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991.
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针对地理空间数据交换和共享平台的地名数据日益增多及不同部门的数据差异所造成的地名检索效率低下问题,该文分析了平台中地名的表达特征,设计了面向地名信息的多级索引库组织方式,提出了地名特征词典的构建方法,设计并开发原型系统,实现了基于Lucene和地名特征词的检索框架。实验表明:多级索引通过基础索引、特征索引、分类索引三者联动的方式降低了地名检索的复杂度,具有较高的检索效率和准确度,应用于浙江省地理空间数据交换和共享平台取得了良好的效果。 相似文献
993.
针对CORS系统RTK服务盲区(RTK使用困难或无法使用)的问题,提出了在CORS系统服务盲区附近建立移动的CORS基准站。通过加密区域CORS系统的基站分布,缩短站间距,改善CORS系统网络RTK在该区域的可用性。通过设计实现的CORS移动基准站系统测试表明:在精度上,移动基准站达到与常规CORS基准站同等的效果,平面x,y≤5cm,高程H≤10cm;在可用性方面,CORS移动基准站自主供电、携带方便、组网灵活,区域网络RTK可用性明显提高。在应急测绘、救灾和临时加密CORS基准站系统等中具有借鉴和实用意义。 相似文献
994.
ArcGIS是一个建设完整GIS的软件集合,它包含了一系列部署GIS的框架:ArcGIS Desktop(专业GIS应用的完整套件)、ArcGIS Engine(定制开发GIS应用的嵌入式开发组件)、服务端GIS(ArcSDE,ArcIMS和ArcGIS Server)。ArcGIS在空间基础地理信息数据建库方面有着不可替代的作用。本文介绍ArcGIS在高速公路和国道测量中数据建库的一些应用。 相似文献
995.
肖松涛 《测绘与空间地理信息》2017,(12):161-162,166
针对城市化发展中的道路改建工程,本文以城市虚拟参考站为基础,设计了相应的测量方案。对测量成果进行分析和效益评价,得出VRS技术在大中城市的基础测绘中有较好的应用。本文涉及的道路改建工程对类似的城市测绘工作具有借鉴意义。 相似文献
996.
在坑道施工中,坑道中弯道的放线通常采用传统的偏角法,但偏角法放样的流程较烦琐,且误差累积较大,而全站仪的参考弧程序可以很好地解决上述问题。坑道施工中,采用参考线(弧)放样快速准确地进行开挖、支护及被复的定位,可以提高效率,保证工期及质量。本文以徕卡TPS800全站仪参考弧程序为例,从参考弧的定义方法、使用方法等方面,对参考弧程序进行了探讨、分析,以起到抛砖引玉的作用。 相似文献
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998.
Spatiotemporal data model for network time geographic analysis in the era of big data 总被引:1,自引:0,他引:1
Bi Yu Chen Hui Yuan Shih-Lung Shaw William H.K. Lam Xiaoling Chen 《International journal of geographical information science》2016,30(6):1041-1071
There has been a resurgence of interest in time geography studies due to emerging spatiotemporal big data in urban environments. However, the rapid increase in the volume, diversity, and intensity of spatiotemporal data poses a significant challenge with respect to the representation and computation of time geographic entities and relations in road networks. To address this challenge, a spatiotemporal data model is proposed in this article. The proposed spatiotemporal data model is based on a compressed linear reference (CLR) technique to transform network time geographic entities in three-dimensional (3D) (x, y, t) space to two-dimensional (2D) CLR space. Using the proposed spatiotemporal data model, network time geographic entities can be stored and managed in classical spatial databases. Efficient spatial operations and index structures can be directly utilized to implement spatiotemporal operations and queries for network time geographic entities in CLR space. To validate the proposed spatiotemporal data model, a prototype system is developed using existing 2D GIS techniques. A case study is performed using large-scale datasets of space-time paths and prisms. The case study indicates that the proposed spatiotemporal data model is effective and efficient for storing, managing, and querying large-scale datasets of network time geographic entities. 相似文献
999.
Since the advent of plate tectonics different global reference frames have been used to describe the motion of plates and trenches. The difference in plate motion and trench migration between different reference frames can be substantial (up to 4 cm/yr). This study presents an overview of trench migration velocities for all the mature and incipient subduction zones on Earth as calculated in eight different global reference frames. Calculations show that, irrespective of the reference frame: (1) trench retreat always dominates over trench advance, with 62–78% of the 244 trench segments retreating; (2) the mean and median trench velocity are always positive (retreating) and within the range 1.3–1.5 cm/yr and 0.9–1.3 cm/yr, respectively; (3) rapid trench retreat is only observed close to lateral slab edges (< 1500 km); and (4) trench retreat is always slow far from slab edges (> 2000 km). These calculations are predicted by geodynamic models with a varying slab width, in which plate motion, trench motion and mantle flow result from subduction of dense slabs, suggesting that trench motion is indeed primarily driven by slab buoyancy forces and that proximity to a lateral slab edge exerts a dominant control on the trench migration velocity. Despite these four general conclusions, significant differences in velocities between such reference frames remain. It is therefore important to determine which reference frame most likely describes the true absolute velocities to get an understanding of the forces driving plate tectonics and mantle convection. It is here proposed that, based on fluid dynamic considerations and predictions from geodynamic modelling, the best candidate is the one, which optimises the number of trench segments that retreat, minimizes the trench–perpendicular trench migration velocity (vT) in the centre of wide (> 4000 km) subduction zones, maximizes the number of retreating trench segments located within 2000 km of the closest lateral slab edge, minimizes the average of the absolute of the trench–perpendicular trench migration velocity (|vT|) for all subduction zones on Earth, and minimizes the global upper mantle toroidal volume flux (To) that results from trench migration and associated lateral slab migration (i.e. slab rollback or slab roll-forward). Calculations show that these conditions are best met in one particular Indo-Atlantic hotspot reference frame, where 75% of the subduction zones retreat, vT in the centre of wide subduction zones ranges between − 3.5 and 1.8 cm/yr, 83% of the trench segments located within 2000 km of the closest lateral slab edge retreat, the average of |vT| is 2.1 cm/yr, and To = 456 km3/yr (lower limit) and 539 km3/yr (upper limit). Inclusion of all the incipient subduction zones on Earth results in slightly greater fluxes of 465 km3/yr (lower limit) and 569 km3/yr (upper limit). It is also found that this reference frame is close to minimizing the total sub-lithospheric upper mantle volume flux (K) associated with motion of continental keels located below the major cratons. It is stressed, however, that K is an order of magnitude smaller than To, and thus of subordinate importance. In conclusion, the Indo-Atlantic hotspot reference frame appears preferable for calculating plate velocities and plate boundary velocities. 相似文献
1000.