QZSS L6E增强服务改正数支持的PPP性能评估     

朱轶群  吴继忠 《测绘科学》2021,46(2):34-41

准天顶卫星系统目前利用QZS-2~QZS-43颗卫星播发L6E信号,为东亚和大洋洲地区用户提供实时的增强服务。该文分析了L6E信号结构及轨道和钟差的计算模型,研究了目前L6E信号的覆盖范围和可用性,评估了L6E改正数恢复的卫星轨道和钟差及其用于动态PPP的精度水平。结果表明:我国用户在使用15°截止高度角时L6E信号仍有100%的可用性;L6E改正数恢复的GPS和GLONASS卫星轨道的3D RMS平均值分别为5.3和13.9 cm,卫星钟差的STD平均值分别为0.14和0.22 ns,利用GPS卫星的轨道和钟差进行的动态PPP可以获得水平优于10 cm、高程优于15 cm的精度,在加入GLONASS卫星后,东方向和高程方向定位误差和收敛时间均有明显改善。  相似文献   

面向室内地图多尺度表达的POI符号设计与实现     

谭金蓉  黄丽娜  肖屹  武光莹 《测绘地理信息》2021,46(1):83-87

为了满足人们获取室内空间信息时多层次的认知需求,从室内空间的特点出发,以商城为例,对室内要素的分类分级体系进行梳理,在此基础上探讨兴趣点(point of inte-rest,POI)多尺度表达的符号模型;结合地图比例尺和用户需求设计了一套易于理解又能多层次表征要素信息的室内地图POI符号系统,并通过典型案例对其可行性进行制图实践检验。实践结果表明,所提出的多尺度POI符号化方案具有可行性,设计的符号集可以广泛运用到其他商城中,该思想可以运用于其他类型的室内地图。  相似文献   

Regional representation of glaciers in Chandra Basin region,western Himalaya,India     

Pratima Pandey  S. Nawaz Ali  AL. Ramanathan  P.K. Champati ray  G. Venkataraman 《地学前缘(英文版)》2017,8(4):841-850

Hamtah and Chhota Shigri are two nearby, well monitored glaciers of western Himalaya, lying in the same climatic zone and driven by the same climatic conditions. In this study, topographical characteristics of both the glacier have been explored to understand the role of topography in controlling the glacier response. Further, their topographical characteristics and possible response towards climatic variations have been compared with each other and also with that of the other glaciers in the basin to find out the suitability of these two glaciers to be considered as representative of the region. Multi sensor and multi temporal remote sensing data have been used to carry out to fulfill the objectives. It is found that being in the same climatic zone, the mean accumulation area ratio of Chhota Shigri is 54% and Hamtah is 11% between 1980 and 2014. In comparison to Hamtah, Chhota Shigri glacier has a small upslope area, low compactness ratio indicating the ability of the glacier to receive direct precipitation and solar radiation. The analysis revealed that the Chhota Shigri glacier has a closer resemblance with the other glaciers in the region than Hamtah glacier. Also, the topographical settings of Chhota Shigri glacier are suitable for recording and reflecting year-to-year climatic variations.  相似文献   

顾及形变控制的小屏幕变比例尺交通路线图生成方法     

王俪颖  遆鹏  喻崇湖  赵东旭  侯晓彤 《地球信息科学学报》2017,19(9):1245-1252

用户在旅游或者室外运动中经常将路线图显示于移动设备上以方便规划路线。然而移动设备显示屏幕通常较小,若较大范围的地图通过等比例尺缩小在小屏幕显示,可能会导致清晰度和辨识度的降低,尤其对于地图中地物较为密集的区域。本文提出一种自动化生成变比例尺地图的方法,通过更加均匀化地图显示内容密度分布以改善地图概览清晰度。在该方法中,首先对密度分布进行估计,密度估计主要考虑地图上路线空间分布以及地标与注记显示空间,然后根据所得到的密度分布进行变比例尺转换,最终生成的变比例尺结果图,其大小取决于给定显示尺寸。相较于现有变比例尺转换方法,本文提出的方法可以考虑了地标与注记显示空间,同时又能有效控制地图变形以提高地图识别。实验结果表明,通过本方法生成变比例尺结果图对地图概览的清晰度有着显著提高,并且能够保持良好的地图识别度。  相似文献   

基于XML Web服务的地图增量更新模型研究     

陈胜林  方鹏  高玉荣 《测绘工程》2010,19(6):53-56

从地图表达数据可持续利用的角度,提出基于XML Web服务的地图增量更新模型。分析基于Web服务的地图增量更新的原理、关键技术以及实现过程,并结合GML、XSLT表达规则、SVG地图符号及JavaScript设计,实现基于XML的地图表达数据增量更新的原型系统。  相似文献   

虚拟地理环境认知与表达研究初步   总被引：4，自引：0，他引：4  

林珲  黄凤茹  鲁学军  胡明远  徐丙立  武磊 《遥感学报》2010,14(4):831-838

分析了地理学的地理环境与当前地理信息技术中的地理空间两者概念之间的差异,探讨了地图与地理信息系统空间认知的发展及特点,初步研究了虚拟地理环境认知与表达的对象、特征与主要内容。从基于虚拟地理环境的地理认知和基于地理认知的虚拟地理环境表达两个层面分析了虚拟地理环境的认知与表达;指出虚拟地理环境的认知与表达研究不仅需要进一步发展地理空间认知理论和方法,还需要拓展对地理过程及人类行为的认知与表达理论和方法研究;并着重探讨了地理过程的表达和人类行为的模拟,指出当前虚拟地理环境认知与表达研究的关键内容。  相似文献   

Spatial rules that generate urban patterns: Emergence of the power law in the distribution of axial line length     

Hani Rezayan  Mahmoud Reza Delavar  Andrew Ulrich Frank  A. Mansouri 《International Journal of Applied Earth Observation and Geoinformation》2010

This paper studies emergence/generation of power law in rank-order distribution of axial line length, which is a global pattern observed in real cities, due to interaction of a set of seven simple spatial rules at a local scale. These rules and their interactions form a model expected to simulate the morphological structure of free spaces in unplanned organic pedestrian small cities. Effects of each of the seven rules are discussed through repeated simulations of eight possible combinations of the rules, using a bottom-up process. The results show that the rules generate environments with statistically stable rank-order distribution of axial line length that follows the power law. It means that the axial maps of the simulated environments have a scale-free hierarchical structure such that their distributions lean toward short axial lines. It also represents dominance of local spatial structure, as the model renders a faster rate of growth at a local scale while allowing a steady growth at a global scale.  相似文献   

3D Seismic survey design using mixed-radix based algorithm inversion     

Atahebson B. Santos  Milton J. Porsani  Manuelle S. Góis 《Geophysical Prospecting》2019,67(7):1720-1731

The determination of three-dimensional geometry and acquisition parameters, the seismic acquisition survey design, is constantly subject of studies in obtaining data with the highest seismic quality, operational efficiency and cost minimization. In this paper, we propose a methodology for inverting geometry parameters of three-dimensional orthogonal land seismic surveys based on a direct search method using a mixed-radix based algorithm. In this algorithm, the search space is discretized on a mixed-radix base, which depends on the extreme values and the search resolution of each parameter. We will show how to reparametrize the orthogonal acquisition geometry elements in order to obtain the independents and integers parameters that are necessary to construct the mixed-radix base. For the optimization purpose, we define an objective function to contemplate target parameters associated with the elements of the acquisition geometry directly related to the geophysical and operational constraints. Taking in account that the mathematical functions and the objective function we define for the problem have no significant computational cost, all model space parameters are fast and efficiently tested. We applied the algorithm, using as input data, provided by a one-line roll orthogonal reference geometry, assuming a pair of geological objectives as shallow and deep targets. All selected models that meet both the proposed objectives and the constraints are organized by decreasing order of fitness so that with the mixed-radix inversion algorithm we found not only the best model, but also a set of suitable models. Likewise, with the best set of geometries, it is possible to establish a direct comparison between them, analysing their adherence to the technical and operational requirements according to the availability and degree of detail of each one. We show the top 10 best results as a table, allowing a direct comparison between all aspects of these geometries, and we summarize the results showing graphically the fitness of all selected geometries and the inverted geometry elements for the 1000 best geometries. These graphical displays provide a direct way to understand how each model behaves as the fitness decreases. The algorithm is very flexible and its application can be extended to any environment and type of acquisition geometry, and in any phase study of an area be it regional, exploratory or development.  相似文献   

Schwinger Bose实现下自旋相干态Wigner函数的特性分析          下载免费PDF全文

宋军  范洪义 《海洋学报》2010,32(10):6806-6813

在Schwinger Bose实现下,引入纠缠态表象及Wigner算符在该表象下的表示,得到自旋相干态的Wigner函数,数值计算画出相空间中Wigner函数的分布图,并加以分析,发现在Schwinger Bose实现下自旋相干态确实体现出纠缠特性.  相似文献