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20 September 2019, Volume 2 Issue 3
Resilient PNT Concept Frame
Yuanxi YANG
2019, 2(3):  1-7.  doi:10.11947/j.JGGS.2019.0301
Abstract ( 292 )   HTML ( 33)   PDF (789KB) ( 214 )  
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The concept of resilient positioning, navigation and timing (PNT) is described. The definition of resilient PNT is given, the relationship between integrated (or comprehensive) PNT and resilient PNT is analyzed, and it is pointed out that the integrated PNT is the foundation of resilient PNT. Resilient PNT should be divided into resilient sensor integration, resilient functional model and resilient stochastic model. The strategy and principles of resilient integration of sensors are discussed. The resilient integration of sensors should be designed following the optimal, available, compatible and interoperable principles. The concepts of resilient functional model and possible modification strategies of the different functional models are also described. Several possible optimal routes for resilient stochastic model improvements are also set forth. It is pointed out that the optimal improvements of stochastic models for multi PNT sources should follow the same variance scale. At last, the resilient PNT data fusion for state parameters are given based on the resilient functional and stochastic models.

Near-zone Direct and Indirect Topographic Effects Based on the Rectangular Prism and Surface Element
Jian MA,Ziqing WEI,Zhenghui YANG,Xiaogang LIU,Jianfeng JI
2019, 2(3):  8-17.  doi:10.11947/j.JGGS.2019.0302
Abstract ( 124 )   HTML ( 22)   PDF (350KB) ( 55 )  
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Helmert’s second method of condensation is an effective method for terrain reduction in the geoid and quasi-geoid determinations. Condensing the masses outside the geoid to a surface layer on the geoid produces several forms of topographic effects: direct effect on gravity, secondary indirect effect on gravity and indirect effects on the (quasi-) geoid, respectively. To strike a balance between computation accuracy and numerical efficiency, the global integration region of topographic effects is usually divided into near zone and far zone. We focus on the computation of near-zone topographic effects, which are functions of actual topographic masses and condensed masses. Since there have already been mature formulas for gravitational attraction and potential of actual topographic masses using rectangular prism model, we put forward surface element model for condensed masses. Afterwards, the formulas for near-zone direct and indirect effects are obtained easily by combining the rectangular prism model and surface element model. To overcome the planar approximation errors involved with the new formulas for near-zone topographic effects, the Earth’s curvature can be taken into account. It is recommended to apply the formulas based on the rectangular prism and surface element considering the Earth’s curvature to calculate near-zone topographic effects for high-accuracy demand to determine geoid and quasi-geoid.

The Precise Representation Model of Topological Relations of Complex Planar Objects
Zhanlong CHEN,Wen YE
2019, 2(3):  18-30.  doi:10.11947/j.JGGS.2019.0303
Abstract ( 109 )   HTML ( 11)   PDF (946KB) ( 70 )  
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For complex planar objects, which are composed of simple spatial objects, the existent models of topological relations may not be able to describe some topological attributes of complex objects well. Taking the topological content between complex objects into account, this paper presents a model of basic topological relations between line/planar objects, and then in which the basic topological relations and the concept of the overlapping area are leveraged to describe the topological relations of simple planar objects. The definition of traversing of the hole’s boundary and planar with a hole is used to describe the topological relations between complex planar objects. Finally, the five basic topological relationship description modes of complex planar objects are summarized to realize description of the details of topological relations between partitions of complex planar objects.

Object-oriented Battlefield Environment Simulation Process Object Model Based on Task-driven
Jie ZHU,Xiong YOU,Qing XIA,Hongjun ZHANG
2019, 2(3):  31-43.  doi:10.11947/j.JGGS.2019.0304
Abstract ( 150 )   HTML ( 9)   PDF (1060KB) ( 56 )  
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Battlefield environment simulation process is an important part of battlefield environment information support, which needs to be built around the task process. At present, the interoperability between battlefield environment simulation system and command and control system is still imperfect, and the traditional simulation data model cannot meet war fighters’ high-efficient and accurate understanding and analysis on battlefield environment’s information. Therefore, a kind of task-orientated battlefield environment simulation process model needs to be construed to effectively analyze the key information demands of the command and control system. The structured characteristics of tasks and simulation process are analyzed, and the simulation process concept model is constructed with the method of object-orientated. The data model and formal syntax of GeoBML are analyzed, and the logical model of simulation process is constructed with formal language. The object data structure of simulation process is defined and the object model of simulation process which maps tasks is constructed. In the end, the battlefield environment simulation platform modules are designed and applied based on this model, verifying that the model can effectively express the real-time dynamic correlation between battlefield environment simulation data and operational tasks.

Research and Evaluation on Key Technological Indicators for Airborne and Shipborne Gravimetry
Motao HUANG,Kailiang DENG,Taiqi WU,Xiuping LU,Guojun ZHAI,Yongzhong OUYANG,Xin CHEN,Min LIU
2019, 2(3):  44-54.  doi:10.11947/j.JGGS.2019.0305
Abstract ( 129 )   HTML ( 10)   PDF (380KB) ( 64 )  
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Gravimetry technical guides are the scientific basis for air-sea gravimetry. However, the existing technical guides in China are behind the application requirements. This study analyzed the most important indicators of air-sea gravimetry, including the density of survey lines, gravimetry accuracy and space resolution, stability and reliability of the air-sea gravimeter, and proposed a gravimetry accuracy assessment system consisting of gravity RMS of error, systematic error and mean error, and an assessment system for the gravimeter stability consisting of the relative accuracy of the scale value, monthly zero-drift, RMS of the monthly nonlinear zero-drift variation and the threshold of the monthly nonlinear zero-drift variation. The mathematic models for the measurement point determination in shipborne gravimetry, E?tv?s correction for airborne gravimetry, platform tilt correction and evaluation air-sea gravimetry were also analyzed and modified. This work will provide technology support for the composition of the military-civil air-sea gravimetry technical guides.

Hierarchical Area Partitioning Method of Urban Road Networks Matching
Bohua HUANG,Wei ZHONG,Renjian ZHAI,Qing ZHOU
2019, 2(3):  55-67.  doi:10.11947/j.JGGS.2019.0306
Abstract ( 145 )   HTML ( 18)   PDF (4693KB) ( 90 )  
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In view of the “Node-Arc” data model of road network in the aspect of structured expressing the deficiencies, the hierarchical area partitioning of road network based on the principle of stroke, which made road network space structure characteristics of the expression with the hierarchical feature was designed. Based on road hierarchy and connected relationship with the area domain boundaries, the road in the area was hierarchically divided. A hierarchical model was established based on “whole-part-object” data model. Finally, the model of urban road network matching is proposed, which used consistency evaluation model selected matching objects from high-grade road to the low-level road. The experiment results indicated that the method was suitable to solve the road matching problem with typical urban features.

Results and Analyses of BDS Precise Orbit Determination with the Enhancement of Fengyun-3C
Tian ZENG,Lifen SUI,Xiaolin JIA,Guofeng JI,Qinghua ZHANG
2019, 2(3):  68-78.  doi:10.11947/j.JGGS.2019.0307
Abstract ( 139 )   HTML ( 14)   PDF (953KB) ( 49 )  
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Global navigation satellite system occultation sounder (GNOS) Fengyun-3C was launched successfully on September 23, 2013, which carried GPS/BDS receiver for the first time. This provides the convenience to study the enhancement results of low earth orbiter satellite (LEO) to BDS precise orbit determination (POD). First the data characteristic and code observation noise of GNOS are analyzed. Then the enhancement experiments in the case of global and regional ground observation stations layout are processed with four POD schemes: BDS single system, GPS/BDS double system, BDS single system with GNOS observations, GPS/BDS double system with GNOS observations. The precision of BDS orbits and clocks are compared via overlapping arcs. Results show that in the case of global station layout the along directional precision of GEO satellite has the biggest improvement, with the improvement percentage 60%. Then the precision of cross direction and the along direction of remaining satellites shows the second biggest improvement. The orbit precision of BDS-only POD in part of observation arcs some satellite even suffers a slight decline. The root mean square (RMS) of overlapping clock difference of visible arcs in GPS/BDS POD experiments improves by 0.1ns level. As to the experiments of regional station layout with 7 ground stations, the orbit and clock overlapping precision and orbit predicting precision are analyzed. Results show that the predicting precision of BDS GEO satellites in the along direction improves by 85%. The remaining also has a substantial improvement, with the average percentage 21.7%. RMS of overlapping clock difference of visible arcs improves by 0.5ns level.

A Robust Gaussian Mixture Model for Mobile Robots’ Vision-based Pose Estimation
Chuanqi CHENG,Xiangyang HAO,Jiansheng LI,Peng HU,Xu ZHANG
2019, 2(3):  79-90.  doi:10.11947/j.JGGS.2019.0308
Abstract ( 142 )   HTML ( 9)   PDF (1790KB) ( 75 )  
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In dynamic environments, the moving landmarks can make the accuracy of traditional vision-based pose estimation worse or even failure. To solve this problem, a robust Gaussian mixture model for vision-based pose estimation is proposed. The motion index is added to the traditional graph-based vision-based pose estimation model to describe landmarks’ moving probability, transforming the classic Gaussian model to Gaussian mixture model, which can reduce the influence of moving landmarks for optimization results. To improve the algorithm’s robustness to noise, the covariance inflation model is employed in residual equations. The expectation maximization method for solving the Gaussian mixture problem is derived in detail, transforming the problem into classic iterative least square problem. Experimental results demonstrate that in dynamic environments, the proposed method outperforms the traditional method both in absolute accuracy and relative accuracy, while maintains high accuracy in static environments. The proposed method can effectively reduce the influence of the moving landmarks in dynamic environments, which is more suitable for the autonomous localization of mobile robots.