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Acta Geodaetica et Cartographica Sinica 2010 Vol.39 Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select A New Calibration Algorithm of Interferometric Parameters for Dual-antenna Airborne InSAR Systems Acta Geodaetica et Cartographica Sinica    Abstract （2275）      PDF（pc） （1361KB）（1605）       Knowledge map    Save It is significant to calibrate interferometric parameters of dual-antenna airborne InSAR（Interferometric Synthetic Aperture Radar）systems for deriving accurate DEM (Digital Elevation Model) with large areas. A new outside calibration model considering phase offset, baseline length and baseline angle was proposed in order to calibrate interferometric parameters effectively, which was induced from the basic theory of DEM deriving from InSAR. And its solution scheme was designed. The outside calibration experiments were done with height control points measured by GPS to calibrate the dual-antenna airborne InSAR system researched independently by Institute of Electronics, Chinese Academy of Sciences. The accuracy of heights derived with calibrated interferometric parameters was calculated, as validated the proposed calibration model and its solution algorithm. Related Articles | Metrics Select A New InSAR Phase Unwrapping Method Based on Local Frequency Estimation and Multigrid Technique LIU Zi-Long ,Bin Cai,Zhen Dong Acta Geodaetica et Cartographica Sinica    Abstract （1479）      PDF（pc） （1405KB）（1695）       Knowledge map    Save A new phase unwrapping method based on local frequency estimation and multigrid technique is proposed. In this algorithm, the phase difference is replaced by local frequency estimation. Firstly, a coarse unwrapped phase was obtained with FFT, and then the fine unwrapped phase is achieved with multigrid technique. The weighting parameters are set according to the confidence of local frequency estimation. The method needs no extra phase filtering process, so the processing module is simplified and the processing time is reduced. It is proved by experiments that our method can largely improve the accuracy of InSAR. Related Articles | Metrics Select Combined Bundle Block Adjustment Based on Existing Ground Control Points and Multi-period Aerial Imageries Acta Geodaetica et Cartographica Sinica    Abstract （1740）      PDF（pc） （976KB）（1624）       Knowledge map    Save In order to make the best of existing aerial imageries and ground control points，save cost and reduce working hours，a new method of combined bundle block adjustment based on existing ground control points and multi-period aerial imageries is put forward in the paper. Firstly, the mathematical model of combined bundle block adjustment is deduced. Then the data sets of a place in the south of China are used to validate the proposed method. The experiment results show that the combined bundle block adjustment can deliver the effect of existing ground control points from former aerial imageries to later aerial imageries through the corresponding points among them. The plane accuracy of pass points of the combined bundle block adjustment is similar to that of the conventional bundle block adjustment. The height accuracy of pass points is dependent on the observation number of corresponding points among the multi-period aerial imageries. The more the observations of corresponding points are, the better the height accuracy of pass points is. So as long as there are enough observations of corresponding points among the multi-period aerial imageries in the same area, the accuracy of pass points derived from combined bundle block adjustment will be meet the topographic maps specifications for aerophotogrammetric operation. Related Articles | Metrics Select Modeling of Ionosphere VTEC using Generalized Regression Neural Network Acta Geodaetica et Cartographica Sinica    Abstract （1154）      PDF（pc） （1017KB）（1432）       Knowledge map    Save Abstract: This paper presents a new idea to model ionosphere vertical total electron content based on generalized regression neural network. Firstly, coefficients of network model, including input coefficients, smooth coefficients and sampling strategy of training data, are determined according to time and space characteristic of vertical total electron content. Then, we have discussed how sampling strategy influences network model performance in time and space field respectively. Finally, the feasibility and availability of network model are proved by investigation scenario, the accuracy of network model in ample data region can reach 90%, and which is about 83% in the blank data region. Related Articles | Metrics Select A NEW SAR SUPERRESOLUTION ALGORITHM BASED ON APODIZATION EXTRAPOLATION Acta Geodaetica et Cartographica Sinica    Abstract （1213）      PDF（pc） （1435KB）（1377）       Knowledge map    Save The paper develops a new technique enhancing SAR resolution as well as suppressing sidelobes based on apodization technique. The method make use of the expand effect of signal bandwidth after apodization, and use an inverse weight function to equalize the SVA spectrum. A modified noninteger Nyquist SVA formulation is used to suppress sidelobes after extrapolation. Examples and quantity analysis demonstrate the effectiveness of the paper’s method. Related Articles | Metrics Select The GPS/INS Integrated Positioning And Orientation In The Aerial Remote Sensing Based On The High-Order INS Stochastic Error Model SUN Hong-Xing Acta Geodaetica et Cartographica Sinica    Abstract （1343）      PDF（pc） （1249KB）（1566）       Knowledge map    Save Direct Georeferencing (DG), also referred to as direct platform orientation (DPO), is defined as direct measurement of the imaging sensor external orientation parameters (EOP), using positioning and orientation sensors of the Global Positioning System (GPS) and Inertial Navigation System (INS). Imaging sensors, most frequently supported by the DPO technique, include digital cameras, lidar systems, multi-spectral or hyper-spectral scanners, interferometric synthetic aperture radar (INSAR), and etc. With direct sensor orientation, the requirement for ground control, tie-point matching and aerotriangulation (AT) is significantly reduced, or even entirely eliminated, resulting in shorter times of data acquisition and processing, and streamlined and highly automated data workflow and quality control. Despite significant progress in GSP/INS-based direct georeferencing technology in the last decade, there is still room for improvement in terms of better accuracy. The main objective of this paper is the stochastic modeling of Inertial Measurement Unit (IMU) errors, which determines significantly the final performance of the GPS/INS integrated system. With the random constants, random walks and first-order Markov process models to characterize the stochastic errors of IMU, one Kalman Filter with 36 states was meticulously established. The practical data was processed with the filter in the experiment and the accuracies in term of standard deviations of 5cm in position, 0.002 degree in attitude and 0.008 degree in heading were achieved respectively. Related Articles | Metrics Select Polygon Overlay Analysis Algorithm Based on Monotone Chain and STR Tree in the Simple Feature Mode Acta Geodaetica et Cartographica Sinica    Abstract （1451）      PDF（pc） （1431KB）（1496）       Knowledge map    Save This paper introduces an improved algorithm for Overlay Analysis based on monotone chain and STR(Sort-Tile-Recursive) tree index. Based on the monotone chain, this algorithm reduces the times that the vertex lists are traversed and consumed times of computing intersection point, so less memory space and running time are required. Make full use of the character of overlay analysis of the simple feature, this algorithm as many leaves as possible are filled to capacity in the STR tree index structure to reduce the access times when query the polygons in the spatial database. This algorithm split the Edges in the polygon by the monotone chain algorithm to compute the intersect point firstly. Secondly, the concept of plane graph is used in this algorithm. This algorithm organizes the result polygons by computing the topology location between the plane graph component and the two polygons. This paper has reduced the computing intersect point time and emphasizes on the solution of the problem of the entry point or exit-point successive and the repeated points, and the alternative searching of the intersected polygon. Performance tests show this algorithm is more efficient and quicker than the algorithm based on the topological model and the other algorithms especially when the data quantity goes to large. Related Articles | Metrics Select Parallel Image Matching Algorithm Based on GPGPU Acta Geodaetica et Cartographica Sinica    Abstract （1273）      PDF（pc） （1208KB）（1808）       Knowledge map    Save With the development of satellite remote sensing technology, it is the key issue in remote sensing field to transform massive data into user information in short time. The traditional image matching algorithms for optimization and implementation which were designed for common processor CPU, could not be effectively applied on Graphics Processing Unit (GPU). A fast image matching parallel algorithm is presented based on General-Purpose computing on Graphics Processing Units (GPGPU) which support Compute Unified Device Architecture (CUDA). The algorithm can execute high performance parallel computing in Single Instruction Multiple Thread (SIMT) Pattern. On the basis of the parallel architecture and hardware characteristic of GPU, the parallel algorithm introduces three speedup methods to improve the implementation performance: execution configuration technology, high-speed storage technology and global storage technology optimizes the data storage structure and improves the data access efficiency. The experiment result shows that GPU can with high efficiency implement the parallel algorithm and processing efficiency of 8-bit 1280×1024 pictures can be up to the highest Multiprocessor Warp Occupancy, processing speed is 7 times faster than CPU-based implementation. The comparison between CUDA and CPU in image matching algorithms shows the advance of the CUDA in high arithmetic intensity real-time processing and computing data processing and this provides new methods and ideas to optimize image matching performance and GPGPU. Related Articles | Metrics Select A Vector-based Indirect Method for Seamless Occlusion Detection in True Orthophoto Generation 1,Xianfeng Huang 2 Acta Geodaetica et Cartographica Sinica    Abstract （1276）      PDF（pc） （1495KB）（1373）       Knowledge map    Save Z-buffer is the dominate method for occlusion detection, but it’s just effective in a utopian situation that terrain is smooth and the ground resolution of DSM is the same as arial images, ortherwise false occlusion and false visibility will be introduced .This paper analyses the artefacts generated by Z-buffer and its advanced algorithms in true ortho-image generation, and proposes a novel vector-based inderect method (VIM) to avoid algorithm-introduced artefacts. The proposed method projects the vetor polygons to image space, then judges polygon cover priority for pixels covered by more than one polygons, from which the visibility of DSM grids can be deduced. At last a filter algorithm is developed to eliminate artefacts between polygons caused by calculation errors and rounding error. Experiments prove that, with the VIM method, occlusion detection is a simple ,seamless and robust process, and can avoid all artefacts in the orthophotos. Related Articles | Metrics Select Study of Satellite level 2A Image Rigorous Model and Orientation Algorithms Acta Geodaetica et Cartographica Sinica    Abstract （1196）      PDF（pc） （1019KB）（1329）       Knowledge map    Save This paper proposes concept of rigorous mathematics model for 2 image of the linear pushroom satellite for the first time, and constructs a rigorous mathematics model by deriving direct and inverse transformation of 2 image. Based on this model, we have studied on the feasibility of using RPC model of 2 image to replace this rigorous mathematics model, which is on the purpose of simplifying the model of 2 image and speeding up the operating speed as well. And then, in the fourth part in this paper, the RPC model is used as the orientation model, instead of the traditional orientation model. In the experimental verification part of this paper, we use SPOT5 HRG images as experimental data to prove the feasibility and effectiveness of above proposed and designed model for 2 image of the linear pushroom satellite. The experimental results show that proposed 2 image rigorous mathematics model is rigorous. Besides its RPC model could be used to orient 2 image, and the orientation accuracy of 2 image rigorous mathematics model is no lower than that of 1 image. Furthermore, this paper provides an innovative theoretical and experimental basis for the definition of image product levels. Related Articles | Metrics Select Acta Geodaetica et Cartographica Sinica    Abstract （1350）      PDF（pc） （552KB）（3893）       Knowledge map    Save Related Articles | Metrics Select Geo-positioning Research based on High-Resolution Satellite Stereo Imagery for Metropolitan Areas Acta Geodaetica et Cartographica Sinica    Abstract （978）      PDF（pc） （1265KB）（1549）       Knowledge map    Save Related Articles | Metrics Select Design and development for updating national 1:50,000 topographic databases in China Acta Geodaetica et Cartographica Sinica    Abstract （1065）      PDF（pc） （693KB）（1560）       Knowledge map    Save The currency of geographic data refers to its consistency with respect to the real world, and plays a critical role in geographic information service and applications. In order to improve the quality of geographic information service, State Bureau of Surveying and Mapping of China had launched a five year’s national campaign to update 1:50,000 topographic database. This paper outlines the technical design and development of this national updating engineering, which adopts a full coverage updating strategy characterized by all element topographic data modeling, change detection in all related areas, and whole process data quality controlling. High resolution image-based updating and large-scale data generalization-based updating were developed and used as two majors updating techniques. A technical system for massive updating production has been developed and equipped to a large number of production units. Related Articles | Metrics Select Acta Geodaetica et Cartographica Sinica    Abstract （802）      PDF（pc） （1515KB）（1781）       Knowledge map    Save Related Articles | Metrics Select The Tectonic stress variation derived by using GPS data before Wenchuan Ms=8.0 strong earthquake Zhang Yongzhi Acta Geodaetica et Cartographica Sinica    Abstract （1216）      PDF（pc） （972KB）（1249）       Knowledge map    Save Abstract WenChuan Ms=8.0 strong earthquake which occurred on 12 May 2008, killed and hurt about forty thousand of people， damaged much property due to stress release and faults slip in LongMenshan region. Based on Green’s second interior integration, the formulas to calculate interior stress variation from displacement velocity on earth surface is derived in this paper. The computed methods are discussed and analyzed. In the last, the maximum principal stress and shear in depth 15 Km of the earth crust is computed by using GPS displacement velocity data observed from 2001 to 2005 in SiChuan region. The results show that the compressional principal stress variation is largest near the epicenter and the shear variation is not obvious. Related Articles | Metrics Select The Research on the Analysis Methods of Residential Land Supplying Based on Real Estate Market Information System ---- taking Shanghai as a case Acta Geodaetica et Cartographica Sinica    Abstract （804）      PDF（pc） （1262KB）（1237）       Knowledge map    Save Related Articles | Metrics Select Algorithm for constructing Voronoi Diagram of function radiation area based on the road networks analysis Acta Geodaetica et Cartographica Sinica    Abstract （1207）      PDF（pc） （1528KB）（1394）       Knowledge map    Save An algorithm for constructing Voronoi diagram and Weighted-Voronoi diagram of radiation area of function centers based on network analysis was proposed in this paper. Because road network system plays an important role in the conduction of central influences and functions, Voronoi diagram and Weighted-Voronoi diagram of radiation area constructed by analyzing network shortest path and network shortest path pass time can delineate factually the practical situation of spatial partition for different central influences, which can be used to support forcefully spatial analysis and spatial optimization. The processes of adjacent road analysis and region discretization, searches and generation for adjacent node to function centers, network Voronoi diagram partition based on Dijistra algorithm and computation for demarcation nodes, generation of Voronoi diagram of radiation area and vectorization were mainly discussed in this paper. The computational experiment shows that the proposed algorithm is of rational design and reliable and efficient performance, which can simulate Voronoi diagrams of radiation area with expectant precision and complicate modality, and has flexibility and practical value. Related Articles | Metrics Select Hierarchical Urban Building Extraction from High-Resolution Remote-Sensing Imagery Based on Object-Oriented Acta Geodaetica et Cartographica Sinica    Abstract （1366）      PDF（pc） （1344KB）（1892）       Knowledge map    Save An automatic urban building extraction method for high-resolution remote-sensing imagery, which combines building segmentation based on neighbor total variations with object-oriented analysis, is presented in this paper. Aimed at different extraction complexity from various buildings in the segmented image, a hierarchical building extraction strategy with multi-feature fusion is adopted. Firstly, we extract some rectangle buildings which remain intact after segmentation through shape analysis. Secondly, in order to ensure each candidate building target to be independent, multidirectional morphological road-filtering algorithm is designed which can separate buildings from the neighboring roads with similar spectrum. Finally, we take the extracted buildings and the excluded non-buildings as samples to establish probability model respectively, and Bayesian discriminating classifier is used for making judgment of the other candidate building objects to get the ultimate extraction result. The experimental results show that the approach is able to detect buildings with different structure and spectral features in the same image. The results of performance evaluation also support the robustness and precision of the approach developed. Related Articles | Metrics Select Study on Urban Large-scale True Orthophoto Generation Wenhan Xie 2 Acta Geodaetica et Cartographica Sinica    Abstract （1373）      PDF（pc） （1412KB）（1682）       Knowledge map    Save When applying the traditional orthorectification methods to generate urban large-scale orthophoto, there exist many problems, for example, the spatial objects of orthophoto in urban areas are distorted from their true positions. This distortion shows that buildings lean over a street. Recent years, some researcher addressed the concept of true orthophoto. This paper mainly discusses the problem of shadow and occlusion, and presents key methods of true orthophoto generation. In order to orthorectify a building to its correct, upright position, the building must be represented as part of the surface to be rectified. Although the DSM can represent the building surface, the orthophoto generated using the DSM cannot achieve satisfactory accuracy. Therefore, an exact digital building model, which describes the building structure, three-dimensional coordinates, topologic relationship, etc., is required. The basic steps of true orthophoto generation must include DBM-based orthophoto generation. With the CSG building model, this paper addresses DBM-based occlusion and shadow detection for true orthophoto generation. A test field located in downtown of Denver, Colorado has been used to test our methods. The experimental results demonstrated that the proposed method in this paper can effectively solve the problem mentioned above. Related Articles | Metrics Select A quantitative analysis of urban growth and associated thermal characteristics using remote sensing data Acta Geodaetica et Cartographica Sinica    Abstract （1346）      PDF（pc） （1430KB）（1488）       Knowledge map    Save Urbanization transforms the natural landscape to anthropogenic urban land use and changes surface physical characteristics. Accurate information on the extent of urban growth and its impacts on environment are of great interest for diverse purposes. As a result, increased research interest is being directed to the mapping and monitoring of urban land use using remote sensing techniques. However, there are many challenges in deriving urban extent and development densities quantitatively. This study utilized remote sensing data of Landsat TM/ETM+ to assess urban sprawl and its thermal characteristics in Changsha of central China. A new approach was proposed for quantitatively determining urban land use extents and development densities. Firstly, impervious surface areas were mapped by integrating spectral index derived from remotely sensed data. Then, the urban land extents and development densities were identified by using moving window calculation and selecting certain threshold values. The urban surface thermal patterns were investigated using Landsat thermal band. Analysis results suggest that urban extent and development density and surface thermal characteristics and patterns can be identified through qualitatively based remotely sensed index and land surface temperature. Results show the built-up area and urban development densities have increased significantly in Changsha city since 1990s. The differences of urban development densities correspond to thermal effects where higher percent imperviousness is usually associated with higher surface temperature. Remotely sensed index and land surface temperature are demonstrated to be very useful sources in quantifying urban land use extent, development intensity, and urban thermal patterns. Related Articles | Metrics Select Maximum Likelihood Estimation in Mixed Integer Linear Model with P-Norm Distribution , Acta Geodaetica et Cartographica Sinica    Abstract （2889）      PDF（pc） （971KB）（2138）       Knowledge map    Save The integer parameters must be primarily estimated in the GNSS and INSAR application, which essentially introduces a special mixed integer model with both real- and integer-valued parameters from mathematical point of view. Up to now, all methods for mixed integer model are based on the least squares criterion. In this paper, the parameter estimation will be investigated in mixed integer model with the P-norm distributed observation noises. First of all, we will employ the maximum likelihood estimation theory to derive the criterion for integer searching, considering the fact that only real parameters can be differentiated but not the integer parameters due to their discrete property, and further verify that least squares based integer searching criterion is just a case with normally distributed noises. Secondly, the approach and iterative procedure are given for estimating p, searching integers and solving real-valued parameters. Finally, the simulated experiments are implemented to verify the correctness of the derived formulae and proposed algorithm. Related Articles | Metrics Select Acta Geodaetica et Cartographica Sinica    Abstract （958）      PDF（pc） （1038KB）（1803）       Knowledge map    Save Related Articles | Metrics Select Symbolic Expressions of the Track Calculation Methods Based on the Ellipsoidal Model Acta Geodaetica et Cartographica Sinica    Abstract （1104）      PDF（pc） （1050KB）（1540）       Knowledge map    Save The deficiencies of the traditional track calculation methods are analyzed in this paper. In order to improve the accuracy of track calculation, the symbolic formulae of meridian arc’s forward and inverse solution are introduced, then the modified Mercator sailing method is derived based on the ellipsoidal model. The calculation formula of middle latitude is derived from its geometrical definition based on an elliptical earth, and the modified middle latitude sailing method is also available. The two methods derived by this paper are both symbolic expressions, so they could solve the problem of accurate track calculation when different referenced ellipsoids are used, and thereby provide a theoretical model for the development of accurate automatic navigation. Related Articles | Metrics Select The Construction of Newly Stable Celestial Reference System QIAO ShuboQIAO ShuboLI Jin-Ling 2,LI Jin-Ling 2, 3, 3, 3, 3, 3, 3 Acta Geodaetica et Cartographica Sinica    Abstract （1353）      PDF（pc） （879KB）（1280）       Knowledge map    Save When we descript the motion of spherical bodies and some geophysical phenomena, we need one high precision and steady celestial reference system(CRS). Ideal celestial reference system equate to an inertia reference system, we call them basic celestial reference system. Celestial reference frame(CRF) is the realization of ideal CRS, which stability directly determined the precision of motion of objects and some geophysical phenomena. Based on nearly 30 years astrometric/geodetic observed data of global IVS（International VLBI Service）net between 1979 to 2007, we calculated and analyzed the data using CALC_Solve software system on Shanghai Astronomical Observatory, Chinese Academy of Sciences. Then we acquired a series coordinates(right ascension and declination) of radio sources, which can be made up to time series for our research. Stability of sources are checked and analyzed by the time series, we worked out a set of standard of selection on stable sources, and then we acquired a set of table of stable sources. At last we realized a newly stable celestial reference system consist of 173 stable defining sources and 135 supplement sources, which padded the blank of not renewing ICRF(International Celestial Reference Frame) for more than 10 years. The newly CRF can provide highly precision reference frame for some problems correlation on geodesy, astrometry and geophysics research. Related Articles | Metrics Select A Map Matching Algorithm for GPS Tracking Data Acta Geodaetica et Cartographica Sinica    Abstract （2620）      PDF（pc） （1350KB）（2289）       Knowledge map    Save Map matching GPS floating car tracking data is different from that for traditional navigation system according to the specific application. With the consideration that GPS floating car tracking data provide a global moving trend, using drive constraints in city road networks, this paper proposed a novel map matching method based on road connectivity under geometric topology and traffic control constraints as well as the similarity between the curve of trajectory and the outline of road paths. This algorithm can get good map matching results and was validated through experiments, and finally could support the further analysis and application of GPS floating car data. Related Articles | Metrics Select Evaluating on precision index of Vehicle-borne urban information acquisition and 3D modeling system 2, 2, 2, 2 Acta Geodaetica et Cartographica Sinica    Abstract （1451）      PDF（pc） （1311KB）（1538）       Knowledge map    Save The error sources and rigorous deducing of Vehicle-borne urban information acquisition and 3D modeling system (3DSurs) is analyzed on theory in this paper, and we analyze and evaluate the theorical precision, and get the precision index of 3Dsurs system. The error of 3Dsurs system includes error from GPS receiver antenna positioning, vehicle-borne attitude measurement, coordinate transformation, and scanner calibration and so on, it is shows that the plane precision is up to 10cm and the height precision is about 20cm of from theory analysis and large numbers of experiments. Related Articles | Metrics Select Creating Class Intervals for Choroplethic Maps Based on Multiobjective Genetic Algorithm 2, 2 Acta Geodaetica et Cartographica Sinica    Abstract （1350）      PDF（pc） （1441KB）（1927）       Knowledge map    Save Creating class intervals for choroplethic maps is a common and traditional subject in cartography, which is widely applied in many fields. The core of the problem is how to specify the class intervals. However, this work has focused almost exclusively on grouping the nearby distributed data into several ordinal bins along the number line. All enumerated units that fall into each bin are then assigned an areal symbol that is used to create the choroplethic map. The geographical characteristics of the data are only indirectly considered by such approaches in classification. In this article, we design, implement, and evaluate a new approach in classification that places class-interval selection into a multi-criterion framework. In this framework, we consider not only number–line relationships, but also the area covered by each class, the fragmentation of the resulting classifications, and the degree to which they are spatially autocorrelated. This task is accomplished through the use of a genetic algorithm (SIM-MOGA) that creates optimal classifications with respect to multiple criteria. Finally, the method has been tested in the urban land grading of Huibei Province. Related Articles | Metrics Select Unsupervised Two-Threshold Change Detection Algorithm Based on Wavelet Transform in Multi-temporal SAR Images Acta Geodaetica et Cartographica Sinica    Abstract （1368）      PDF（pc） （1333KB）（1791）       Knowledge map    Save The difficulty of multi-temporal synthetic aperture radar (SAR) image change detection is that SAR coherence imaging mechanism is very complex and it brings speckle noise. Wavelet multi-scale decomposition can reach the balance effect for the reduction of SAR image speckle noise and the protection of geometry detail, furthermore, it can describe SAR image changes through different scales. This paper proposes the unsupervised two-threshold wavelet transform (UTWT) SAR image change detection algorithm. Using the expectation maximization (EM) algorithm produces two threshold values, which can distinguish change classes (the enhanced change region and the weakened change region) or change grades. Finally, some SAR images perform experiments and the experimental results verify that the method is effective. Related Articles | Metrics Select Global sea level variations from combined Jason-1 and GRACE data Acta Geodaetica et Cartographica Sinica    Abstract （1317）      PDF（pc） （994KB）（1636）       Knowledge map    Save Sea level variations are mostly caused by ocean mass variations and steric sea level variations. Seasonal variability of global mean sea level and its two components from September 2002 to April 2008 is investigated respectively from combined GRACE time variable gravity and Jason-1 satellite altimeter data. Mean sea level change from combined satellite observations is quite consistent with WOA05 results at annual amplitudes and phases. The secular trend of global mean sea level change and its two components is estimated, during over 6.5 year`s time scale, global mean sea level rises at a rate of +2.0±0.4 mm/a, the respective contribution of ocean mass sea level and steric sea level is estimated to be +1.4±0.4 mm/a and +0.5±0.3 mm/a. Related Articles | Metrics Select study on Block Adjustment for Long-Strip satellite CCD Images Acta Geodaetica et Cartographica Sinica    Abstract （1418）      PDF（pc） （1171KB）（1868）       Knowledge map    Save The orientation model of space borne images based on orbit parameters and that based on state vectors are compared in this paper. A method for the fitting of orbit and the interpolation of state vectors based on imprecise ephemeris data is proposed and the orbit correction model that is suitable for long-strip satellite image orientation is built in flight coordinate system. Then, the influence of rotation of the Earth to the rigorous orientation model of satellite linear array images is analyzed. Through adaptive process of the yaw angle, imaging equation and block adjustment model of spaceborne linear array images are built based on satellite state vectors in Earth Centered Rotating coordinate system. At last, 4 pairs (8 scenes) SPOT5/HRS long-strip stereo images in Eastern Tibet Plateau and Eastern Talimu Basin from Project of China Western Topographic Mapping at 1:50,000 scale are used as data sources. According to different numbers and distributions of GCPs, positioning experiments of different schemes are carried out. Experiment results show that the statistical precision can achieve 8.0 m under the circumstance of sparse GCPs. Related Articles | Metrics