Table of Content

20 August 2017, Volume 46 Issue 8

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Global Unification Problem of the Height System

XU Houze

2017, 46(8):  939-944.  doi:10.11947/j.AGCS.2017.20170406

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Some fundamental problems on the establishment of the global unified height system, including the geometry and gravity definition of the normal height, the global unification of the regional height systems obtained from leveling measurements, and the determination of geoid potential W₀ are discussed. The main conclusions are summarized:①The definition of normal height in the sense of geometry leveling and gravity theory is different, so that h-ζ≠H^L, here h, ζ and H^L are geodetic height, height anomaly and levelling height respectively. Instead of it, we found H^L=h-ζ+∂γ/∂hζH, in the mountain area, the last correction term have to be added. ②Based on the merging of GNSS/gravity/regional leveling, the regional leveling height can be transformed into a global relative unified height system, however the value of geoid potential W₀ is still needed in order to establish an absolute height system. ③W₀ can be determinated from the modern geodetic techniques with a certain accuracy, but it is time variable, so that people may only define a global absolute unified height system in a fixed epoch.

The Analysis of Height System Definition and the High Precision GNSS Replacing Leveling Method

ZHANG Chuanyin, JIANG Tao, KE Baogui, WANG Wei

2017, 46(8):  945-951.  doi:10.11947/j.AGCS.2017.20170058

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Based on the definition of height system, the gravitational equipotential property of height datum surface is discussed in this paper, differences of the heights at ground points that defined in different height systems are tested and analyzed as well. A new method for replacing leveling using GNSS is proposed to ensure the consistency between GNSS replacing leveling and spirit leveling at mm accuracy level. The main conclusions include:①For determining normal height at centimeter accuracy level, the datum surface of normal height should be the geoid. The 1985 national height datum of China adopts normal height system, its datum surface is the geoid passing the Qingdao zero point.②The surface of equi-orthometric height in the near earth space is parallel to the geoid. The combination of GNSS precise positioning and geoid model can be directly used for orthometric height determination. However, the normal height system is more advantageous for describing the terrain and relief.③Based on the proposed method of GNSS replacing leveling, the errors in geodetic height affect more on normal height result than the errors of geoid model, the former is about 1.5 times of the latter.

The Spherical Harmonic Model of Gravity Field in Mainland China by Slepian Local Spectrum Method

CHEN Shi, XU Weimin, WANG Qianshen

2017, 46(8):  952-960.  doi:10.11947/j.AGCS.2017.20150542

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For the purpose of calculating the gravity field model through spherical harmonic method only based on local measurements, it calculated that the measured gravity field data in mainland China by Slepian local spectrum method, and also it evaluated that the error effected by the non-uniformity of measured points by the known spherical harmonic model of GOCE satellite datasets. Firstly it calculated that the Slepian basis functions in mainland China and took the 72 order spherical harmonic model of GOCE satellite to evaluate the effective of the method in non-uniformity of measured points. Then, it recalculated that the gravity filed model by the Slepian localized spectral approach based on the resample points of Chinese mainland, and determined the gravity field variation model of Chinese mainland using the repeated gravity measure datasets from 2005 to 2008.

Analysis on BDS Satellite Internal Multipath and Its Impact on Wide-lane FCB Estimation

RUAN Rengui, JIA Xiaolin, FENG Laiping

2017, 46(8):  961-970.  doi:10.11947/j.AGCS.2017.20160418

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To the issue of the satellite internal multipath (SIMP) of BeiDou satellites, it proposed and emphasized that the SIMP model should be established as a function of the nadir angle with respect to the observed satellite rather than the elevation of the measurement, so that it can be used for receivers at various altitude. BDS data from global distributed stations operated by the International Monitoring and Assessment System (iGMAS) and the Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) are collected and a new SIMP model as a piece-wise linear function of the nadir angle is released for the IGSO-and MEO-satellite groups and for B1, B2 and B3 frequency band individually. The SIMP of GEO,IGSO and MEO satellites is further analyzed with B1/B2 dual-frequency data onboard the FengYun-3 C(FY3C) satellite at an altitude of~830 km, and it showed that, for nadir angles smaller than 7°, the SIMP values for GEO is quite close to the IGSO's, especially for B2, which may suggest that the SIMP model for IGSO satellites possibly also works for GEO satellites. It also demonstrated that, when the nadir angle is smaller than 12°for the MEO and 7°for the IGSO, the estimated SIMP model with data from FY3C is considerable consistent with that estimated with data collected at ground stations. Experiments are carried out to investigate the impacts of the SIMP on wide-lane fractional cycle bias (FCB) estimation for BDS satellites. The result indicates that, with the correction of the estimated SIMP, the repeatability of the FCB series is significantly improved by more than 60% for all satellites. Specifically, for the MEO and IGSO satellites, the repeatability is smaller than 0.05 cycle; the repeatability of 0.023 and 0.068 cycles achieved for GEO satellites C01 and C02 respectively with the estimated SIMP model for IGSO satellites.

Impact Analysis of Yaw Attitude on BDS Precise Point Positioning

YE Shirong, XIA Fengyu, ZHAO Lewen, XIA Pengfei, CHEN Dezhong

2017, 46(8):  971-977.  doi:10.11947/j.AGCS.2017.20170094

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When the elevation of the Sun with respect to orbital plane is small, the BDS satellite will not track the position of sun and thus will lead to abnormal attitude changing. To avoid this phenomenon, the satellite attitude keeps in orbit-normal mode during the period. The nominal attitude correction methods will affect the calculation of antenna phase center offset and phase wind-up in orbit-normal seasons, and furthermore lead to biases to the position and zenith tropospheric delay(ZTD) estimatedby precise point positioning (PPP). The results of the experiments undergone show that the comprehensive phase wind-up and the satellite antenna phase center errors caused by the incorrect BDS satellite orbit model will exceed 15cm. Compared to the nominal attitude mode,when the orbit-normal attitude mode is adopted, the positioning accuracy in the north, east and up directions will be improved by 53.2%, 54.2%, and 39.3% for dynamic PPP, 61.0%,72.3%,58.4% for static PPP, respectively. Furthermore, the accuracy of ZTD estimated by static PPP will be improved by 33.0%.

A Method for Partial EIV Model with Correlated Observations

WANG Leyang, XU Guangyu, WEN Guisen

2017, 46(8):  978-987.  doi:10.11947/j.AGCS.2017.20160430

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As an extended form of the errors-in-variables(EIV) model, partial errors-in-variables(Partial EIV) model has more advantages than the previous one, such as regular structure, simple solving method, which make it has a wide range of applications. Considering the situation that the correlation between the observations and elements in coefficient matrix is not taken into account in the existed algorithms derived from Partial EIV model, the non-repetitive random elements in the augmented matrix consisting of observation vector and coefficient matrix are extracted to build a more suitable partial EIV model. Based on this model, the special assumptions are extended to the general case where the observations are correlated, a new weighted total least squares(WTLS)algorithms is derived when the observations and elements in coefficient matrix are heteroscedastic and correlated. Through two examples, the algorithm proposed in this paper and the existed algorithms which consider the correlation of the observation in EIV model are compared and analyzed. Research shows that these algorithms can improve the calculation efficiency and more general, especially for the situation that coefficient matrix consists of constant elements and repeated elements.

Determination of Ocean Tide Loading Displacement Parameters by GPS Kinematic PPP

ZHAO Hong, TU Rui, LIU Zhi, JIANG Guangwei

2017, 46(8):  988-998.  doi:10.11947/j.AGCS.2017.20160562

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Due to irregular coastlines, special geological structures and complex submarine topographies, some global ocean tide models exhibit large differences in some specific areas. So that some other geodetic observations have to be used to estimate the ocean tide loading (OTL) under some circumstances as "time-dependent". GPS technique has the advantages of long-term continuous observations, high accuracy and low cost, and GPS precision point positioning (PPP) technique is sensitive to the change of the east, north and vertical component of a station. In this study, it improves that the method in which the 48 OTL displacement parameters estimated in GPS PPP. Then an improved method to estimate 3 time-dependent OTL displacement parameters precisely in PPP is proposed, and the amplitudes and phase lags of eight principal constituents are extracted by the harmonic analysis. 12 GPS stations' continuous observations in Hong Kong from 2006 to 2013 are used to determine three-dimensional OTL displacement by the PPP method. Through comparison of convergence results from static PPP, it is found that the convergence of K1 constituent determined by the method is accelerated in east component. Comparing the RMS misfits between the GPS derived results and the values from the OSU.CHINASEA.2010 ocean tide model, it is found that the constituents' RMS misfits are all less than 1.5 mm in horizontal and vertical directions, except for S2, K2 and K1. Moreover, by comparing the harmonic parameters estimated by GPS derived and tide gauge data with ocean tide models, it is found that the two different observations' results show a great agreement with OSU.CHINASEA.2010 and HAMTIDE2011.11A ocean tide models, which demonstrates that GPS is capable of determining OTL displacement parameters. Using GPS derived 8 constituents' displacements amplitudes and phase lags which were instead of the responding model values to correct OTL can weaken effect of the semiannual signal in GPS long period time series.

Change Detection Method for High Resolution Remote Sensing Images Using Deep Learning

ZHANG Xinlong, CHEN Xiuwan, LI Fei, YANG Ting

2017, 46(8):  999-1008.  doi:10.11947/j.AGCS.2017.20170036

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A novel change detection method is proposed based on deep learning to improve the accuracy of change detection in very high spatial resolution remote sensing images. On the base of image pre-processing, spectral and texture changes are extracted by modified change vector analysis and grey level co-occurrence matrix respectively, both concerning spatial-contextual information. Most likely changed and unchanged pixel-pairs are obtained by an adaptive threshold for selecting the labeled samples. The proposed model based on Gaussian-Bernoulli deep Boltzmann machines with a label layer is built to learn high-level features and is trained for determining the change areas. Experimental results on WorldView-3 and Pléiades-1 show that the proposed method out performs the compared methods in the accuracy of change detection.

A Study on Relative Radiometric Calibration without Calibration Field for YG-25

ZHANG Guo, LI Litao

2017, 46(8):  1009-1016.  doi:10.11947/j.AGCS.2017.20160392

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YG-25 is the first agility optical remote sensing satellite of China to acquire the sub-meter imagery of the earth. The side slither calibration technique is an on-orbit maneuver that has been used to flat-field image data acquired over the uniform calibration field. However, imaging to the single uniform calibration field cannot afford to calibrate the full dynamic response range of the sensor and reduces the efficiency. The paper proposes a new relative radiometric calibration method that a 90-degree yaw maneuver is performed over any non-uniform features of the Earth for YG-25. Meanwhile, we use an enhanced side slither image horizontal correction method based on line segment detector(LSD)algorithm to solve the side slither image over-shifted problem.The shifted results are compared with other horizontal correction method. The histogram match algorithm is used to calculate the relative gains of all detectors. The correctness and validity of the proposed method are validated by using the YG-25 on-board side slither data. The results prove that the mean streaking metrics of relative correction images of YG-25 is better 0.07%, the noticeable striping artifact and residual noise are removed, the calibration accuracy of side slither technique based on non-uniform features is superior to life image statistics of sensor's life span.

Wetland Detection from Multi-sources Remote Sensing Images Based on Probabilistic Latent Semantic Analysis

XU Kai, ZHANG Qianqian, WANG Yanhua, LIU Fujiang, QIN Kun

2017, 46(8):  1017-1025.  doi:10.11947/j.AGCS.2017.20160292

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A novel wetland detection approach for multi-sources remote sensing images was proposed, which based on the probabilistic latent semantic analysis (pLSA). Firstly, spectral, texture, and subclass of wetland were extracted from high-resolution remote sensing image, and land surface temperature and soil moisture of wetland were derived from corresponding multispectral remote sensing image. The feature space of wetland scene was hence formed. Then, wetland scene was represented as a combination of several latent semantics using pLSA, and the feature space of the wetland scene was further described by weight vector of latent semantics. Finally, supporting vector machine (SVM) classifier was applied to detect the wetland scene. Experiments indicated that the adoption of pLSA is able to map the high-dimensional feature space of wetland to low-dimensional latent semantic space. Besides, the addition of subclass and quantitative environment features is able to characterize wetland feature space more effectively and improve the detection accuracy significantly.

GF-4 Images Super Resolution Reconstruction Based on POCS

XU Lina, HE Luxiao

2017, 46(8):  1026-1033.  doi:10.11947/j.AGCS.2017.20170070

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The super resolution reconstruction of GF-4 is made by projection on convex sets (POCS). Papoulis-Gerchberg is used to construct reference frame which can reduce iteration and improve algorithm efficiency.Vandewalle is used to estimate motion parameter which is benefit to block process. Tested and analyzed by real GF-4 series images, it shows that sharpness of super resolution result is positive correlatie to frame amount, and signal to noise ratio (SNR) is negative correlate to frame amount. After processing by 5 frames, information entropy (IE) changes little; sharpness (average gradient) increases from 7.803 to 14.386; SNR reduces a little, from 3.411 to 3.336. The experiment shows that after super resolution reconstruction, sharpness and detail information of results can be greatly improved.

Positioning Correction Algorithm of Vector Road Aided Inertial Navigation Based on the Rough/Fine Matching Method

LI Xiang, HUA Yixin, ZHANG Hong, ZHANG Jiangshui

2017, 46(8):  1034-1046.  doi:10.11947/j.AGCS.2017.20160469

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In the passive environment, accumulated positioning errors of the inertial navigation system (INS) could not be corrected by satellite navigation and positioning, a rough/fine matching method based on high-precision road data was proposed to adjust the vehicle trajectory data acquired by INS. Firstly, by analyzing the feature label point and its minimum bounding rectangle in inertial trajectory, the obvious error matching road and redundant road could be eliminated and the candidate matching road sets could be captured. Then, with the advantages of high precision and stable matching result, the ICCP algorithm was built to compensate and correct the positioning errors caused by INS. Finally, the matching variance and history matching results could be used to judge whether the matching results were correct. Simulation results illustrated that this method could improve the correction accuracy and reduce the false matching results in the complex road intersections.

Dividing and Computing Topological Relations between Complex Regions

WANG Zhangang, DU Qunle, WANG Xianghong

2017, 46(8):  1047-1057.  doi:10.11947/j.AGCS.2017.20160209

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A novel method was proposed for computing topological relations between complex regions based on 9-intersection (9I) matrices. A complex region was composed of a finite set of simple regions and its configuration was represented as a regular expression. Two 9I Boolean matrix operators were defined and used for computing the binary topological relations between complex regions while the relations between the decomposed regions were known. The establishing conditions of the operators were proved and analyzed in detail and the method of eliminating the ambiguities was given to make the computation correct. The approach can be used as a useful computation tool to analysis topological relations between spatial objects with specific configurations. In addition,the operators are dependent on definitions of complex regions and not suitable for regions which violate our definitions.

GIS Data Modeling of a Regional Geological Structure by Integrating Geometric and Semantic Expressions

HE Handong, HU Di, LÜ Guonian, LI Anbo, LI Junli

2017, 46(8):  1058-1068.  doi:10.11947/j.AGCS.2017.20160427

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Using GIS, data models of geology via geometric descriptions and expressions are being developed. However, the role played by these data models in terms of the description and expression of geological structure phenomenon is limited. To improve the semantic information in geological GIS data models, this study adopts an object-oriented method that describes and expresses the geometric and semantic features of the geological structure phenomenon using geological objects and designs a data model of regional geological structures by integrating geometry and semantics. Moreover, the study designs a semantic "vocabulary-explanation-graph" method for describing the geological phenomenon of structures. Based on the semantic features of regional geological structures and a linear classification method, it divides the regional geological structure phenomenon into 3 divisions, 10 groups, 33 classes and defines the element set and element class. Moreover, it builds the basic geometric network for geological elements based on the geometric and semantic relations among geological objects. Using the ArcGIS Diagrammer Geodatabase, it considers the regional geological structure of the Ning-Zhen Mountains to verify the data model, and the results indicate a high practicability.

Study on GNSS Differential Code Biases and Global Broadcast Ionospheric Models of GPS,Galileo and BDS

WANG Ningbo

2017, 46(8):  1069-1069.  doi:10.11947/j.AGCS.2017.20160387

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Study on Multiple Information Fusion of Highway Geological Disaster Emergency and Rapid Monitoring

WU Jifeng

2017, 46(8):  1070-1070.  doi:10.11947/j.AGCS.2017.20170190

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Research on Determination of Marine Gravity Anomalies from Multi-satellite Altimeter Data

ZHANG Shengjun

2017, 46(8):  1071-1071.  doi:10.11947/j.AGCS.2017.20170187

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Hyperspectral Imagery Sparse Unmixing Based on Spatial and Spectral Analysis

WANG Yuqian

2017, 46(8):  1072-1072.  doi:10.11947/j.AGCS.2017.20170167

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