Table of Content

20 September 2015, Volume 44 Issue 8

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The Analytical and Quick Computation Method of Disturbing Gravity in Global and Local Ocean Area

ZHAI Zhenhe, SUN Zhongmiao, WANG Xingtao

2015, 44(8):  827-832.  doi:10.11947/j.AGCS.2015.20140482

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In order to solve the problem of deriving the disturbing gravity from satellite altimetry data, the analytical formula of disturbing gravity computed from geoid and vertical deflection are derived. The analytical formula can be used to get global ocean disturbing gravity by using altimetry data. Considering the existing achievements, the two improved quick computation methods which are respectively according to the global and local area are also get based on the one dimensional FFT algorithm. The quick computation methods can get the same results as the analytical computation and improve the computation speed of 20 times. The precise, quick computation methods can avoid the problem of aliasing and edge effects and have the flexible application. The 2.5' resolution of geoid and vertical deflection derived from EGM2008 model are used to compute the global and local ocean disturbing gravity. The results show that the difference between two method is about 0.8×10^-5 m/s², so the disturbing gravity respectively derived from geoid and vertical deflection are consistent. Considering the actual situation, the disturbing gravity derived from vertical deflection still has some advantages.

MPI Parallel Algorithm in Satellite Gravity Field Model Inversion on the Basis of Least Square Method

ZHOU Hao, LUO Zhicai, ZHONG Bo, LU Biao

2015, 44(8):  833-839.  doi:10.11947/j.AGCS.2015.20140396

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In order to solve the intensive computing tasks and high memory demand problem in satellite gravity field model inversion on the basis of huge amounts of satellite gravity observations, the parallel algorithm for high truncated order and degree satellite gravity field model inversion with least square method on the basis of MPI was introduced. After analyzing the time and space complexity of each step in the solving flow, the parallel I/O, block-organized storage and block-organized computation algorithm on the basis of MPI are introduced to design the parallel algorithm for building design matrix, establishing and solving normal equation, and the simulation results indicate that the parallel efficiency of building design matrix, establishing and solving normal equation can reach to 95%, 68%and 63% respectively. In addition, on the basis of GOCE simulated orbits and radial disturbance gravity gradient data(518 400 epochs in total), two earth gravity models truncated to degree and order 120, 240 are inversed, and the relative computation time and memory demand are only about 40 minutes and 7 hours, 290 MB and 1.57 GB respectively. Eventually, a simulation numerical calculation for earth gravity field model inversion with the simulation data, which has the equivalent noise level with GRACE and GOCE mission, is conducted. The accuracy of inversion model has a good consistent with current released model, and the combined mode can complement the spectral information of each individual mission, which indicates that the parallel algorithm in this paper can be applied to inverse the high truncated degree and order earth gravity model efficiently and stably.

Triple-frequency TurboEdit Cycle-slip Processing Method of Weakening Ionospheric Activity

HUANG Lingyong, ZHAI Guojun, OUYANG Yongzhong, LU Xiuping, WU Taiqi, DENG Kailiang

2015, 44(8):  840-847.  doi:10.11947/j.AGCS.2015.20140380

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The existing triple-frequency cycle-slip detection method usually can not detect and repair the cycle-slip correctly in the ionospheric activity phase or when the magnetic storm happening. To solve the problem, the triple-frequency TurboEdit method for weakening the ionospheric error is advanced based on the dual-frequency TurboEdit method. Both the triple-frequency geometry-free and ionospheric-free combination and second-order time-difference phase geometry-free combination in this algorithm can whittle the influence of ionospheric error effectively. And then, the triple-frequency data is used to validate this algorithm, the experiment results show that this method can weaken the ionospheric error and realize the no-difference dynamicreal-time cycle-slip detection and correction under ionospheric activity phase.

Inertial Aided Kinematic GPS Cycle Slip Detection and Correction for GPS/INS Tightly Coupled System

HAN Houzeng, WANG Jian, LI Zengke

2015, 44(8):  848-857.  doi:10.11947/j.AGCS.2015.20140350

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In order to improve the navigation performance and robustness, a GPS/INS tightly coupled model has been developed, the INS related bias and ionospheric errors were compensated and corrected, the impact of combination observations on cycle slip detection was investigated, and four combinations with the characteristics of longer wavelength, smaller noise and lower ionosphere effect were determined, then an innovative inertial aided adaptive cycle slip detection and correction algorithm based on the selected combination observations was presented, and the impact of INS positioning errors on cycle slip detection has been investigated, the probability of false alarm and success rate of cycle slip correction were utilized to enhance the integrity of cycle slip detection and correction, a new threshold determination criterion was provided to achieve robust cycle slip detection and correction. At last, a field test was utilized to verify and evaluate the performance of the proposed algorithm, multi-cycle slips and GPS gap scenarios were simulated, the results show that the scheme works effectively as long as the complete GPS data outage period is less than 20 second, the performance degrades as the outage period becomes longer; while during the partial data outage durations, the proposed scheme can fix the cycle slips correctly for the simulated 90 second partial outage due to the improved positioning accuracy, a total of 170 dense cycle slips (1 slip per 5 epochs)were introduced, it shows that all introduced cycle slips are successfully detected and the true fixing rate reaches 99.41%.

Present-day Crustal Movement and Strain Rate in Guangxi Area from GPS Data

LIAO Chaoming, MA Yan, PAN Yuanjin, HUANG Xiangxiong

2015, 44(8):  858-865.  doi:10.11947/j.AGCS.2015.20130566

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The 3D crustal movement velocities filed and strain parameters of Guangxi area are acquired in the coordinate frame of ITRF2005 with the multi-period GPS data from 1998 to 2010 analyzed by using GAMIT/GLOBK software, and the area deformation field and present-day construction mechanism are also discussed in this paper. From the GPS monitoring results, the crustal movement of Guangxi area coincides with south China movement in the South-East-East anticlockwise direction, the average vertical velocity value is 33.49 mm/a in ITRF2005 frame, the preponderant direction is N 109.3° E, the average horizon velocity value is +1.30 mm/a, and the trend becomes increasing from East to West of Guangxi province. The present-day strain status is extrusion in N 127.3°±4.8° E direction, the main maximum extrusion strain is -2.7±0.5×10^-9/a with a tension effect in the N 37.3°±4.8° E direction, and the main maximum tension strain is 1.8±0.2×10^-9/a. A more precise 3D present-day crustal velocity filed of Guangxi area is presented in this paper with the full analyzing of GPS data.

Complex Total Least Squares Adjustment

WANG Leyang, YU Dongdong, LÜ Kaiyun

2015, 44(8):  866-876.  doi:10.11947/j.AGCS.2015.20130701

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On the basis of complex least squares adjustment method (CLSAM), the theory of complex total least squares adjustment method (CTLSAM) is proposed. The algorithms of complex total least squares and complex LS-TLS method are derived. Through two examples, the complex LS method under the adjustment criterions that minimize the sum of squares of the module of observation vector residual (adjustment criterion 1) and the sum of squares of the real part and imaginary part of the observation vector (adjustment criterion 2), the complex TLS method under the adjustment criterions that minimize the sum of squares of the module of observation vector and coefficient matrix residual (adjustment criterion 3)and the sum of squares of the real part and imaginary part of the observation vector and coefficient matrix residual (adjustment criterion 4) are compared and analyzed respectively. The results of two examples show that the CLSAM under the adjustment criterion 1 is more reasonable than the adjustment criterion 2; the CTLSAM under the adjustment criterion 3 is more accurate than the adjustment criterion 4; the CTLSAM under the adjustment criterion 3 is better than the CLSAM under the adjustment criterion 1 when the coefficient matrix contains stochastic noise.

A Seam Line Detection Algorithm for Orthophoto Mosaicking Based on Disparity Image

YUAN Xiuxiao, DUAN Mengmeng, CAO Jinshan

2015, 44(8):  877-883.  doi:10.11947/j.AGCS.2015.20140421

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This paper proposes a regional seam line detection algorithm based on the disparity image of the orthophoto. Firstly, the disparity images of the stereo pair are generated by using the SGM (semi-global matching)method, and the small noises are removed through the adaptive threshold. Then, the mathematical morphology method is used to further eliminate the noises and to fill the small holes on the disparity image in order to accurately separate out the non-ground area. Lastly, the seam line is detected using the improved greedy snake algorithm which with better robustness. The experimental result has shown that our method is effective and is able to acquire an optimized seam line that passed around the entities above the ground.

Remote Sensing Image Enhancement Based on Non-subsampled Shearlet Transform and Parameterized Logarithmic Image Processing Model

TAO Feixiang, WU Yiquan

2015, 44(8):  884-892.  doi:10.11947/j.AGCS.2015.20140466

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Aiming at parts of remote sensing images with dark brightness and low contrast, a remote sensing image enhancement method based on non-subsampled Shearlet transform and parameterized logarithmic image processing model is proposed in this paper to improve the visual effects and interpretability of remote sensing images. Firstly, a remote sensing image is decomposed into a low-frequency component and high frequency components by non-subsampled Shearlet transform.Then the low frequency component is enhanced according to PLIP (parameterized logarithmic image processing) model, which can improve the contrast of image, while the improved fuzzy enhancement method is used to enhance the high frequency components in order to highlight the information of edges and details. A large number of experimental results show that, compared with five kinds of image enhancement methods such as bidirectional histogram equalization method, the method based on stationary wavelet transform and the method based on non-subsampled contourlet transform, the proposed method has advantages in both subjective visual effects and objective quantitative evaluation indexes such as contrast and definition, which can more effectively improve the contrast of remote sensing image and enhance edges and texture details with better visual effects.

A Visually Inspired Variational Method for Automatic Image Registration

WANG Huixian, JIN Huijia, LEI Chengqiang, JIANG Wanshou, WANG Yan

2015, 44(8):  893-899.  doi:10.11947/j.AGCS.2015.20140281

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A visually inspired variational method for automatic image registration is proposed to solve local deformation which traditional global registration model cannot well satisfy. The variational model considers local transformation, global smoothness and visual constraints. To account for intensity variations, we incorporate change of local contrast and brightness into our model. Firstly, the data entry of registration model is built according to the root-mean-square error of intensity; secondly, adaptive constraint using H¹ half norm is used to ensure the global smooth in the model; finally, in order to make sure that the spatial attributes of the image satisfy the visual requirements and without distortion, the linear features are used as priori constraints. During the solution of model parameters, the whole image is used to globally estimate the transformation parameters, and then local estimation of the parameters is taken in a small neighbor. The entire procedure is built upon a multi-level differential framework, and the transformation parameters are calculated iteratively, which can consider both global smoothness and local distortion. To assess the quality of the proposed method, ZY-3 satellite images were used. Visual and quantitative analysis proved that the proposed method can significantly improve the registration precision.

Targets Separation and Imaging Method in Sparse Scene Based on Cluster Result of Range Profile Peaks

YANG Qiu, ZHANG Qun, WANG Min, SUN Li

2015, 44(8):  900-908.  doi:10.11947/j.AGCS.2015.20140310

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This paper focuses on the synthetic aperture radar (SAR) imaging of space-sparse targets such as ships on the sea, and proposes a method of targets separation and imaging of sparse scene based on cluster result of range profile peaks. Firstly, wavelet de-noising algorithm is used to preprocess the original echo, and then the range profile at different viewing positions can be obtained by range compression and range migration correction. Peaks of the range profiles can be detected by the fast peak detection algorithm based on second order difference operator. Targets with sparse energy intervals can be imaged through azimuth compression after clustering of peaks in range dimension. What's more, targets without coupling in range energy interval and direction synthetic aperture time can be imaged through azimuth compression after clustering of peaks both in range and direction dimension. Lastly, the effectiveness of the proposed method is validated by simulations. Results of experiment demonstrate that space-sparse targets such as ships can be imaged separately and completely with a small computation in azimuth compression, and the images are more beneficial for target recognition.

Hyperspectral Image Classification Based on the Weighted Probabilistic Fusion of Multiple Spectral-spatial Features

ZHANG Chunsen, ZHENG Yiwei, HUANG Xiaobing, CUI Weihong

2015, 44(8):  909-918.  doi:10.11947/j.AGCS.2015.20140544

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A hyperspectral images classification method based on the weighted probabilistic fusion of multiple spectral-spatial features was proposed in this paper. First, the minimum noise fraction (MNF) approach was employed to reduce the dimension of hyperspectral image and extract the spectral feature from the image, then combined the spectral feature with the texture feature extracted based on gray level co-occurrence matrix (GLCM), the multi-scale morphological feature extracted based on OFC operator and the end member feature extracted based on sequential maximum angle convex cone (SMACC) method to form three spectral-spatial features. Afterwards, support vector machine (SVM) classifier was used for the classification of each spectral-spatial feature separately. Finally, we established the weighted probabilistic fusion model and applied the model to fuse the SVM outputs for the final classification result. In order to verify the proposed method, the ROSIS and AVIRIS image were used in our experiment and the overall accuracy reached 97.65% and 96.62% separately. The results indicate that the proposed method can not only overcome the limitations of traditional single-feature based hyperspectral image classification, but also be superior to conventional VS-SVM method and probabilistic fusion method. The classification accuracy of hyperspectral images was improved effectively.

Semi-supervised Graph-based Hyperspectral Image Classification with Active Learning

TIAN Yanping, TAO Chao, ZOU Zhengrong, YANG Zhaoxia, HE Xiaofei

2015, 44(8):  919-926.  doi:10.11947/j.AGCS.2015.20140221

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Currently, it is difficult and time-consuming to obtain enough labeled samples for hyperspectral image(HSI) classification, while numerous unlabeled samples can be easily identified but unused. Here, in order to overcome these shortcomings, we proposed a semi-supervised graph-based combined with active learning mechanism approach in this paper. Firstly, we extracted the spatio-spectral feature by reorganizing the spectrum of a pixel with its neighbors, followed by a sorting scheme to make the feature representation to be rotation invariant. Then, the most uncertain samples(namely largest ambiguity samples for classifier) were selected for operator to label with active learning algorithm. Finally, both labeled samples and unlabeled samples were used for semi-supervised classification. The proposed algorithm could guarantee that boundary samples were selected, which would help construct the boundary of a classifier. Simultaneously, even when less labeled samples were available, the proposed method achieved a good classification result by introducing a large number of unlabeled samples. The experimental results on three real hyperspectral images confirmed that the proposed method can obtain higher classification accuracy.

Matching Multi-source Areal Habitations with Skeleton Line Mesh of Blank Region

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

2015, 44(8):  927-935.  doi:10.11947/j.AGCS.2015.20140462

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In the large scale map of urban area, obvious difference in geometric position often tend to exist in multisource habitation data, which increases the difficulty and uncertainty of habitation matching. A new matching method for areal habitation by using the skeleton line mesh of blank region is proposed to solve the above problem. Firstly, the one-to-one mapping relationship between skeleton line mesh and habitation is established based on skeleton line network of blank region so that the matching object is transformed from habitation to skeleton line mesh. Secondly, the dual graph of skeleton line mesh is constructed by the connective topology, and the centrality indexes of each node in the dual graph can be calculated. Then the matching model of skeleton line mesh is established by polarization transformation and analytic hierarchy process, accordingly the matching results of skeleton line mesh can be obtained. Finally, the matching results of skeleton line mesh can be transformed into habitation matching results by the mapping relationship. The transformation of matching object, dual graph construction and polarization transformation of the skeleton line mesh can add the constraint conditions of topology and relative position to the matching process, so that the influence on matching caused by the obvious geometric position difference can be reduced significantly. Comparison experiments and analysis with other areal matching methods indicate that the proposed method can solve the matching problem among the areal habitation data of the large scale urban map with obvious geometric position difference effectively.

The Cross-media Publishing Data Model of Map

WEN Jianlong, YANG Chuncheng, FU Haojun, YUE Zhilan

2015, 44(8):  936-942.  doi:10.11947/j.AGCS.2015.20140304

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Aiming at the problem of repeated map production and differences of visual expression effect appeared when the same spatial data are published across different media, the concept of cross-media publishing of map is proposed. Through analyzing the existing map data models and deeply mining the potential advantages of PDF page content objects such as mark content object, logic structure object, optional content object and so on in PDF structure, the point is around the feature object code, the feature object structure and the feature layered structure launched the design of the cross-media publishing data model of map. The model breached the past limit that the map data which satisfies the printing request and geographic spatial data only can be described on different stages or with different models. It creates the conditions for storage and management of the cross-media publishing data of map. After the experimental tests the results show that the model is feasible and effective.

The Generalized Model and Parallel Computing Methods for Pixel-level Remote Sensing Image Fusion

YANG Jinghui

2015, 44(8):  943-943.  doi:10.11947/j.AGCS.2015.20150059

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Research on Photogrammetric Processing for Mars Topographic Mapping

GENG Xun

2015, 44(8):  944-944.  doi:10.11947/j.AGCS.2015.20150073

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