Table of Content

20 October 2016, Volume 45 Issue 10

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Preliminary Location Accuracy Assessments of 3rd Satellite of TH-1

WANG Renxiang, WANG Jianrong, HU Xin

2016, 45(10):  1135-1139.  doi:10.11947/j.AGCS.2016.20160373

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The TH-1 satellite is the first stereo mapping transmission satellite in China, and the primary mission goal of the satellite is for topographic mapping at 1:50 000 scale and high-accuracy location without Ground Control Points (GCPs). 1^st, 2^nd satellites of TH-1 were launched on August 24, 2010, May 6, 2012, and 3^rd satellite was launched on October 26, 2015. Now, three satellites of TH-1 are well operating on its orbit. After evaluation, the location accuracy of 1^st satellite without GCPs is 10.3 m/5.7 m (horizontal accuracy/vertical elevation accuracy), and the location accuracy of 2^nd is equivalent with 1^st satellite. In this paper, the system overview of TH-1 and the key technical in ground image processing are introduced. Then, the preliminary location accuracy of 3^rd is assessed. The results are shown using three routes images:the location accuracy of 3^rd is higher than 2^nd, and can realize high accuracy location without GCPs, in which the horizontal accuracy is 7.2 m, and the vertical elevation accuracy is 2.6 m.

Non-equidistant Multi-point Deformation Prediction Model and Its Application

YIN Hui, ZHOU Xiaoqing, ZHANG Xiaoming

2016, 45(10):  1140-1147.  doi:10.11947/j.AGCS.2016.20160005

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Taking consideration of the integrity modeling with correlative multiple deformation points, this paper extends the single point deformation analysis into spatial multi-point integrity analysis and presents a non-equidistant multi-point modeling by improving equispacing processing for the non-equidistant series. The real practical analysis and comparative results indicate that the non-equidistant multi-point prediction model is feasible and effective, which is a new nonlinear approach to the integrated deformation analysis and prediction in time and space domain.

A Water Storage Loading Model by SRTM-DEM Data and Surface Response Simulation of Gravity and Deformation in the Three Gorges Reservoir of China

WANG Linsong, CHEN Chao, MA Xian, DU Jinsong

2016, 45(10):  1148-1156.  doi:10.11947/j.AGCS.2016.20160016

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This paper aims to study relationships between water loading and its surface responses of gravity and crustal deformation over the Three Gorges Reservoir (TGR) according to time-varying water level data. Based on congruent relationship between high resolution SRTM-DEM data and topography of spatial boundaries of main channel and tributaries, we built a new water storage loading model under different water level in the TGR. Besides, mathematical expressions between water areas, volumes and water level data were fitted by power law relationships. Using new constructed water storage loading model, the elastic load response equation and mascon fitting method, we modelled the ground spatial distribution of the gravity and displacement fields when water level impoundment on the second and the third stages of the TGR. Meanwhile, time-varying water storage capacity model was obtained by Stokes spherical harmonic analysis (degree and order up to 60), and our results are analyzed with monitoring results from the GRACE data. GRACE-derived Terrestrial Water Storage (TWS) after using output from the CLM4.5 hydrology model shows very good agreement with the TGR prediction, but the difference between GRACE-derived and mascon fitting results may contain the groundwater seepage effect under huge water load pressure.The modelling results of this study will provide important basis of comparative analysis and related corrections to observations, and therefore, will be helpful to reveal masked relationships between the activities of landslips and reservoir induced earthquakes with the variation of reservoir's water loading.

Solution Method and Precision Analysis of Multi-days Orbit Combination of BeiDou Satellites

LIU Weiping, HAO Jinming, YU Heli, TIAN Yingguo

2016, 45(10):  1157-1164.  doi:10.11947/j.AGCS.2016.20160055

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Multi-days orbit of BeiDou satellites is gotten by the routine method of stacking observation data at present, which limits calculation efficiency. And moreover, the dynamic model of BeiDou satellites is not perfect because of the short running time, which also limits the precision of multi-days orbit. The method of multi-days BeiDou satellite orbit combination is present. In this method, normal equation stacking is used to combining some consecutive one-day BeiDou satellite orbits to one multi-days orbit, which can improve calculation efficiency. Meanwhile, pseudo-stochastic pulse is used to compensate the deficiency of dynamic model. The analysis shows that it is the pseudo-stochastic pulse at one-day boundary that improves the precision of BeiDou satellite orbits obviously. And the tangential and normal precision is improved more than the radial. The orbit precision of GEO and IGSO is improved more than that of MEO. And the precision of BeiDou satellite orbit can be improved by extending the orbit arc length with certain limits, which is especially in the tangential direction.

The Impact of Yaw Attitude of Eclipsing GPS/BDS Satellites on Phase Wind-up Solutions for PPP and Its Correction Model

FAN Caoming, WANG Shengli, OU Jikun

2016, 45(10):  1165-1170.  doi:10.11947/j.AGCS.2016.20160126

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Care of the phase wind-up correction should be reasonably taken in precise point positioning. In practice, correct computation of phase wind-up relies mainly upon the information about the satellite attitude, which should be modeled differently when satellites undergo eclipsing. Different GPS satellite types would be subject to different eclipsing periods. For instance, GPS ⅡR satellites can experience noon and midnight turn maneuvers, GPS ⅡF satellites suffer from noon maneuver and shadow crossing, and GPS Ⅱ/ⅡA satellites may further experience post-shadow recovery periods when compared to ⅡF ones. As for the BDS non-GEO satellites, one should take into account the attitude control switching between the nominal and the orbit-normal mode. This paper presents a model enabling the attitude to be correctly computed for both eclipsing as well as non-eclipsing satellites. Numerical tests using real data are then performed in order to verify our model presented. As far as the filtered residuals are concerned, it is found that, their maximum residual could exceed 20 cm during the eclipsing periods. This problem is fortunately solvable when use of our model has been made, since the residuals reduce to below 5 cm. It should be noted that, our numerical results may be slightly different when we use precise satellite orbit and clock products delivered by different Analysis Centers. Furthermore, the shadow crossing period takes typically up to 1 hour for GPS Ⅱ/ⅡA satellites, during which the yaw attitude is controlled entirely by the positive yaw bias (Ⅱ/ⅡA of0.5°). The Ⅱ/ⅡA post-shadow recovery periods, covering about 30 minutes, still cannot be fully modeled; the data collected within this period should thereby be excluded.

A Multi-view Dense Matching Algorithm of High Resolution Aerial Images Based on Graph Network

YAN Li, FEI Liang, CHEN Changhai, YE Zhiyun, ZHU Ruixi

2016, 45(10):  1171-1181.  doi:10.11947/j.AGCS.2016.20160068

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A multi-view dense matching algorithm of high resolution aerial images based on graph network was presented. Overlap ratio and direction between adjacent images was used to find the candidate stereo pairs and build the graph network, then a Coarse-to-Fine strategy based on modified semi-global matching algorithm (SGM) was adapted to calculate the disparity map of stereo pairs. Finally, dense point cloud was generated and fused using a multi-triangulation method based on graph network. In the experiment part, the Vaihingen aerial image dataset and the oblique nadir image block of Zürich in ISPRS/EuroSDR project were used to test the algorithm above. Experiment results show that out method is effective for multi-view dense matching of high resolution aerial images in consideration of completeness, efficiency and precision, while the RMS of average reprojection error can reach subpixel level and the actual deviation is better than 1.5 GSD. Due to the introduction of guided median filter, regions of sharp discontinuities, weak textureness or repeat textureness like buildings, vegetation and water body can also be matched well.

The Rigorous Geometric Model of Satellite Laser Altimeter and Preliminarily Accuracy Validation

TANG Xinming, LI Guoyuan, GAO Xiaoming, CHEN Jiyi

2016, 45(10):  1182-1191.  doi:10.11947/j.AGCS.2016.20150357

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It has been paid attention to improving the elevation accuracy of satellite stereo images aided by laser altimeter. The GF-7 satellite scheduled to launch in 2018 will be equipped with optical stereo cameras and a laser altimeter. ICESat (Ice, Cloud, and land Elevation Satellite) with GLAS(Geo-science Laser Altimeter System) is the first and still only laser altimeter satellite for earth observation until now. In this paper, the comprehensively analysis about the rigorous geometric model and accuracy analysis of laser altimeter is presented. The error induced by laser pointing aberration and mounting is proposed, and the data processing workflow of ICESat/GLAS from level 0 to level 2 is introduced. What's more, the geo-location accuracy between this paper and GLAS product is compared and the model is validated by the result that the accuracy based on the model is about 3 cm and 11 cm in the horizontal and vertical direction, respectively. The laser altimeter data loaded on the ZY3-02 satellite has been processed and validated preliminarily. The conclusion of this paper is valuable and can be viewed as reference for the subsequent domestic laser altimeter satellites.

A Fast Multi-layer Subnetwork Connection Method for Time Series InSAR Technique

WU Hong'an, ZHANG Yonghong, KANG Yonghui, GUO Ming

2016, 45(10):  1192-1199.  doi:10.11947/j.AGCS.2016.20160033

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Nowadays, times series interferometric synthetic aperture radar (InSAR) technique has been widely used in ground deformation monitoring, especially in urban areas where lots of stable point targets can be detected. However, in standard time series InSAR technique, affected by atmospheric correlation distance and the threshold of linear model coherence, the Delaunay triangulation for connecting point targets can be easily separated into many discontinuous subnetworks. Thus it is difficult to retrieve ground deformation in non-urban areas. In order to monitor ground deformation in large areas efficiently, a novel multi-layer subnetwork connection (MLSC) method is proposed for connecting all subnetworks. The advantage of the method is that it can quickly reduce the number of subnetworks with valid edges layer-by-layer. This method is compared with the existing complex network connecting mehod. The experimental results demonstrate that the data processing time of the proposed method is only 32.56% of the latter one.

Improved Adaptive Goldstein Interferogram Filter Based on Second Kind Statistics

ZHAO Wensheng, JIANG Mi, HE Xiufeng

2016, 45(10):  1200-1209.  doi:10.11947/j.AGCS.2016.20150457

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Interferometric filtering is one of the most important procedures in InSAR data processing as it refers to the quality of phase observations and the final products. A variant under the framework of Goldstein filter is presented in this paper, which is based on the robust coherence estimator from the second kind statistics. Compared with the state-of-the-art, the significant advantage of the new method is that more accurate filtering parameter alpha can be deduced and therefore better performance of the Goldstein filtering can be expected. Experimental results from both simulation and real Envisat ASAR data demonstrate the value of the method.

Snow Cover Recognition for Qinghai-Tibetan Plateau Using Deep Learning and Multispectral Remote Sensing

KAN Xi, ZHANG Yonghong, CAO Ting, WANG Jiangeng, TIAN Wei

2016, 45(10):  1210-1221.  doi:10.11947/j.AGCS.2016.20160183

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Snow cover in Qinghai-Tibetan plateau (QT plateau) is very important to global climate change. Because of the complex topography and high altitude, the recognition accuracies of existing snow cover products in QT plateau are significantly lower than flat areas. This paper proposed a new method of snow cover recognition for QT plateau based on deep learning. The multispectral remote sensing data from Chinese meteorological satellite FY-3A and the multiple geographic elements information are put together as the data sources, the insitu snow depth measurements and existing snow cover products are used for selecting the labeled samples. A stacked denoising auto-encoders (SDAE) network was built and trained for feature extraction and classification, this network can be used as a classifier for distinguishing the snow cover from cloud and other snow-free surface features. The recognition results are verified by snow depth data of meteorological station observations, verification results show that the recognition accuracy of this method is significantly higher than the snow product FY-3A/MULSS, which is using the same remote sensing data source FY-3A, and slightly higher than the widely used snow products MOD10A1 and MYD10A1,and the cloud coverage rate of this method is the lowest. According to the validation results, this method can effectively improve the accuracy of snow cover recognition, and reduce the interference of clouds.

An Anomaly Detector Based on Multi-aperture Mapping for Hyperspectral Data

LI Min, ZHU Guokang, ZHANG Xuewu, FAN Xinnan, LI Puhuang

2016, 45(10):  1222-1230.  doi:10.11947/j.AGCS.2016.20160119

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Considering the correlationship of spectral content between anomaly and clutter background, inaccurate selection of background pixels induced estimation error of background model. In order to solve the above problems, a multi-aperture mapping based anomaly detector was proposed in this paper. Firstly, differing from background model which focused on feature extraction of background, multi-aperture mapping of hyperspectral data characterized the feature of whole hyperspectral data. According to constructed basis set of multi-aperture mapping, anomaly salience index of every test pixel was proposed to measure the relative statistic difference. Secondly, in order to analysis the moderate salience anomaly precisely, membership value was constructed to identify anomaly salience of test pixels continuously based on fuzzy logical theory. At same time, weighted iterative estimation of multi-aperture mapping was expected to converge adaptively with membership value as weight. Thirdly, classical defuzzification was proposed to fuse different detection results. Hyperspectral data was used in the experiments, and the robustness and sensitivity to anomaly with lower silence of proposed detector were tested.

Fusion of Pixel-based and Object-based Features for Road Centerline Extraction from High-resolution Satellite Imagery

CAO Yungang, WANG Zhipan, SHEN Li, XIAO Xue, YANG Lei

2016, 45(10):  1231-1240.  doi:10.11947/j.AGCS.2016.20160158

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A novel approach for road centerline extraction from high spatial resolution satellite imagery is proposed by fusing both pixel-based and object-based features. Firstly, texture and shape features are extracted at the pixel level, and spectral features are extracted at the object level based on multi-scale image segmentation maps. Then, extracted multiple features are utilized in the fusion framework of Dempster-Shafer evidence theory to roughly identify the road network regions. Finally, an automatic noise removing algorithm combined with the tensor voting strategy is presented to accurately extract the road centerline. Experimental results using high-resolution satellite imageries with different scenes and spatial resolutions showed that the proposed approach compared favorably with the traditional methods, particularly in the aspect of eliminating the salt noise and conglutination phenomenon.

A Rapid Adaptive Reconstruction Method for Stereoscopic Images

DONG Yang, FAN Dazhao, JI Song, LEI Rong

2016, 45(10):  1241-1249.  doi:10.11947/j.AGCS.2016.20150651

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Influenced by large elevation variation, traditional ortho stereo image production method for complex terrain regions usually results in insufficient local stereoscopic or diplopia, and thus causes visual fatigue. In order to solve the problem, we introduce a depth mapping model, design a nonlinear mapping function, and according to the actual area elevations, adaptive preprocess height transformation. And then, through iterative and per-pixel solution with parallax function, stereo images are finally generated. Finally, we provide an algorithm or a process which can adaptive fast generate stereoscopic images.

Position Clustering for Polygon Object under Dual-constrains

YU Li, GAN Shu, YUAN Xiping, LI Jiatian

2016, 45(10):  1250-1259.  doi:10.11947/j.AGCS.2016.20150491

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It is a vital research direction for spatial clustering to recognize polygon cluster, but due to the dual-constrains by geometric information of polygons and obstacles, the position similarity of polygon is difficult to calculate accurately and quickly.A polygon clustering algorithm under dual-constrains is proposed by extending the algorithm of multi-scale spatial clustering, and constructing an intensity function to express position aggregation between object and its adjacent object. For further discuss, it takes the same thresholds of intensity function in adjacent scales as convergence condition. Simulated polygons and real data are chosen to perform clustering in experiments to verify the validity of our algorithm. Results show that without predefined parameters, this algorithm can identify variety polygon clusters with different densities, arbitrary shape, bridge and obstacle.

A Semantics-aware Self-adaptive Associated Organization Method of GeoVideo Big Data

XIE Xiao

2016, 45(10):  1260-1260.  doi:10.11947/j.AGCS.2016.20160327

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