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概率时间地理是经典时间地理基于概率的一种扩展,它采用概率描述移动对象在可达位置的非等可能性。已有的概率时间地理是基于正态分布或布朗桥的,其方差与移动速度无关或随移动速度的增大而发散,因而难以兼顾应用针对性和稳定性。本文提出了一种基于马尔科夫链的概率时间地理方法。首先,构建中间关于两边的双向条件马尔科夫链,它在移动速度足够大时的极限可视为布朗桥,因而具有稳定性数字特征。然后,建立定向移动到马尔科夫链的映射关系,主要是根据定向移动的时空位置、移动速度等信息建立马尔科夫链的步长、状态空间和转移矩阵,这样马尔科夫链与移动速度有关。最后,利用双向马尔科夫链连续计算定向移动在任意时刻的概率分布云,其方差的针对性和稳定性在实例中进行了验证。 相似文献
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《武汉大学学报(信息科学版)》2016,(12)
结合我国北斗导航卫星系统的特点,通过对三频数据进行线性最优组合来有效探测和修复各类周跳。应用了5种线性几何无关组合并基于三步法进行周跳探测。对于探测到的不同周跳,通过特定的三频载波相位线性组合进行有效的分辨和修复,最后基于北斗三频实测数据,针对不同电离层延迟变化水平,分别就1s、15s、30s不同采样间隔下的周跳探测和修复能力进行了验证,取得了较优的结果。 相似文献
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北斗卫星导航系统基准站通常直接存储传输原始观测量,导致了两种不利情况：①没有形成对用户的分级授权机制,任意用户通过原始观测量都可以获取基准站的精确空间基准、时间基准和大气基准数据,这会对基准站的安全构成潜在威胁;②原始观测量之间的强相关性导致其数据量很大,在北斗接收机观测显现网络化、不间断、高采样和多波段的趋势下,观测数据的海量爆发给数据的存储和传输都带来了巨大的压力。因此,本文提出利用状态和残差来表达北斗基准站观测数据。与通用的基于RINEX、Compact RINEX和RTCM等国际协议的数据服务相比,其优点是不但可以对不同级别用户进行信息分级授权,从技术上保障数据服务的安全,而且大幅减小了存储传输数据量和用户端计算量。同时本文证明了新的表达方式与原始数据等效,不会降低最终计算结果的精度。利用该方法可以建立具有自主知识产权的北斗观测数据存储和传输协议,并为高精度星基数据播发服务提供技术支持。 相似文献
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共享自行车有效地解决了人们短距离出行的难题,但随着共享自行车的大量投放及使用,给城市管理带来了很大的挑战。文中基于高精度北斗卫星定位和电子围栏等技术,建立了共享自行车监管与服务平台,依托地面划定的停车区域,采用北斗高精度采集终端完成地面停车区域的多边形拐点坐标的采集,将采集后的坐标与电子地图结合形成虚拟的电子围栏,通过车辆的位置数据与电子围栏多个拐点组成的封闭区域进行对比匹配,进而判断是否在围栏内或围栏外停放车辆。对停入停放区的车辆进行数据统计,停放区外的车辆进行报警提示并实施处罚。实际应用中,该平台为解决共享自行车监管难题提出了一套完整的解决方案。 相似文献
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北斗数据质量分析软件设计与实现 总被引：1，自引：0，他引：1
随着北斗卫星导航系统的发展,北斗卫星数据在许多领域得到广泛应用,对北斗数据质量的监测变得越来越重要。文中在Visual Studio 2008开发平台下基于C++语言,设计并实现北斗数据质量分析软件,分析软件具有分析观测数据中多路径误差、周跳、载噪比、数据可用率和电离层延迟等信息的功能。利用开阔环境、树林环境、玻璃幕墙环境中的观测数据对分析软件进行测试,结果表明,分析软件能够真实反映出观测数据的质量情况。 相似文献
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采用Landsat TM数据分析了阿克苏河—塔里木河断面水质污染状况,通过波段的DN值和常规监测数据建立能反映水质状况的
污染物监测模型。结果发现,将2000年常规监测数据代入模型后,与遥感数据的结果基本吻合| 重建阿克苏河—塔里木河的连续水体
污染变化曲线,得出污染物浓度随着远离上游而增加。 相似文献
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Monitoring drought dynamics in the Aravalli region (India) using different indices based on ground and remote sensing data 总被引：5，自引：0，他引：5
C. Bhuiyan R.P. Singh F.N. Kogan 《International Journal of Applied Earth Observation and Geoinformation》2006,8(4):289-302
The hard-rock hilly Aravalli terrain of Rajasthan province of India suffers with frequent drought due to poor and delayed monsoon, abnormally high summer-temperature and insufficient water resources. In the present study, detailed analysis of meteorological and hydrological data of the Aravalli region has been carried out for the years 1984–2003. Standardised Precipitation Index (SPI) has been used to quantify the precipitation deficit. Standardised Water-Level Index (SWI) has been developed to assess ground-water recharge-deficit. Vegetative drought indices like Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) and Vegetation Health Index (VHI) have been computed using NDVI values obtained from Global Vegetation Index (GVI) and thermal channel data of NOAA AVHRR satellite. Detailed analyses of spatial and temporal drought dynamics during monsoon and non-monsoon seasons have been carried out through drought index maps generated in Geographic Information Systems (GIS) environment. Analysis and interpretation of these maps reveal that negative SPI anomalies not always correspond to drought. In the Aravalli region, aquifer-stress shifts its position time to time, and in certain pockets it is more frequent. In comparison to hydrological stress, vegetative stress in the Aravalli region is found to be slower to begin but quicker to withdraw. 相似文献
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Piyoosh Rautela Ramesh Chandra Lakhera 《International Journal of Applied Earth Observation and Geoinformation》2000,2(3-4)
The area around Sataun in the Sirmur district of Himachal Pradesh, India (falling between the rivers Giri and Tons; both tributaries of the Yamuna River) was studied for landslide vulnerability on behalf of the inhabitants. The study was made using extensive remote sensing data (satellite and airborne). It is well supported by field evidence, demographic and infrastructural details and aided by Geographic Information System (GIS) based techniques. Field observations testify that slope, aspect, geology, tectonic planes, drainage, and land use all influence landslides in the region. These parameters were taken into consideration using the statistical approach of landslide hazard zonation. Using the census data of 1991, vulnerability of the populace to the landslide hazard was accessed. As most of the infrastructure in the region is concentrated around population centres, population data alone was used for vulnerability studies. 相似文献
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ZHAN F. Benjamin 《地球空间信息科学学报》2011,(1)
Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2000, 200... 相似文献
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GNSS系统及其技术的发展研究 总被引：3，自引：1，他引：2
阐述了国际上卫星导航系统的总体发展,对美、俄、欧、中的四大全球系统,以及相关的区域系统和增强系统进行了简单的介绍,研究分析了GNSS系统及其技术的发展趋势,同时分析了我国Compass全球系统面临的机遇和挑战,并提出了我国未来工作的建议. 相似文献
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自动车辆定位导航系统中传感器的误差分析 总被引：1，自引：0，他引：1
对国界定位导航系统中几种常见的辅助传感器所产生的误差进行了分析，导出了不同传感器的误差模型。这些误差模型是估计车辆位置的扩展卡尔曼滤波器的基础，同时也为选择适当的传感器提供了理论根据。 相似文献
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“4D”技术及其应用 总被引：13，自引：0，他引：13
介绍“４Ｄ”（即数字地面模型、数字正射影像、数字栅格地图和数字线划地图）系列产品的生产流程、关键技术、及其在耕地保护、防灾减灾救灾和城市规划等方面的应用方法。 相似文献
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《International Journal of Digital Earth》2013,6(1):66-87
Abstract Virtual Australia is not a well-defined or agreed concept. This discussion paper conceptualises Virtual Australia as a ‘virtual [digital] model containing and representing all non-trivial objects and their contextual environment – from blue sky to bedrock – in real world Australia’. It describes a scenario for Virtual Australia, one or two decades from now, in which the locations and conditions of non-trivial objects and their environment are updated automatically through a combination of remote sensing and wireless communication technologies in support of a ‘Supranet’. It then examines the concept of the ‘Supranet’ – a pervasive information network based largely on wireless technology linking the physical world to a virtual model in real time – and develops and discusses three principal characteristics of the Supranet: the ability to have or collect specific information (know); the ability to process information (think); and the ability to communicate that information. If, in the near future, any or all non-trivial devices are to some extent able to know, think and communicate, the potential for object autonomy will be realised. 相似文献