Acta Geodaetica et Cartographica Sinica

Low-frequency Errors Compensation of Attitude Determination System in Satellite Photogrammetry

WANG Renxiang, WANG Jianrong, HU Xin

2016, 45(2): 127-130. doi:10.11947/j.AGCS.2016.20150167

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In the attitude determination system exists not only the high-frequency errors, but also the low-frequency errors related to the satellite orbit latitude and time. The low-frequency errors would affect the location accuracy without GCPs, especially to the horizontal accuracy. In this paper, firstly, the factors that produce low-frequency errors and the solutions are analyzed. Secondly, the low-frequency errors are detected and compensated automatically during bundle adjustment in TH-1 satellite, thus the influence of location accuracy by low-frequency error is eliminated. At last, the verification is tested using data of TH-1. The experimental results show: low-frequency errors compensation can resolve the system error of position without GCP, and has played an important role in the consistency of global location accuracy for TH-1.

Solution Method and Precision Analysis of Double-difference Dynamic Precise Orbit Determination of BeiDou Navigation Satellite System

LIU Weiping, HAO Jinming, TIAN Yingguo, YU Heli, ZHANG Kang

2016, 45(2): 131-139. doi:10.11947/j.AGCS.2016.20150190

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To resolve the high relativity between the transverse element of GEO orbit and double-difference ambiguity, the classical double-difference dynamic method is improved and the method, which is to determine precise BeiDou satellite orbit using carrier phase and pseudo-range smoothed by phase, is proposed. The feasibility of the method is discussed and the influence of the method about ambiguity fixing is analyzed. Considering the characteristic of BeiDou, the method, which is to fix double-difference ambiguity of BeiDou satellites by QIF, is derived. The real data analysis shows that the new method, which can reduce the relativity and assure the precision, is better than the classical double-difference dynamic method. The result of ambiguity fixing is well by QIF, but the ambiguity fixing success rate is not high on the whole. So the precision of BeiDou orbit can't be improved clearly after ambiguity fixing.

A Method for Estimating BeiDou Inter-frequency Satellite Clock Bias

LI Haojun, LI Bofeng, WANG Jiexian, XU Tianhe

2016, 45(2): 140-146. doi:10.11947/j.AGCS.2016.20150226

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A new method for estimating the BeiDou inter-frequency satellite clock bias is proposed, considering the shortage of the current methods. The constant and variable parts of the inter-frequency satellite clock bias are considered in the new method. The data from 10 observation stations are processed to validate the new method. The characterizations of the BeiDou inter-frequency satellite clock bias are also analyzed using the computed results. The results of the BeiDou inter-frequency satellite clock bias indicate that it is stable in the short term. The estimated BeiDou inter-frequency satellite clock bias results are molded. The model results show that the 10 parameters of model for each satellite can express the BeiDou inter-frequency satellite clock bias well and the accuracy reaches cm level. When the model parameters of the first day are used to compute the BeiDou inter-frequency satellite clock bias of the second day, the accuracy also reaches cm level. Based on the stability and modeling, a strategy for the BeiDou satellite clock service is presented to provide the reference of our BeiDou.

A New Block Processing Algorithm of LLL for Fast High-dimension Ambiguity Resolution

LIU Wanke, LU Liguo, SHAN Hongyu

2016, 45(2): 147-156. doi:10.11947/j.AGCS.2016.20150370

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Due to high dimension and precision for the ambiguity vector under GNSS observations of multi-frequency and multi-system, a major problem to limit computational efficiency of ambiguity resolution is the longer reduction time when using conventional LLL algorithm. To address this problem, it is proposed a new block processing algorithm of LLL by analyzing the relationship between the reduction time and the dimensions and precision of ambiguity. The new algorithm reduces the reduction time to improve computational efficiency of ambiguity resolution, which is based on block processing ambiguity variance-covariance matrix that decreased the dimensions of single reduction matrix. It is validated that the new algorithm with two groups of measured data. The results show that the computing efficiency of the new algorithm increased by 65.2% and 60.2% respectively compared with that of LLL algorithm when choosing a reasonable number of blocks.

The Application of Adaptive Federated Filter in GPS-INS-Odometer Integrated Navigation

LI Zengke, WANG Jian, GAO Jingxiang, YAO Yifei

2016, 45(2): 157-163. doi:10.11947/j.AGCS.2016.20140530

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In multi-sensor integrated navigation, extensive observation information, low computational efficiency and weak robust ability will lead to poor navigation performance. An adaptive federated filter is proposed and applied in GPS-INS-Odometer integrated navigation. First the dynamical model and observation model of GPS-INS-Odometer integrated navigation are introduced. Information allocation factor and adaptive factor are compared to find out their common characteristic. The equivalence property between federated filter and adaptive filter is proved and the condition of equivalence is built. The information allocation factor of adaptive federated filter is constructed. Finally an actual calculation was performed to test the validity of new algorithm. The results of the experiment indicate that compared with the information allocation factor constructed by initial variance of GPS and Odometer in classical federated filter, adaptive federated filter shows well robust performance and high computational efficiency. It can weaken the influence of multi-sensor dynamical model disturbance on navigation resolution. The proposed method plays a positive role in improving the accuracy of directly measurable parameters and indirectly measurable parameters.

Distribution Analysis of Multi GNSS Slant Delays and Simulated Water Vapor Tomography in Yangtze River Delta

WANG Wei, SONG Shuli, WANG Jiexian, CHEN Qinming, ZHU Wenyao, YE Biwen

2016, 45(2): 164-169. doi:10.11947/j.AGCS.2016.20140648

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Currently, the GNSS network of Yangtze River delta has being applied to monitor the water vapor above this region and research water vapor tomography. Studies have shown that the dictances between stations are large and inhomogeneous, that will make it difficult to get the high tomography precision. Therefore, a simulation test of multi GNSS observations on tomography is introduced. The multi GNSS observations are more homogeneous in spatial distribution than a single positioning system, which can reduce the space rate of the grid, especially increase the number of the grid with information at middle and high layers. The multi GNSS observation can provide more and better water vapor information which can patch up deficiency of a single positioning system. A simulated water vapor tomography is carried out, and the result shows that the multi GNSS observations could improve the accuracy of tomography, especially above the 5 km height layer of the atmosphere.

Bandwidth Optimization of Normal Equation Matrix in Bundle Block Adjustment in Multi-baseline Rotational Photography

WANG Xiang, ZHANG Yongjun, HUANG Shan, XIE Xunwei

2016, 45(2): 170-177. doi:10.11947/j.AGCS.2016.20150282

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A new bandwidth optimization method of normal equation matrix in bundle block adjustment in multi-baseline rotational close range photography by image index re-sorting is proposed. The equivalent exposure station of each image is calculated by its object space coverage and the relationship with other adjacent images. Then, according to the coordinate relations between equivalent exposure stations, new logical indices of all images are computed, based on which, the optimized bandwidth value can be obtained. Experimental results show that the bandwidth determined by our proposed method is significantly better than its original value, thus the operational efficiency, as well as the memory consumption of multi-baseline rotational close range photography in real-data applications, is optimized to a certain extent.

Interest Point Detection for Multispectral Remote Sensing Image Using Phase Congruency in Illumination Space

CHEN Min, ZHU Qing, ZHU Jun, XU Zhu, HUANG Lanxin

2016, 45(2): 178-185. doi:10.11947/j.AGCS.2016.20150030

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A robust interest point detection algorithm based on illumination space and phase congruency is proposed in this paper. Firstly, image illumination space is constructed by using a parameters adaptive method. Secondly, a phase congruency based interest point detection algorithm is adopted to compute candidate points in illumination space. Then, all interest point candidates are mapped back to the original image and a non-maximum suppression step is added to find final interest points. Finally, the feature scale values of all interest points are calculated based on the Laplacian function. The proposed algorithm combines the advantages of illumination space and phase congruency, which makes the proposed method robust to the radiation variation of multispectral images. The experimental results show that the proposed method performs better than other traditional methods in feature repeatability rate and repeated features number.

Dual Quaternion Method to Solve Exterior Orientation Parameters for Satellite Linear Array Images

YU Anzhu, JIANG Ting, GONG Hui, GUO Wenyue, JIANG Gangwu

2016, 45(2): 186-193. doi:10.11947/j.AGCS.2016.20140643

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According to the characteristics that dual quaternion can describe the position and orientation simultaneously, a method using dual quaternion to calculate the exterior orientation parameters for satellite linear array images is proposed. In this method the real part of dual quaternion is used to represent attitude of the sensor, and both the real part and the dual part are used to represent the position of the sensor.The model describing exterior parameters is established by interpolating the position and attitude. To reduce calculation, the simplified spherical linear interpolation algorithm is proposed, and the geometric model is established.In order to calculate the exterior parameters, the collinear equation is linearized at first. Then the virtual observation equations for position parameters are deduced according to the theory of matrix derivative, and the weight of the equation is calculated using error propagation principle. The exterior orientation parameters are calculated iteratively using parameter adjustment with constraints at last. Experimental results indicate that the proposed method is reliable and correct, and the precision of parameter estimation is higher than traditional methods using Euler angles or unit quaternion. The necessity of accuracy initial values and virtual observation equations for calculating exterior parameters is also revealed.

Satellite Video Stabilization with Geometric Distortion

WANG Xia, ZHANG Guo, SHEN Xin, LI Beibei, JIANG Yonghua

2016, 45(2): 194-198. doi:10.11947/j.AGCS.2016.20150238

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There is an exterior orientation difference in each satellite video frame, and the corresponding points have different image locations in adjacent frames images which has geometric distortion. So the projection model, affine model and other classical image stabilization registration model cannot accurately describe the relationship between adjacent frames. This paper proposes a new satellite video image stabilization method with geometric distortion to solve the problem, based on the simulated satellite video, we verify the feasibility and accuracy of proposed satellite video stabilization method.

Soil Moisture Retrieval Using Reflected Signals of BeiDou GEO Satellites

ZOU Wenbo, ZHANG Bo, HONG Xuebao, YANG Dongkai, CUI Zhaoyun

2016, 45(2): 199-204. doi:10.11947/j.AGCS.2016.20150135

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This paper proposes a method of continuous long-term soil moisture measurement using signals from BeiDou GEO satellites. It also presents the soil moisture inversion model as well as the relevant signal processing steps. Moreover, a land-based experiment is carried out to verify its validity. This method adopts the dual-antenna Global Navigation Satellite System Reflection (GNSS-R) mode to receive and process direct signal from BeiDou GEO satellites and reflected signal from soil. Based on signal synchronization, the reflectivity of soil can be calculated according to the extracted signal power values. And then, the soil moisture can be obtained in light of the inversion model. By taking singals from BeiDou GEO satellites, not only the positioning calculation step of general GNSS-R data processing can be ignored, but also a continuous long-term observation of soil moisture for fixed area can be realized. Experiment results based on the method above show a good continuity in both time and magnitude. They are also highly consistent with reference values and the root mean square error equals to 0.049. Compared with BeiDou IGSO and GPS MEO satellites, BeiDou GEO satellites can present a better performance in soil moisture retrieval.

Tracking Road Centerlines from Remotely Sensed Imagery Using Mean Shift and Kalman Filtering

CAO Fanzhi, ZHU Shulong, ZHU Baoshan, LI Runsheng, MENG Weican

2016, 45(2): 205-212. doi:10.11947/j.AGCS.2016.20140610

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Road tracking based on template matching is one class of practical methods of road extraction. However, the conventional methods of template matching mainly utilize correlation coefficient as the similarity measure. As a result, these algorithms are sensitive to occlusions caused by vehicles and trees and are unsuitable for road extraction from high-resolution remotely sensed imagery. To address this problem, this paper designs a road center matching algorithm based on mean shift utilizing a robust similarity measure, which overcomes the sensitivity of correlation coefficient matching to occlusions; then Kalman filter is utilized to track road centerlines from high-resolution remotely sensed imagery. Experimental results demonstrate that the proposed method can extract road centerlines from high-resolution remotely sensed imagery accurately and is robust to occlusions caused by vehicles and trees.

A Multi-platform MC-SBAS Method for Extracting Long-term Ground Deformation

DENG Lin, LIU Guoxiang, ZHANG Rui, WANG Xiaowen, YU Bing, TANG Jia, ZHANG Heng

2016, 45(2): 213-223. doi:10.11947/j.AGCS.2016.20140614

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The satellite multi-temporal radar interferometry technology has been often widely used to monitor the regional ground deformation. However, due to the limitations of the lifetime and revisit cycle, a single satellite platform cannot provide sufficient data sources for estimating and analyzing the long-time deformation monitoring (e.g. spanning 5 to 10 years). In order to extend the time span of deformation monitoring, this paper proposes the model-constrained small baseline subset (MC-SBAS) method by using the multi-platform SAR images. This method can integrate the SAR datasets from different satellites and improve the efficiency of deformation monitoring. The validation is performed by taking the Southern California as the study area and using 10 ERS SAR images (acquired between 2002 and 2005) and 20 EnviSat ASAR images (acquired between 2004 and 2008). In this validation, the spatiotemporal deformation information with the extending time span of 6.5 years in the study area is extracted by the MC-SBAS method, thus extending the time span of deformation tracking to 6.5 years. The quality of deformation results derived from both MC-SBAS and the conventional SBAS method is assessed and compared by using the ground truth data obtained from the 6 GPS tracking stations. The validation result shows that the root mean squared error (RMSE) between the MC-SBAS and GPS results is 8.7 mm, which is less than the RMSE between the SBAS and GPS results (11.7 mm). In addition, the continuity and accuracy in the deformation time series derived from MC-SBAS are improved remarkably.

Establishment of the Comprehensive Shape Similarity Model for Complex Polygon Entity by Using Bending Mutilevel Chord Complex Function

CHEN Zhanlong, QIN Mengjiao, WU Liang, XIE Zhong

2016, 45(2): 224-232. doi:10.11947/j.AGCS.2016.20140633

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A method about shape similarity measurement of complex holed objects is proposed in this paper. The method extracts features including centroid distance, multilevel chord length, bending degree and concavity-convexity of a geometric object, to construct complex functions based on multilevel bending degree and radius. The complex functions are capable of describing geometry shape from entirety to part. The similarity between geometric objects can be measured by the shape descriptor which is based on the fast Fourier transform of the complex functions. Meanwhile, the matching degree of each scene of complex holed polygons can be got by scene completeness and shape similarity model. And using the feature of multi-level can accomplish the shape similarity measurement among complex geometric objects. Experimenting on geometric objects of different space complexity, the results match human's perceive and show that this method is simple with precision.

A Permutation Test for Identifying Significant Clusters in Spatial Dataset

TANG Jianbo, LIU Qiliang, DENG Min, HUANG Jincai, CAI Jiannan

2016, 45(2): 233-240. doi:10.11947/j.AGCS.2016.20140605

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Spatial hierarchical clustering methods considering both spatial proximity and attribute similarity play an important role in exploratory spatial data analysis. Although existing methods are able to detect multi-scale homogeneous spatial contiguous clusters, the significance of these clusters cannot be evaluated in an objective way. In this study, a permutation test was developed to determine the significance of clusters discovered by spatial hierarchical clustering methods. Experiments on both simulated and meteorological datasets show that the proposed permutation test is effective for determining significant clustering structures from spatial datasets.

Determination of Circumcenter of Triangle on Ellipsoidal Surface Based on Map Algebra

JIANG Huiping, TAN Shudong, HU Hai

2016, 45(2): 241-249. doi:10.11947/j.AGCS.2016.20140503

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The geodesic distances from the circumcenter to 3 vertexes of the triangle on ellipsoidal surface are equal. The ellipsoid-oriented determination of circumcenter of triangle on ellipsoidal surface is applicable when it comes to generation of the Voronoi diagram and construction of the Delaunay triangulation net on the ellipsoidal earth, which can be considered as a solution of significance in computation of geometries and spatial analysis on the ellipsoid. Based on the idea of combining the raster and vector methods and the theory of map algebra, the working process can be described as below: firstly, initiate the geographical distance transformation and create the distance field with a high degree of accuracy; secondly, conduct boundary tracking and matching and then determinate the range of grids where the circumcenter of triangle locates; thirdly, interpolate the initial equidistant point; finally, approximate the circumcenter of triangle on earth ellipsoidal surface by means of numeric calculation. The positioning error of this algorithm is controlled less than 0.001 m within several thousand kilometers range of span. As regards the method proposed in the present paper, its computational efficiency is O(m) where m is the number of pixels in the image, i.e., grid resolution. In conclusion, this algorithm can be considered as both ellipsoid-oriented and not content-related, which is especially appropriate for complex geocomputation globally.

A Supervised Metric Learning Approach for Efficient Aerial Oblique Image Matching Using Neighborhood Information

HU Han

2016, 45(2): 250-250. doi:10.11947/j.AGCS.2016.20150413

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