2004 Sumatra earthquake, four methods, namely the ensemble empirical mode decomposition （EEMD）, the multi-station experiment （MSE） technique, the autoregressive （AR） method and the product spec- trum analysis （PSA） method, are chosen jointly together to detect the inner core translational modes （1S1）. After the conventional pretreatment, each of the seven simultaneous residual gravity series is di- vided into five segments with an 80% overlap, and then EEMD is applied to all the 35 residual SG se- ries as a dyadic filter bank to get 35 filtered series. After then, according to different stations and dif- ferent time windows, five new simultaneous gravity datasets are obtained. After using MSE for each of the five new datasets, the AR method is used to demodulate some known harmonic signals from the new sequences that obtained by using MSE, and three demodulated product spectra are obtained. Then, according to two criterions, two clear spectral peaks at periods of 4.548 9±2.3×10^-5 and 3.802 3±3.2×10^-5 h corresponding respectively to the singlets m=-1 and m=＋l are identified from various spectral peaks, and they are close to the predictions of the 1066A model given by Rieutord （2002）, but no spectral peak corresponding to the singlet m=0 is found. We conclude that the selected two peaks might be the ob- served singlets of the Slichter triplet.

关键词： Slichter triplet superconductinggravimeter EEMD multi-station experimenttechnique product spectrum analysis.

Taiyuan City Subsidence Observed with Persistent Scatterer InSAR

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Wuhan University Journal of Natural Sciences 2014年第6期19卷 526-534页

作者： TANG Wei LIAO Mingsheng state key laboratory of Information Engineering in surveying Mapping and Remote Sensing Wuhan University

C- and X-bands Synthetic Aperture Radar（SAR） images acquired from February 2009 to September 2010 were processed with Persistent Scatterer Interferometry（PS-InSAR） algorithm to investigate spatial and temporal variations in deformation over Taiyuan City, China. The spatial pattern of subsidence and the magnitude of subsidence rate are similar in the velocity field maps achieved by the algorithm from these two data sets. It shows that there are four primary subsidence centers in Taiyuan City：Xiayuan, Wujiabao, Xiaodian, Sunjiazhai, which are near the groundwater extraction wells. The maximum subsidence rate is up to 70 mm/year at Sunjiazhai. The locus of maximum subsidence has shifted from its historical location in the north to the south. In view of the severe shortage of water resources and presented features of subsidence over Taiyuan City, we inferred that excessive pumping of groundwater was the dominant reason of land subsidence.

关键词： ground subsidence Synthetic Aperture Radar interferometry persistent scatterer

Geometric positioning integrating optical satellite stereo imagery and a global database of ICESat-2 laser control points:A framework and key technologies

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Geo-Spatial Information Science 2023年第2期26卷 206-217页

作者： Mi Wang Yu Wei Yingdong Pi state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan UniversityWuhanChina School of Resource and Environmental Sciences Wuhan UniversityWuhanChina

Block Adjustment(BA)is one of the essential techniques for producing high-precision geospatial 3D data products with optical stereo satellite *** block adjustment with few ground-control points or without ground control,the vertical error of the model is the decisive factor that constrains the accuracy of 3D data *** elevation data obtained by spaceborne laser altimeter have the advantages of short update periods,high positioning precision,and low acquisition cost,providing sufficient data support for improving the elevation accuracy of stereo models through the combined *** paper proposes a geometric positioning model based on the integration of Optical Satellite Stereo Imagery(OSSI)and spaceborne laser altimeter ***,we elaborate the principle and necessity of this work through a literature review of existing ***,the framework of our geo-positioning ***,four key technologies of the proposed model are expounded in order,including the acquisition and management of global Laser Control Points,the association of LCPs and OSSI,the block adjustment model combining LCPs with OSSI,and the accuracy estimation and quality control of the combined ***,the combined BA experiment using Ziyuan-3(ZY-3)OSSI and ICESat-2 laser data was carried out at the testing site in Shandong Province,*** results prove that our method can automatically select LCPs with high *** elevation deviation of the combined BA eventually achieved the Mean Error(ME)of 0.06 m and the Root Mean Square Error(RMSE)of 1.18 m,much lower than the ME of 13.20 m and the RMSE of 3.88 m before the block adjustment.A further research direction will be how to perform more adequate accuracy analysis and quality control using massive laser points as checkpoints.

关键词： Spaceborne laser altimeter ICESat-2 optical stereo imagery ZY-3 combined block adjustment block adjustment without ground control geometric positioning stereo mapping

Lidar observation campaigns on diurnal variations of the sodium layer in Beijing and Wuhan, China

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Science China Earth Sciences 2015年第8期58卷 1377-1386页

作者： GONG ShaoHua YANG GuoTao CHENG XueWu GONG Shun Sheng XU JiYao LI FaQuan GONG Wei WANG JiHong School of Physics and Electronics Engineering Hainan Normal University state key laboratory of Space Weather National Space Science Center Chinese Academy of Sciences laboratory of Optoelectronics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences state key laboratory of Information Engineering in surveying Mapping and Remote Sensing Wuhan University

Based on observations from daytime lidars in eastern China,diurnal cycles of the sodium layer over Wuhan(30.5°N,114.6°E)and Beijing(40.5°N,116°E)are *** variations of Na density,root mean square(RMS)layer width,and centroid height of the sodium layer are *** reveal that the large diurnal cycles of the sodium layer are controlled mainly by 24-hr oscillations at the two observation *** diurnal variation of the sodium layer over Wuhan was modulated mainly by tidal perturbations during the lidar observation ***,the diurnal variation over Beijing was controlled principally by photoionization and photochemistry effects during another campaign,and there was little evidence of direct tidal *** comparisons suggest that the diurnal variation of the sodium layer perhaps has obvious regional characteristics across *** variation can be either controlled mainly by tidal perturbations or by photoionization and photochemistry effects in different seasons.

关键词： daytime lidar diurnal variations of the sodium layer photochemistry effects tidal perturbations

Design and Implementation of 3D Model Database for General-Purpose 3D GIS

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Geo-Spatial Information Science 2010年第3期13卷 210-215页

作者： XU Weiping ZHU Qing DU Zhiqiang ZHANG Yeting state key laboratory of Information Engineering in surveying Mapping and Remote Sensing Wuhan University129 LuoyuRoad Wuhan 430079 China

To improve the reusability of three-dimensional （3D） models and simplify the complexity of natural scene reconstruction, this paper presents a 3D model database for universal 3D GIS. After the introduction of its extensible function architecture, accompanied by the conclusion of implicit spatial-temporal hierarchy of models in any reconstructed scene of 3D GIS for general purpose, several key issues are discussed in detail, such as the storage and management of 3D models and related retrieval and load method, as well as the interfaces for further on-demand development. Finally, the validity and feasibility of this model database are proved through its application in the development of 3D visualization system of railway operation.

关键词： 3D model database 3D GIS 3D modeling CAD models