基于北斗卫星导航系统的飞行物轨迹标记法     

申莹  王樱子  王辉  王智森 《测绘科学》2015,40(2):26-28,87

为了实时准确地掌握和了解导航系统飞行物的位置和空间关系,以提高北斗系统的运行准确性,该文根据北斗卫星导航系统不间断授时服务特点,提出一种利用北斗卫星授时信号估计空间飞行物轨迹的方法。卫星下发的授时信号到达用户终端的过程中,受到空间飞行物的遮挡而产生扰动。用户终端将接收的扰动信号的变化量通过各种网络汇聚到数据中心,如果用户终端、空间星座和地面数据中心的时钟同步,在多个用户终端存在的条件下,将数据中心计算出的飞行物的时空参量等信息标注到空间地理信息系统上,连接这些空间点,就可以绘制出空间飞行物的运动轨迹。  相似文献   

Visualizing spatiotemporal trajectories of mobile social media users using space–time cube     

Chen Xu  Han Qin  Manzhu Yu 《制图学和地理信息科学》2015,42(4):75-83

The implementation of social network applications on mobile platforms has significantly elevated the activity of mobile social networking. Mobile social networking offers a channel for recording an individual’s spatiotemporal behaviors when location-detecting capabilities of devices are enabled. It also facilitates the study of time geography on an individual level, which has previously suffered from a scarcity of georeferenced movement data. In this paper, we report on the use of georeferenced tweets to display and analyze the spatiotemporal patterns of daily user trajectories. For georeferenced tweets having both location information in longitude and latitude values and recorded creation time, we apply a space–time cube approach for visualization. Compared to the traditional methodologies for time geography studies such as the travel diary-based approach, the analytics using social media data present challenges broadly associated with those of Big Data, including the characteristics of high velocity, large volume, and heterogeneity. For this study, a batch processing system has been developed for extracting spatiotemporal information from each tweet and then creating trajectories of each individual mobile Twitter user. Using social media data in time geographic research has the benefits of study area flexibility, continuous observation and non-involvement with contributors. For example, during every 30-minute cycle, we collected tweets created by about 50,000 Twitter users living in a geographic region covering New York City to Washington, DC. Each tweet can indicate the exact location of its creator when the tweet was posted. Thus, the linked tweets show a Twitter users’ movement trajectory in space and time. This study explores using data intensive computing for processing Twitter data to generate spatiotemporal information that can recreate the space–time trajectories of their creators.  相似文献   

齐平3井钻井施工技术          下载免费PDF全文

孟祥波 《探矿工程》2015,42(8):22-24

齐平3井是部署在松辽盆地中央坳陷区齐家凹陷的一口水平探井,完钻斜深3574.03 m,垂深2201.1 m,水平段长1195.35 m。在施工前对井身结构和井眼轨迹剖面进行了优化设计,施工中应用井眼轨迹控制技术、地质导向技术,并配以钻井安全施工工艺,保证了该井的顺利完钻,实现了设计要求的各项技术指标,取得了良好的施工效果。  相似文献   

Integration of nighttime light remote sensing images and taxi GPS tracking data for population surface enhancement     

Bailang Yu  Ting Lian  Yixiu Huang  Xinyue Ye  Zuoqi Chen 《International journal of geographical information science》2019,33(4):687-706

The population distribution grid at fine scales better reflects the distribution of residents and plays an important role in investigating urban systems. The recent years have witnessed a growing trend of applying the nighttime light data to the estimation of population at micro levels. However, using the nighttime light data alone to estimate population may cause the overestimation problem due to excessively high light radiance in specific types of areas such as commercial zones and transportation hubs. In dealing with this issue, this study used taxi trajectory data that delineate people’s movements, and explored the utility of integrating the nighttime light and taxi trajectory data in the estimation of population in Shanghai at the spatial resolution of 500 m. First, the initial population distribution grid was generated based on the NPP-VIIRS nighttime light data. Then, a calibration grid was created with taxi trajectory data, whereby the initial population grid was optimized. The accuracy of the resultant population grid was assessed by comparing it with the refined survey data. The result indicates that the final population distribution grid performed better than the initial population grid, which reflects the effectiveness of the proposed calibration process.  相似文献   

移动轨迹的尺度特征     

刘民士  龙毅  孙勇 《测绘通报》2020,(4):134-138

移动轨迹是移动对象在地理空间环境中移动而留下的痕迹。移动轨迹数据是一类特殊的地理时空数据，它具有时间尺度、空间尺度和语义尺度特征。本文首先分析了轨迹数据的空间尺度特征与时间尺度特征，建立了轨迹空间尺度与时间尺度转换关系式；然后论述了轨迹的语义内涵和语义尺度特征，将轨迹语义分为移动对象语义、地理空间环境语义、采集设备语义、移动方式语义，并从地理空间环境语义的角度分析了轨迹的语义多尺度；最后探讨了轨迹语义尺度与时空尺度之间的一致性关系。  相似文献   

Clinoforms and clinothems: Fundamental elements of basin infill     

Claudio Pellegrini  Stefano Patruno  William Helland-Hansen  Ronald J. Steel  Fabio Trincardi 《Basin Research》2020,32(2):187-205

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A Cascade Approach for Global Trajectory Tracking Control of Underactuated AUVs     

毕凤阳  魏英杰  张嘉钟  曹伟 《中国海洋工程》2010,24(2):369-380

A global trajectory tracking controller is presented for underactuated AUVs with only surge force and yaw moment in the horizontal plane. A transformation is introduced to represent the tracking error system into a cascade form. The global and uniform asymptotic stabilization problem of the resulting cascade system is reduced to the stabilization problem of two subsystems by use of the cascade approach. For the stabilization of the subsystem involving the yaw moment, a control law is proposed based on the feedback linearization method. Another subsystem is stabilized by designing a fuzzy sliding mode controller which can offer a systematical means of constructing a set of shrinking-span and dilating-span membership functions. In order to demonstrate the practicability of the proposed controller, control constraints, parameter uncertainties, and external disturbances are considered according to practical situation of AUVs. Simulation results show very good tracking performance and robustness of the proposed control schemes.  相似文献   

Evolution of high-Mg–Al granulites from Sunkarametta, Eastern Ghats, India: evidence for a lower crustal heating–cooling trajectory     

Bose    Fukuoka    Sengupta  & Dasgupta 《Journal of Metamorphic Geology》2000,18(3):223-240.

A suite of high-Mg–Al granulites from Sunkarametta, Eastern Ghats Belt, India, shows contrasting prograde assemblages of extremely aluminous orthopyroxene+cordierite+sapphirine and similarly aluminous orthopyroxene+Ti-rich spinel in closely associated domains. Textural and compositional characteristics indicate that both were derived from prograde dehydration–melting of biotite–plagioclase–quartz-bearing protoliths. The former assemblage was stabilized at relatively more magnesian bulk composition. Geothermobarometric data and petrogenetic grid considerations place 'peak' metamorphic conditions at c. 950 °C and 9 kbar. Subsequent to peak metamorphism, the rocks cooled to c . 700–750 °C, with slight lowering of pressure, and the retrograde reactions also involved melt–solid interaction. The inferred P – T  trajectory is one of heating–cooling at lower crustal (25–30 km) depths.  相似文献   

贵州安顺市PM2.5气象输送条件及贡献源空间分布     

曹青  谷晓平  张翅鹏  陈贞宏  吴哲红 《气象与环境学报》2022,38(2):55-61

利用贵州省安顺市2015—2019年大气污染物资料和气象资料,分析安顺市空气质量特征和主要大气污染物特征,通过TrajStat软件中HYSPLIT模型的后向轨迹模式,结合GDAS气象数据、PM_2.5浓度,分析不同季节输送途径及其污染轨迹,采用潜在源贡献作用和浓度权重轨迹分析方法,分析研究期内所有PM_2.5污染日（PM_2.5日浓度高于75 μg·m^-3）输送轨迹垂直与水平方向分布特征。结果表明: PM_2.5是安顺城区主要大气污染物,冬季输送污染轨迹占比较大,输送方向主要为贵州东北方向、偏南方向; 污染日PM_2.5输送路径以贵州东北方向近距离输送为主,该类轨迹基本分布在880—980 hPa高度; 潜在源高值区主要集中在贵阳整个地区、毕节织金县、黔西市、金沙县等,高贡献值区主要集中在安顺紫云县、镇宁县、毕节织金县、大方县等。  相似文献   

一次爆发性气旋引发东北地区暴雨成因分析     

王宁  马梁臣  霍也 《气象与环境学报》2022,38(3):19-28

利用2016年5月2—4日NCEP的FNL 1°×1°再分析资料和GDAS的1°×1°再分析资料、地面观测资料,运用天气学分析、等熵位涡、物理量诊断和水汽来源追踪等方法,从大尺度环流背景、水汽源地和输送、动力和热力机制、等熵位涡等方面对2016年春季一次地面气旋爆发性发展导致的东北地区暴雨天气过程进行了分析。结果表明:位于40°N附近的黄淮气旋北上加强发展,2日14时至3日14时中心气压下降24 hPa,超过爆发性气旋的定义标准。500 hPa高空槽快速加强发展为闭合低涡,低空切变线加强发展为低空低涡,其东部形成明显的低空急流,为暴雨区提供水汽和热量,为东北地区典型的暖式切变降水。等熵位涡自320 K高层向305 K低层输送下传,并逐步向南向东移动,高空正位涡的下传促使地面气旋快速发展,上升运动加强,有利于暴雨的出现。比湿在6 g·kg^(-1)以上对东北地区春末夏初暴雨预报有一定的参考意义。水汽主要来源于东海、黄海及西北太平洋。暴雨区与850 hPa水汽通量散度的负值区、700 hPa垂直速度和850 hPa绝对涡度大值区较为一致,强降水区与850 hPa相当位温密集带和暖区锋生区相对应,降水位于能量锋区以及偏暖区一侧。  相似文献