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Table of Content

    20 February 2014, Volume 43 Issue 2
    Satellite Formation for a New Gravity Field Exploration Mission
    2014, 43(2):  111-117. 
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    Short-term TEC Prediction of Ionosphere Based on ARIMA Model
    2014, 43(2):  118-124. 
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    Abstract: With a fully consideration of the Multiplicative Seasonal model, we transform a seasonal time series for ionspheric Total Electron Content (TEC) into a stationary time series by seasonal differences and regular differences firstly, then use Autoregressive Integrated Moving Average (ARIMA) model from the time series analysis theory to model the stationary TEC values so as to predict the TEC series. Using the TEC data from 2008 to 2012 provided by the Center for Orbit Determination in Europe (CODE) as sample data, we analysed the precision of this method in the prediction of ionosphere TEC value which varies from high latitude to low latitude in both quiet and active period. The effect of TEC sample’s length on the predicted accuracy is analyzed, too. Results from numerical experiments show that in ionospheric quiet period the average relative prediction accuracy of 6 days are up to 83.3% with an average prediction residual errors of about 0.18±1.9TECu, while it changes to 86.6% with an average prediction residual errors of about 0.69±2.6TECu in ionospheric active period. For the former, above 90% of predicted residual is less than ±3TECu while the latter is only about 81%. Two periods show the same law that the higher the latitude, the higher the absolute precision, and the lower the predicted relative accuracy. In addition, the prediction accuracy will improve with the increase of TEC sample sequences length, but it will gradually reduce if the length exceed the optimal length about 40 days. On the other hand, with the same TEC sample, the predicted days increase, the predicted accuracy decreases. Though it’s not obvious in the beginning, it will be significantly reduced over 30 days.

    A Simplification of The Meridian Formula and Its Taylor-series Interpretation
    2014, 43(2):  125-130. 
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    A more concise formula of the meridian arc length was obtained by introduced two new parameters: the third flattening and the Gauss hypergeometric function. From another perspective, the simplified formula is also can be explained by a Taylor series expansion. By this, we got error estimate of the formula in terms of the Lagrange form of the remainder. For numerical verification of the error estimate theory, application example was presented by using the WGS84 data. The results show that experimental data are consistent with the error estimate theory and the simplified formula is more precise than the standard one.

    Kinematic Single Epoch Positioning Algorithm Based on Wide-Lane Combination and Track Constraints
    2014, 43(2):  131-136. 
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    A key issue of kinematic single epoch positioning is the correct resolution of ambiguity. We can improve the reliability of the single epoch ambiguity resolution by adding constraints. When the receiver moves along a road center line, we can calculate the approximate mileage by pseudorange differential positioning, then construct track constraints according to line design data of the mileage. Wide lane Ambiguity can be determined relatively easily because its wavelength is longer. Firstly, wide lane ambiguity is fixed by additional track constraints damped LAMBDA,then ambiguities of L1 and L2 are determined through additional track constraints again. Experimental results show that the proposed algorithm has a high resolution success rate.

    Motheds of Equipement Delay Estimation Using Pseudorange, Carrier Phase and Inter-Satellite Ranging Observations
    2014, 43(2):  137-142. 
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    Navigation signal equipment group delay is assimilated into satellite clock corrections broadcasted in the navigation message. Considering the necessity to keep consistent with GNSS user algorithms for positioning and timing, it’s pointed out that the satellite clock offsets solved with inter-satellite ranging observations should also include the group delay of navigation payload onboard GNSS satellites. It was found that equipment delays of crosslink devices appear in observation equation in the form of combination with the group delay of navigation payloads: the sum of receiving equipment delay and the group delay forms combined receiving delay, while transmitting equipment delay subtracting the group delay forms combined transmitting delay. We made many efforts to discuss the method for dealing with the problem of equipment delay and two approaches were proposed: one is to estimate the combined transmitting and receiving delay parameters for each satellite, another is to estimate the delay bias (the sum of combined transmitting delay and combined receiving delay) parameters for each pair of directed linked satellites. Software for simulation and data processing has been developed and the feasibility of the proposed method and data processing strategy were validated by simulation analysis. The result indicates that. by implementation of both the two proposed approach, the accuracy of orbit and clock result would be significantly improved and the effect is nearly the same as if the combined delays have been exactly corrected.

    A SAR change detection method based on polarimetric distance measure
    2014, 43(2):  143-150. 
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    A new distance measure derived from the polarimetric coherency matrix was proposed on the basis of classical Wishart distance originally developed for polarimetric SAR image classification. A change detection methodology based on the proposed polarimetric distance measure was then developed. An experiment of change detection using two RADARSAT-2 quad-polarized images acquired in 2009 and 2010 respectively over a suburb area of Beijing was carried out. The change detection capability of the polarimetric distance measure was compared to the log-ratio images formed by the radar intensities of different polarization channels and the total scattered power (the Span). The results showed that the polarimetric distance measure could highlight all types of land cover changes, while only part of change types were visible on intensity-related log-ration images. Moreover, the difference image generated from the polarimetric distance presented highest separability between changed and unchanged pixels. Therefore, the proposed change detection method could be widely applicable for change detection from polarized SAR images.

    SAR Image Modeling Based on the Mixture Gamma Heavy-tailed Rayleigh Distribution
    2014, 43(2):  151-157. 
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    Aimed at normal resolution SAR image can't model accurately for the high resolution SAR image,this paper proposes an efficient statistical model, called mixture Gamma heavy-tailed Rayleigh distribution specially for high resolution SAR image. In this model,we model the speckle using the Heavy-tailed Rayleigh density to describe the characteristic of sharp peak and heavy tail of the high resolution SAR image. And we model the RCS by introducing the mixture Gamma density to characterize the complex fluctuation characteristics of the high resolution SAR. Based on the Mellin transformation,we derive mixture Gamma heavy Rayleigh distribution log- cumulant Parameter estimation formula to improve the accuracy of parameter estimation, therefore, to achieve accurate modeling of the high resolution SAR image. Furthermore, experimental results on several actual SAR images are given and we compare our method with some existing methods. Experimental results demonstrate that the modeling proposed in this paper can model for various high resolution SAR images,and it has higher fitting accuracy.

    AN IMAGE FUSION METHOD BASED ON SPECTRUM PROJECTION AND WAVELET TRANSFORMING WITH HYPERSPECTRAL AND MULTISPECTRAL IMAGES
    2014, 43(2):  158-163. 
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    When the hyperspectral and multispectral images are fused, the spectral information of the fused image changed a lot because the spatial resolution is improved and the situation of the mixed pixels is weakened. The pixels change should be considered to solve this shortage. In view of this situation, the multispectral image is used to simulate a hyperspectral image using the method of projection and the wavelet transformation (WT) is used to fuse the simulated and original hyperspectral images. The fused image can not only enhance the spatial information, but also correct the spectral information, and thus can increase the application accuracies such as the environmental abnormal detection. The Hyperion image and the SPOT-5 image are chosen to do the experiment of fusion, 87.2 percent of the target areas can be distinguished when making use of the fused image.

    Unsupervised urban detection from High-Resolution Remote-Sensing Imagery based on Improved Harris corner detector
    2014, 43(2):  164-169. 
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    Traditional urban detection methods are mainly based on global image feature, such as texture, spectrum and shape etc. However, these features are not invariant to scale and illumination changes, which consequently reduce the robust of the existing algorithms. To solve this problem, we propose the use of local feature for urban detection from high-resolution remote-sensing imagery. The proposed method consists of three steps: First, we extract a large set of local feature point by Harris corner detector. In order to achieve a reliable extraction of corners from urban areas, we further propose two criterions to validate and filter them. Afterwards, we incorporate the extracted corners into a likelihood function, and use it to measure the possibility of each pixel belonging to the urban area. Finally, we extract urban area by an adaptive binary segmentation method. Experimental results show that the proposed approach outperforms the existing algorithms in terms of detection accuracy.

    A method for automatic identification of the foot point of slope based on D-P algorithm
    2014, 43(2):  170-177. 
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    The foot point of slope is the core limits of the continental shelf beyond 200 nautical miles. According to the 76th article in United Nations Convention on the Law of the Sea (brief in UNCLOS) and related technical requirements of the Commission on the Limits of the Continental Shelf, we discussed the method and technical process for the identification of the foot point of slope. In this paper, a quadratic simplified method based on the D-P algorithm and extreme points of second derivation was proposed by analyzing the terrain, slope, second derivation and the D-P profile synthetically. A quadratic derivative method was advanced also based on original and D-P profile. The original profile was simplified in 7 procedures and multiple decision methods were given such as the slope, depth, second derivation to the data, concavity, continuity and segmentation to the profile in order to identify the foot point of slope automatically. The underlying program was developed and result was coincided with the international commercial software for outer limits determination. The effectivity of the method had been verified by applying it to the real multibeam bathymetric data.

    Experimental Research on Optimization of DEM Interpolation Parameters
    2014, 43(2):  178-192. 
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    Interpolation parameter is one of the basic elements of the DEM interpolation method. Different interpolation parameters produce different interpolation precisions and, the differences may be huge by using various interpolation parameters. But for ordinary users, it is difficult to select an appropriate set of interpolation parameters during the interpolation process. In the related researches on interpolation method, using the appropriate interpolation algorithm or interpolation parameters may lead to potentially serious consequences, even completely opposite experimental conclusions. Therefore, based on the difference of the weight determination method in interpolation algorithm, this paper selected related parameters with inverse distance weighted interpolation method, radial basis functions interpolation method and ordinary kridging interpolation method, and focused on selecting "Optimized" interpolation parameters in interpolation method. First according to the different effects of the interpolation parameters on interpolation accuracy, took the relevant interpolation parameters as the experimental object. Then chosen six different regions of landform types of the sparse distribution and discrete sampling data as data source, and applied a series of methods such as cross validation, correlation analysis, trend surface analysis and variance of analysis to systematic research on choosing optimized DEM interpolation parameters and proposed the uncertainty of the interpolation parameters of the "optimum" value range.

    An algorithm for determining the touching and crossing relations between a pair of lines based on one line splitting plane to two parts
    2014, 43(2):  186-192. 
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    Touching and crossing are two important refined intersection types in the line/ line topological relations. They usually play important roles in spatial dada modeling, quality control, and updating. In order to overcome the limitations of determining the refinement cases, i.e., touching and crossing in the current literatures, a new algorithm is presented in this paper. This algorithm is based on the foundation that a line splits the neighborhood into two parts. If we can determine the other line is located on only one part or on the two sides, we can distinguish the refined cases of intersections. The algorithm has been developed using Visual C#, and have made good application effect in GIS database updating system.

    Research of Geo Semantic Spatial Index and Query Based on GeoQuad
    2014, 43(2):  193-199. 
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    In order to quickly and efficiently query Geo Semantic data, by analyzing the lack of traditional RDF Index and Spatial Index method, this paper proposes a construction method of Geo Semantic Spatial Index based on GeoQuad, and realizes the Geo SPARQL Spatial Query by this method based on Jena and ARQ. Experiments show that this method is feasible and efficient, It is not only able to locate the spatial RDF nodes quickly, and can quickly spatial query Geo RDF data, returning RDF results.

    Triangulation network intersection algorithm based on conformal geometric algebra
    2014, 43(2):  200-207. 
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    Traditional triangular mesh intersection calculation methods are insufficient in complex logical structures and not unified in dimensions. To overcome these disadvantages, an adaptive algorithm, based on the geometric algebra, is proposed in this paper. It is founded on the meet operator and from the unified object expression and relation computation perspectives. The outer product expression in Conformal Geometric Algebra, which has a property of Grassmann structure consistency, is used for constructing the geometric algebra expression of the triangular mesh. The triangular intersection algorithm is constructed based on the meet operator. The object and dimensional adaptive characteristics of this algorithm is discussed. Finally, case studies based on the Antarctic ice sheet simulation data are proposed to verify the algorithm. The result suggests the proposed algorithm can well support the complex triangle mesh intersection operations, and simplify the algorithm structures and enhance the multidimensional applicability. Our research can provide a reference for the multi-dimensional unified spatial analysis methods based on geometric algebra.

    Improved Map Matching Algorithm Based on D-S Evidence Theory
    2014, 43(2):  208-220. 
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    The map matching algorithm based on D-S evidence theory of vehicle-borne navigation system often uses position and angle evidences in map matching algorithm, but with the increasingly complex structure of the transport network in the city, this algorithm results have some limitations and the matching accuracy can not meet the need of vehicle networking technology. With the continuous development of GPS and other positioning equipment, the data of vehicle speed and positioning interval can be obtained accurately. On this basis, this article put reachability evidence as the third evidence fusion with the integration result of the first two evidence. What’s more, by simulation training for different road network topology, we obtained more accurate position and angle reliability parameters for practical application. Results of simulation show that this map matching algorithm dramatic increase in accuracy and stability, especial suited for complex road network in cities.

    Symbolic Expressions of Difference Extrema Between Regular Latitudes
    Shaofeng Bian
    2014, 43(2):  214-220. 
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    Systematic comparisons of six regular latitudes in geodesy and cartography were carried out. Symbolic expressions of difference extreme points with corresponding extrema between these six regular latitudes were derived and expressed in a power series of eccentricityby computer algebra system. Taking CGCS2000 reference ellipsoid for example, differences between regular latitudes were shown through numerical values. The results show that difference extreme points between auxiliary and geodetic latitudes are all at the right side of. Difference extremum between geocentric and geodetic latitudes is the largest, while the one between reduced and geodetic latitudes is the smallest. The findings could provide theoretical basis for geodetic surveying and map projection.