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《武汉大学学报(信息科学版)》2016,(12)
介绍了一种基于内接正八面体和Snyder投影的近似等积格网构建方法。先构建与球面面积相等的正八面体,将正八面体的面作为初始剖分面,然后采用四元三角剖分方法将初始剖分面分割成层次嵌套的三角格网,利用Snyder等积投影将正八面体面上的层次格网投影至球面,用大圆弧代替Snyder投影弧,构建近似等积的全球离散格网系统。在分析Snyder投影弧和大圆弧差异的基础上,依次计算各层次格网的面积、长度、角度值;根据计算结果分析了不同层次近似等积格网面积、长度、角度变形规律及空间分布特征。结果表明,随着剖分层次的增加,格网面积误差呈减小的趋势;剖分层次为10时,99.8%的格网面积偏差在-10%~10%之间,面积变形较大的格网均位于由正八面体面的中心到三个顶点的连线附近;格网长度、角度最大值与最小值的比均呈收敛的趋势,分别收敛至1.73和3.03。 相似文献
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球面菱形格网因其几何结构简单、方向一致、径向对称等特性,在空间操作和数据集成方面有着广泛的应用。本文基于“纬线环法”构建了球面四元三角剖分模型,分析了该方法带来的格网单元面积变形及其位置分布,发现该模型的三角单元面积变形具有“锯齿状”分布特征,即相邻的上下两个格网单元总是一大一小交替分布,而且变形方向一致。据此通过合并上下两个相邻三角形格网单元,构建了一种近似等面积的菱形剖分模型。结果表明,相比较于其他球面菱形格网生成方法,该方法计算简单、格网单元方向一致(长轴沿南北向分布);同时,格网单元的面积变形更小、分布更加均匀。 相似文献
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在分析当前球面空间数据结构的基础上,讨论了利用Snyder等积投影在二十面体上建立球面空间基础剖分方式的思路,然后在初始投影面上采用六边形格网进行层次细分,获得多分辨率的全球铺盖。提出了基于六边形格网的三叶节点管理与瓦片编码的基本思路,确立了球面不同实体的六边形格网表达模式。在此基础上,提出了基于球面六边形铺盖的Voronoi图生成算法,实验验证了算法的正确性与效率。 相似文献
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椭球面在球面上描写的探讨和应用 总被引:1,自引:0,他引:1
本文对椭球面在球面上的描写,作了进一步的探讨,发现并证明了三个特点:1.不论变形条件是等角的、等距离的或等面积的,其投影常数除积分常量外,都是相同的。2.不论变形条件如何,纬线上的投影长度比在一定宽度的纬度带内可视为一致。3.在一定宽度的纬度带内,按上述三种变形条件导出的投影公式分别算得的同一点的球面纬度和球面经差,几乎完全相等。根据上述的论点,在实用上可以按不同的精度要求,算出纬度带的宽度,该带内对双重投影法中两次描写的变形条件必须一致的规定,可以不予考虑,以便利用球面作为计算的过渡站来简化椭球面上或地(海)图上某些复杂计算。并着重探讨了用于海图方面的纬度带宽度,提出了在一定宽度的纬度带内,大地距离可看作球面距离,大地方位角可看作球面方位角的论点以及把海图的墨卡托投影改正为球面墨卡托投影,以便将球面上的计算结果不经反描写的换算就能直接记入海图的论点,为海图上加绘各种等值线提供了有利条件。最后提出了本法则应用于高斯-克吕格投影及其换带的计算、不同投影坐标之间的直接换算以及海图上加绘双曲线格网等实例。 相似文献
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随着云计算、航天遥感、地理信息、导航等技术的发展,用于空间信息剖分组织的全球多分辨率离散格网模型得到了长足发展。针对已有研究成果和当前研究现状,选取性能优异的六边形作为基本格网单元,Fuller多面体投影作为投影类型,提出了一种基于正八面体构建新型六边形球面离散格网的方法。全文系统地论述了此新型离散格网的生成算法并给出了相应实验结果,最后与基于Snyder等积多面体投影的格网进行比较,得出其特点和应用前景。 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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“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
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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