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卫星授时技术控制方案
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作者 梁双有 《陕西天文台台刊》 CSCD 1995年第6期48-50,共3页
根据我国同步广播卫星的现状,本文提出在不专门占用卫星信道的情况下,保留现有的CCTV中的时间信号,并将卫星轨道参数以及其它参数插入到CCTV信号中去的技术问题以及控制方法,完成同步卫星的高精度授时工作。
关键词 同步卫星 授时技术 通信卫星 卫星仪道
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Automatic Road Extraction in Rural Areas Based on Digital Imaging and Laser Scanner Data
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作者 Claudionor Ribeiro da Silva Jorge Ant6nio Silva Centeno Maria Joao Henriques 《Journal of Civil Engineering and Architecture》 2011年第4期285-296,共12页
Digitizing road maps manually is an expensive and time-consuming task. Several methods that intend to develop fully or semi-automated systems have been proposed. In this work we introduce a method, based on the Radon ... Digitizing road maps manually is an expensive and time-consuming task. Several methods that intend to develop fully or semi-automated systems have been proposed. In this work we introduce a method, based on the Radon transform and optimal algorithms, which extracts automatically roads on images of rural areas, images that were acquired by digital cameras and airborne laser scanners. The proposed method detects linear segments iteratively and starting from this it generates the centerlines of the roads. The method is based on an objective function which depends on three parameters related to the correlation between the cross-sections, spectral similarity and directions of the segments. Different tests were performed using aerial photos, Ikonos images and laser scanner data of an area located in the state of Parana (Brazil) and their results are presented and discussed. The quality of the detection of the roads centerlines was computed using several indexes - completeness, correctness and RMS. The values obtained reveal the good performance of the proposed methodology. 展开更多
关键词 Radon transform automatic extraction ROADS laser scanning digital image
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