Table of Content

20 June 2016, Volume 45 Issue 6

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Determination of Ocean Tide Loading Displacements Using Kinematic PPP

ZHANG Xiaohong, MA Lan, LI Pan

2016, 45(6):  631-638.  doi:10.11947/j.AGCS.2016.20150327

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In this study, 12 GPS stations' continuous observations from 2007 to 2012 were utilized to determine ocean tide loading (OTL) displacements by kinematic PPP. Through comparison of estimates from kinematic PPP and results predicted by 7 global ocean tide models, one regional model and static PPP, TPXO.7.2, EOT11a, HAMTIDE and NAO99Jb were found having smaller RMS misfits than other models. Comparing the RMS misfits of static PPP results with that of models, we found that they have similar patterns except for the east direction of S₂, K₂ and K₁ and north direction of M₂ and N₂, in which the static PPP's RMS misfits are a little bit larger than models'. Furthermore, apart from K₁ and K₂, the RMS misfits between Kinematic PPP and model estimates are less than 1 mm and 2.5 mm in horizontal and vertical directions, which reach the same precision of static PPP. Obvious system bias was found between the results of kinematic PPP and NAO99Jb model. After subtracting the system bias, all constituents' RMS misfits decreased evidently, especially for K₁ constituent's vertical component, reducing from 16.4 mm to 1.3 mm. Moreover, by comparing the harmonic parameters estimated from tide gauge data and ocean tide models, we found results from gauge data also agree best with TPXO.7.2, EOT11a, HAMTIDE and NAO99Jb, which demonstrates that kinematic PPP is capable of determining OTL displacements and also indicates that these models are more applicable for Hong Kong.

Performance Analysis of BDS Satellite Orbits during Eclipse Periods: Results of Satellite Laser Ranging Validation

PENG Hanbing, YANG Yuanxi, WANG Gang, HE Haibo

2016, 45(6):  639-645.  doi:10.11947/j.AGCS.2016.20150637

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The performance of BeiDou satellite orbits during eclipse periods is an important part of the performance analysis of BeiDou Navigation Satellite System (BDS). Accuracy evaluation of satellite orbits in ephemeris of BDS during eclipse periods can provide support for the service performance assessment. It also helps to find possible deficiencies in the orbit modeling during eclipse periods, which may further contribute to the improvements of functional models for precise orbit determination. The effects of eclipse periods on the orbits of the three types of satellites of BDS are analyzed with the satellite laser ranging (SLR) observations ranging from January 2014 to July 2015. At the same time, the orbit radial accuracy of BDS broadcast and precise ephemeris are validated. The results show that, obvious orbit accuracy decrease can be observed in both broadcast and precise ephemeris for IGSO/MEO satellites during eclipse periods (especially the yaw-maneuver periods). And orbit radial errors of IGSO/MEO satellites in broadcast ephemeris reach 1.5~2.0 m, and exceed 10.0 cm for that in precise ephemeris. Performance decrease of the GEO satellite orbit during eclipse arcs can hardly be revealed by the orbit radial residual series. During non-eclipse periods, radial accuracy of IGSO/MEO and GEO satellite orbits in broadcast ephemeris are better than 0.5 m and 0.9 m respectively. The radial accuracy of IGSO/MEO satellite orbits in precise ephemeris are better than 10.0 cm and that of the GEO satellite is about 50.0 cm with a systematic bias of 40.0 cm around.

Prediction of Navigation Satellite Clock Bias Considering Clock's Stochastic Variation Behavior with Robust Least Square Collocation

WANG Yupu, LÜ Zhiping, WANG Ning, LI Linyang, GONG Xiaochun

2016, 45(6):  646-655.  doi:10.11947/j.AGCS.2016.20150569

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In order to better express the characteristic of satellite clock bias (SCB) and further improve its prediction precision, a new SCB prediction model is proposed, which can take the physical feature, cyclic variation and stochastic variation behaviors of the space-borne atomic clock into consideration by using a robust least square collocation (LSC) method. The proposed model firstly uses a quadratic polynomial model with periodic terms to fit and abstract the trend term and cyclic terms of SCB. Then for the residual stochastic variation part and possible gross errors hidden in SCB data, the model employs a robust LSC method to process them. The covariance function of the LSC is determined by selecting an empirical function and combining SCB prediction tests. Using the final precise IGS SCB products to conduct prediction tests, the results show that the proposed model can get better prediction performance. Specifically, the results' prediction accuracy can enhance 0.457 ns and 0.948 ns respectively, and the corresponding prediction stability can improve 0.445 ns and 1.233 ns, compared with the results of quadratic polynomial model and grey model. In addition, the results also show that the proposed covariance function corresponding to the new model is reasonable.

Comparison of Several Methods for Outlier Estimation

LU Tieding

2016, 45(6):  656-662.  doi:10.11947/j.AGCS.2016.20130745

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Computational problem of gross errors estimation is discussed based on the mean shift model, and the gross errors estimation formulas of the observed statistical correlation data snooping method are given. The relationships of gross errors estimation of the data snooping method, the method of simultaneous locating and evaluating multidimensional gross errors (LEGE), quasi-accurate detection of gross errors (QUAD) method and the partial least-squares (PLS) method are discussed. It is proved that ① in the case of correlated observations, calculation of gross errors estimation of the PLS method and the QUAD method are equivalent. However, these two methods are different with the data snooping method and the LEGE method; ② in the case of uncorrelated and unequal weight observations, calculation of gross errors estimation of the QUAD method, the PLS method and the data snooping method are equivalent, but these three methods are different with the LEGE method; ③ in the case of uncorrelated and equal weight observations, calculation of gross errors estimated value of these four methods are equivalent. Finally, the case studies verify the conclusions.

Method of Multi-dimensional Gross Errors Snooping of GPS Velocity Estimation in Airborne Gravimetry

ZHENG Kai, LIU Zhanke, XIAO Xuenian, ZHANG Xiaohong

2016, 45(6):  663-669.  doi:10.11947/j.AGCS.2016.20150481

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Precision velocity plays an important role in airborne gravimetry. Since the aircraft in a state of stable flight, we could establish a strict state equation with constant acceleration model for it, then obtained predicted velocity which was used for constructing a priori residual Q to detect the gross errors. Theoretical research showed that Q was influenced by the accuracy of predicted velocity and the measurement errors. According to the statistical features of Q combined with IGG Ⅲ principle, we could lower the contribution of the observation that contained the gross errors. Static testing was used for analyzing the characteristic of measurement errors as well as the accuracy of predicted velocity under the simulated ideal flight environment where the acceleration was approximate to a constant, the results also showed the relationship between the sampling rate and the ability of detecting gross errors. Both the static and kinematic tests demonstrate that new method can well detect the gross error smaller than 1 cycle.

Ill-conditioned Problems Robust Solution of Improved Fruit Fly Optimization Algorithm Combining with Tikhonov Regularization Method

FAN Qian, ZHANG Ning

2016, 45(6):  670-676.  doi:10.11947/j.AGCS.2016.20150606

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Based on deeply analysis for optimization process of basic fruit fly optimization algorithm, an improved fruit fly optimization (IFOA) algorithm is proposed via changing random search direction and adding to a tuning coefficient of search radius. Moreover, through introducing the regularization term of objective function in IFOA algorithm, a new method that IFOA algorithm is combined with Tikhonov regularization method is put forward in order to resolving ill-conditioned problems. Analysis results of practical example show that solution accuracy of new method is superior to genetic algorithm and single Tikhonov regularization method. When observation contains gross errors, the deviation between the results and the true value will increase rapidly using least square method to solve ill-conditioned problems. At this time, the new method has strong robustness. Compared with intelligent search method represented by genetic algorithm, new method has the characteristics of less parameter, fast calculation speed, simple optimization process. It is more practical in ill-conditioned problems solution.

Position and Pose Estimation of Spherical Panoramic Image with Improved EPnP Algorithm

DENG Fei, WU Yousi, HU Yulei, CUI Hongxia

2016, 45(6):  677-684.  doi:10.11947/j.AGCS.2016.20150411

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Spherical panoramic imaging can overcome the limitations of perspective imaging's range of view and achieve three-dimensional reconstruction and measurement with full coverage.The EPnP(efficient perspective-n-point) algorithm fit for ordinary image's position and pose estimation is improved and extended by this paper to put forward a robust and fast method to estimate spherical panoramic image's position and pose. Firstly,we construct the projection model of spherical panoramic image to extend the perspective plane imaging model of EPnP algorithm to the spherical imaging model;then with the improved EPnP algorithm basing on the condition equation that panoramic sphere center,image point and control point are collinear, we obtain the control points' coordinates in spherical panoramic image space; finally, we solve the spherical panoramic image's position and pose directly with the Horn absolute positioning algorithm. Compared with the position and pose estimation method of spherical panoramic image with the resection algorithm, the experiment results show that the method proposed in this paper can achieve higher robustness, higher efficiency without going through an iterative solution, and it can also achieve high accuracy with a few control points.Based on the panoramic camera stitching with non-strict center, the reprojection error can be controlled around 3.00 pixel level.

Calibration for Relative Interior Orientation Relationship and Band-to-band Registration with High Accuracy of ZY-3 Multi-spectral Image

LI Qijun, FAN Dazhao, LEI Rong, JI Song, ZHANG Wenzhao

2016, 45(6):  685-690.  doi:10.11947/j.AGCS.2016.20150363

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Using high accuracy match points extracted between the multi-spectral images that obtained at the same time,a position model of the CCD chips of the ZY-3 multi-spectral camera was proposed. Relative interior orientation relationship parameters were calculated and accurate band-to-band automatic registration of ZY-3 multi-spectral image was achieved based on the position model. The experimental result indicates that the band-to-band automatic registration accuracy of ZY-3 multi-spectral image is better than 0.3 pixels with the proposed method.

Quantitative Analysis in Frequency Domain and Determination of Spatial Resolution in Image Fusion

DUAN Wei, YAN Li

2016, 45(6):  691-697.  doi:10.11947/j.AGCS.2016.20150146

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Image fusion is one of the important steps to obtain high quality images.In this paper, the variation of signal frequency in image fusion is given according to the relationship between Nyquist frequency of high sampling rate,Nyquist frequency of low sampling rate and signal frequency.Then the frequency of the fused images is quantifying and the spatial resolution of the image is determined based on the the variation of signal frequency in image fusion.The high frequency information in the high resolution image is the information with the frequency between the Nyquist frequency of high sampling rate and the Nyquist frequency of low sampling rate.Finally, some fusion methods and remote sensing images are used to validate the proposed method. The experimental results show that the results obtained are consistent with the results of the experiment.

An Aerial Image Mosaic Method Based on UAV Position and Attitude Information

CHENG Zhenggang, ZHANG Li

2016, 45(6):  698-705.  doi:10.11947/j.AGCS.2016.20150567

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As the existing methods for aerial image mosaic take high computational, a fast and effective algorithm based on the position and attitude information of unmanned aerial vehicles (UAV) is proposed. Firstly, the coordinates and attitude angles of UAV can be obtained by airborne GPS and inertial measurement unit (IMU), and each aerial image has a corresponding position and attitude information. The homography matrix between two aerial images with the positions and attitude information can be calculated. Then the registration of the mosaic images is obtained by the operation of homography matrix. Finally, the multiple images can be stitched and the whole panorama got. A large number of experiments demonstrate this algorithm is efficient.

Stripes Elimenation and Registration of Large Aperture Static Imaging Spectrometer Image

WANG Fubei, JING Juanjuan, WU Qiongshui, ZHOU Jinsong

2016, 45(6):  706-712.  doi:10.11947/j.AGCS.2016.20150375

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The images obtained by large aperture static imaging spectrometer(LASIS) are two dimensional images which contain interference information. The acquisition of the interferogram needs to pushbroom the whole field of view. The pose error of the platform can result in the error of the interferogram extraction, and then affect the accuracy of the recovered spectrum. Therefore, the image registration is the key link of the interferogram extraction. The accuracy of the existed registration methods applied to LASIS images is limited as the images are modulated by the interference stripes. In order to reduce the interference effect of the stripes in image registration, a stripe pattern is optimized in this paper to eliminate the stripes in LASIS images. Then, the frequency domain image registration method is used to realize the precise registration of LASIS image. Results show that this method eliminates the influence of interference stripes, the registration accuracy can reach up to 0.0294 pixels. Compared with the existed registration methods for LASIS, the accuracy improved 45.48% along the track direction, 52.22% in cross track direction, and image rotation accuracy improved 39.13%.

Application of High-resolution PS-InSAR in Deformation Characteristics Probe of Urban Rail Transit

QIN Xiaoqiong, YANG Mengshi, WANG Hanmei, YANG Tianliang, LIN Jinxin, LIAO Mingsheng

2016, 45(6):  713-721.  doi:10.11947/j.AGCS.2016.20150440

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In order to make sure the security and sustainable development of the urban rail transit, the PS-InSAR technology is introduced into the deformation monitoring of urban rail transit. Taking Shanghai as an example, it is analyzed that the characteristics of surface deformation along the rail transit. Firstly, 26 TerraSAR-X images are used to carry out the high-resolution PS-InSAR subsidence fine measurements in Shanghai for the overall land subsiding characteristics of rail transit. Then, the detail subsidence pattern and the driving force is discussed by classified the rail transit with different construction periods and building modes. Finally, the accuracy of the results is verified by leveling in the same period. The results show that rapid urbanization construction has become a main reason for the subsidence of Shanghai rail transit. Rail transit with different construction periods and building modes show various deformation characteristics. Earlier sections are more stable than later sections and elevated sections have smaller subsidence rate than underground sections. The verification results show fairly consistent agreement. The results further illustrate that it is feasible to use the high-resolution PS-InSAR technology into the deformation monitoring, management, maintenance and early warning of urban public transportation projects. It can also provide decision support for planning and construction of urban public transportation.

Topological Relation Representation Model between Regions with Holes

SHEN Jingwei, ZHOU Tinggang, ZHU Xiaobo

2016, 45(6):  722-730.  doi:10.11947/j.AGCS.2016.20150352

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In order to study the topological relation between regions with holes, a topological relation representation model named 25IM(25 intersection model) is proposed. Based on point set theory, interior, boundary and exterior of spatial object are defined. The shortcoming of 9IM(9 intersection model) between regions with holes is analyzed. A region with holes can be separated into five parts including interior, outer boundary, inner boundary, exterior outside the outer boundary, and exterior within the inner boundary. Then, 5×5 matrix model named 25IM between two regions with holes are defined. Eight rules are defined to exclude the illogical topological relations. Eight basic topological relations, including disjoint, meet, overlaps, covers, contains, equal, coveredby and Inside, are described in detail by using 25IM. It can be concluded that the proposed 25IM can express the topological relation between regions with holes in more detail.

A Method of Generating Indoor Map Spatial Data Automatically from Architectural Plans

SUN Weixin, WANG Guangxia, ZHANG Jinming, YOU Tian

2016, 45(6):  731-739.  doi:10.11947/j.AGCS.2016.20150658

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Taking architectural plans as data source, we proposed a method which can automatically generate indoor map spatial data. Firstly, referring to the spatial data demands of indoor map, we analyzed the basic characteristics of architectural plans, and introduced concepts of wall segment, adjoining node and adjoining wall segment, based on which basic flow of indoor map spatial data automatic generation was further established. Then, according to the adjoining relation between wall lines at the intersection with column, we constructed a repair method for wall connectivity in relation to the column. Utilizing the method of gradual expansibility and graphic reasoning to judge wall symbol local feature type at both sides of door or window, through update the enclosing rectangle of door or window, we developed a repair method for wall connectivity in relation to the door or window and a method for transform door or window into indoor map point feature. Finally, on the basis of geometric relation between adjoining wall segment median lines, a wall center-line extraction algorithm was presented. Taking one exhibition hall's architectural plan as example, we performed experiment and results show that the proposed methods have preferable applicability to deal with various complex situations, and realized indoor map spatial data automatic extraction effectively.

Auto-selection of Areal Habitation Based on Analytic Hierarchy Process

HU Huiming, QIAN Haizhong, HE Haiwei, WANG Xiao, CHEN Jingnan

2016, 45(6):  740-746.  doi:10.11947/j.AGCS.2016.20150078

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Considering the influencing factors in habitation selection, such as its administrative scale, location feature, area size and so on, a new method of areal habitation auto-selection was proposed based on the analytic hierarchy process (AHP). Firstly, standardize the factors influencing the importance of habitation; then adopt the AHP method to construct hierarchical structure model for one habitation by using these factors, and make these factors correlate with each other; on this basis, the weight of each factors was calculated and the importance of each habitation on the map was comprehensively evaluated; finally, use square root model to complete the habitation selection. The proposed method combined the qualitative analysis with quantitative analysis, and synthetically take into account the difference that different factors have different influence on habitation importance, which improved the scientificalness of weights allocation. Experiment showed that the selecting results of this method are in conformity with the selection rules, and solved the problem of which to choose in the habitation selection.

A Displacement Algorithm Based on Geometry Similarity for Spatial Conflicts between Roads and Buildings

LI Zhenhao, YANG Chuncheng, WEI Bin, ZHOU Xiaodong, HE Liesong, XIN Rui

2016, 45(6):  747-755.  doi:10.11947/j.AGCS.2016.20150559

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Keeping the consistency of spatial distribution patterns of buildings has been a difficulty in the problem of spatial conflicts resolution between roads and buildings. The relationships between roads and buildings are classified into types of Open Block, Half-open Block and Close Block based on the extent that roads encircle buildings. An algorithm for buildings displacement is proposed based on geometry similarity which is realized by constraints of distance, angle and area. The skeleton of buildings in a road mesh is constructed by means of MST whose characteristics of length and angle are regarded as distance and angle constraints for buildings displacement. And area ratios of all buildings to corresponding road mesh are regarded as the area constraints for buildings displacement. Series of secondary conflict disposal methods are explored for the possible secondary conflicts. Experimental results show conflicts between roads and buildings are eliminated and spatial distribution pattern of buildings is maintained completely.

Theory and Method for Detecting Abnormal Crustal Deformation Using GNSS

XU Keke

2016, 45(6):  756-756.  doi:10.11947/j.AGCS.2016.20160152

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