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      • GPS-based monitoring and modeling of the ionosphere and its applications for high accuracy correction in China

        Yuan Yunbin,Ou Jikun,Huo Xingliang,Wen Debao,Liu Genyou,Chai Yanji,Yang Renggui,Luo Xiaowen 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-

        The main research conducted previously on GPS ionosphere in China is first introduced. Besides, the current investigations include as follows: (1) GPS-based spatial environmental, especially the ionosphere, monitoring, modeling and analysis, including ground/space-based GPS ionosphere electron density (IED) through occultation/ tomography technologies with GPS data from global/regional network, development of a GNSS-based platform for imaging ionosphere and atmosphere (GPFIIA), and preliminary test results through performing the first 3D imaging for the IED over China, (2) The atmospheric and ionospheric modeling for GPS-based surveying, navigation and orbit determination, involving high precisely ionospheric TEC modeling for phase-based long/ median range network RTK system for achieving CM-level real time positioning, next generation GNSS broadcast ionospheric time-delay algorithm required for higher correction accuracy, and orbit determination for Low-Earth-orbiter satellites using single frequency GPS receivers, and (3) Research products in applications for national significant projects: GPS-based ionospheric effects modeling for precise positioning and orbit determination applied to China’s manned space-engineering, including spatial robot navigation and control and international space station intersection and docking required for related national significant projects.

      • Effect of Light Intensity on Close-Range Photographic Imaging Quality and Measurement Precision

        Kaifeng Ma,Ximin Cui,Guiping Huang,Debao Yuan 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.2

        To test the effectiveness of flash intensity in digital close-range photogrammetry, test methods for the light intensity adjustment of a ring-flash on close-range photographic imaging quality and measuring precision were researched respectively. First, according to the efficiency of the flash, the imaging characteristics, and the gray distribution of the mark points of the image, the identified method of the image gray value for subjective visual analysis was presented, and a quality standard for the close-range photographic image was provided. Then, as a precondition to obtaining the best image quality, based on the estimation theory governing measurement adjustment precision, the changes in measuring precision under conditions of different light intensity and different photographic distances were analysed, and the relationships between measurement precision and light intensity, or photographic distance, were obtained. Finally, the globally optimal imaging quality and measurement precision for any given light intensity were quantified. Experimental results indicated that the root mean square (RMS) errors of the measurement adjustment precision were 0.028 mm, 0.039 mm, and 0.085 mm: the RMS errors in the measuring precision and the corresponding coordinate repeatability were 0.038 mm, 0.053 mm, and 0.118 mm. The best imaging quality was achieved at photographic distances of 3 m, 5 m, and 7 m, with corresponding output light intensities of 1/64, 1/32, and 1/16 under certain conditions, respectively. This can satisfy the precision requirements for large-scale coordinate measurement, and provides a basis for formulating a reasonable light intensity output from a ring-flash in the digital close-range photogrammetry.

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