Seabed photographing has been applied with various underwater camera apparatuses(UCAs)for observations of megabenthic epifauna,which reveals more details than traditional sampling tools do.In this study,we improved a ...Seabed photographing has been applied with various underwater camera apparatuses(UCAs)for observations of megabenthic epifauna,which reveals more details than traditional sampling tools do.In this study,we improved a UCA named a towed underwater video-camera system(TUV system)with image processing software for seabed photographing in coastal areas up to 100 m.In May 2017,the TUV system was tested at 4 stations in the Zhangzi Island marine area in the northern Yellow Sea to investigate local megabenthic epifauna,especially brittle stars.At each station,more than 500 good seabed photographs each in area of 0.1550 m2 were obtained in just 10 min.Almost all of the epifauna larger than 1 mm could be identified from the photographs,including echinoderms,bivalves,cnidarians,and crustaceans.Three dominant brittle stars(Ophiopholis mirabilis,Ophiura sarsii vadicola,and Stegophiura sladeni)were spotted,and their abundance,disc diameter,cluster size,and coverage area were calculated and analyzed from the seabed photographs.The results show that the TUV system could be applied in coastal waters of hard sandy bottoms and could be used for quantitative investigations of megabenthic epifauna.展开更多
This paper proposes a novel self-calibration method for a large-FoV(Field-of-View)camera using a real star image.First,based on the classic equisolid-angle projection model and polynomial distortion model,the inclinat...This paper proposes a novel self-calibration method for a large-FoV(Field-of-View)camera using a real star image.First,based on the classic equisolid-angle projection model and polynomial distortion model,the inclination of the optical axis is thoroughly considered with respect to the image plane,and a rigorous imaging model including 8 unknown intrinsic parameters is built.Second,the basic calibration equation based on star vector observations is presented.Third,the partial derivative expressions of all 11 camera parameters for linearizing the calibration equation are deduced in detail,and an iterative solution using the least squares method is given.Furtherly,simulation experiment is designed,results of which shows the new model has a better performance than the old model.At last,three experiments were conducted at night in central China and 671 valid star images were collected.The results indicate that the new method obtains a mean magnitude of reprojection error of 0.251 pixels at a 120°FoV,which improves the calibration accuracy by 38.6%compared with the old calibration model(not considering the inclination of the optical axis).When the FoV drops below 20°,the mean magnitude of the reprojection error decreases to 0.15 pixels for both the new model and the old model.Since stars instead of manual control points are used,the new method can realize self-calibration,which might be significant for the long-duration navigation of vehicles in some unfamiliar or extreme environments,such as those of Mars or Earth’s moon.展开更多
参照GPS精密单点定位(PPP,Precise Point Positioning)模型设计了一种新的卫星定轨方法-组合星载加速度计测量数据和IGS提供的GPS精密星历及精密钟差数据进行低轨卫星的精密定轨。利用星载加速度计提高卫星受力模型准确性,使动力法定轨...参照GPS精密单点定位(PPP,Precise Point Positioning)模型设计了一种新的卫星定轨方法-组合星载加速度计测量数据和IGS提供的GPS精密星历及精密钟差数据进行低轨卫星的精密定轨。利用星载加速度计提高卫星受力模型准确性,使动力法定轨精度和可靠性都得到提升。同时,采用多种改正技术提高GPS非差观测值测量精度,保证最终高精度卫星定轨。本文建立了卫星定轨的轨道滤波模型,得出了有益的结论,即采用星载加速度计测量卫星非保守力可提高卫星定轨精度,在ITRF2000参考系下三轴精度优于18cm。这种方法不需要在全球建立基准观测站,定轨设备简单,费用低廉。展开更多
超大型天文观测技术的出现不仅能够让研究人员观测到新的天文现象,更能用于验证已有物理模型的正确性.这些最新天文成果的发现是建立在海量天文数据的近乎实时产生、管理与分析的基础上,因此给目前的数据管理系统带来了新的挑战.以我国...超大型天文观测技术的出现不仅能够让研究人员观测到新的天文现象,更能用于验证已有物理模型的正确性.这些最新天文成果的发现是建立在海量天文数据的近乎实时产生、管理与分析的基础上,因此给目前的数据管理系统带来了新的挑战.以我国自主研发的地基广角相机阵(the ground-based wide-angle camera array,GWAC)天文望远镜为例,15s的采样和处理周期都处于短时标观测领域的世界前列,但却对数据管理系统提出了很多问题,包括多镜头并行输出数据管理、实时瞬变源发现、当前观测夜数据的秒级查询、数据持久化和快速离线查询等.基于上述问题,设计了分布式GWAC数据模拟生成器用于模拟真实GWAC数据产生场景,并基于产生的数据特性,提出一种两级缓存架构,使用本地内存解决多镜头并行输出、实时瞬变源发现,使用分布式共享内存实现秒级查询.为了平衡持久化和查询效率,设计一种星表簇结构将整个星表数据划分后聚集存储.根据天文需求特点,设计基于索引表的查询引擎能从缓存和星表簇以较小的代价对星表数据查询.通过实验验证,当前方案能够满足GWAC的需求.展开更多
基金Supported by the Key Program for International S&T Cooperation Projects:Sino-Australian Center for Healthy Coasts(No.2016YFE0101500)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDA23050501,XDA19060201)the Taishan Scholars Project to SUN Song。
文摘Seabed photographing has been applied with various underwater camera apparatuses(UCAs)for observations of megabenthic epifauna,which reveals more details than traditional sampling tools do.In this study,we improved a UCA named a towed underwater video-camera system(TUV system)with image processing software for seabed photographing in coastal areas up to 100 m.In May 2017,the TUV system was tested at 4 stations in the Zhangzi Island marine area in the northern Yellow Sea to investigate local megabenthic epifauna,especially brittle stars.At each station,more than 500 good seabed photographs each in area of 0.1550 m2 were obtained in just 10 min.Almost all of the epifauna larger than 1 mm could be identified from the photographs,including echinoderms,bivalves,cnidarians,and crustaceans.Three dominant brittle stars(Ophiopholis mirabilis,Ophiura sarsii vadicola,and Stegophiura sladeni)were spotted,and their abundance,disc diameter,cluster size,and coverage area were calculated and analyzed from the seabed photographs.The results show that the TUV system could be applied in coastal waters of hard sandy bottoms and could be used for quantitative investigations of megabenthic epifauna.
基金co-supported by the National Natural Science Foundation of China(Nos.42074013 and 41704006)。
文摘This paper proposes a novel self-calibration method for a large-FoV(Field-of-View)camera using a real star image.First,based on the classic equisolid-angle projection model and polynomial distortion model,the inclination of the optical axis is thoroughly considered with respect to the image plane,and a rigorous imaging model including 8 unknown intrinsic parameters is built.Second,the basic calibration equation based on star vector observations is presented.Third,the partial derivative expressions of all 11 camera parameters for linearizing the calibration equation are deduced in detail,and an iterative solution using the least squares method is given.Furtherly,simulation experiment is designed,results of which shows the new model has a better performance than the old model.At last,three experiments were conducted at night in central China and 671 valid star images were collected.The results indicate that the new method obtains a mean magnitude of reprojection error of 0.251 pixels at a 120°FoV,which improves the calibration accuracy by 38.6%compared with the old calibration model(not considering the inclination of the optical axis).When the FoV drops below 20°,the mean magnitude of the reprojection error decreases to 0.15 pixels for both the new model and the old model.Since stars instead of manual control points are used,the new method can realize self-calibration,which might be significant for the long-duration navigation of vehicles in some unfamiliar or extreme environments,such as those of Mars or Earth’s moon.
文摘参照GPS精密单点定位(PPP,Precise Point Positioning)模型设计了一种新的卫星定轨方法-组合星载加速度计测量数据和IGS提供的GPS精密星历及精密钟差数据进行低轨卫星的精密定轨。利用星载加速度计提高卫星受力模型准确性,使动力法定轨精度和可靠性都得到提升。同时,采用多种改正技术提高GPS非差观测值测量精度,保证最终高精度卫星定轨。本文建立了卫星定轨的轨道滤波模型,得出了有益的结论,即采用星载加速度计测量卫星非保守力可提高卫星定轨精度,在ITRF2000参考系下三轴精度优于18cm。这种方法不需要在全球建立基准观测站,定轨设备简单,费用低廉。
文摘超大型天文观测技术的出现不仅能够让研究人员观测到新的天文现象,更能用于验证已有物理模型的正确性.这些最新天文成果的发现是建立在海量天文数据的近乎实时产生、管理与分析的基础上,因此给目前的数据管理系统带来了新的挑战.以我国自主研发的地基广角相机阵(the ground-based wide-angle camera array,GWAC)天文望远镜为例,15s的采样和处理周期都处于短时标观测领域的世界前列,但却对数据管理系统提出了很多问题,包括多镜头并行输出数据管理、实时瞬变源发现、当前观测夜数据的秒级查询、数据持久化和快速离线查询等.基于上述问题,设计了分布式GWAC数据模拟生成器用于模拟真实GWAC数据产生场景,并基于产生的数据特性,提出一种两级缓存架构,使用本地内存解决多镜头并行输出、实时瞬变源发现,使用分布式共享内存实现秒级查询.为了平衡持久化和查询效率,设计一种星表簇结构将整个星表数据划分后聚集存储.根据天文需求特点,设计基于索引表的查询引擎能从缓存和星表簇以较小的代价对星表数据查询.通过实验验证,当前方案能够满足GWAC的需求.
