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341.
本文论述了目标图像的形态分解、形态分布函数和形态谱函数的基本概念和具体算法,它们是研究数字地图图像的形态分解与表示的主要内容。 相似文献
342.
本文主要就分级布设的变形监测网的灵敏度问题进行讨论,并就在实际工作中如何直接、有效地改善监测网的灵敏度提出了有益的建议. 相似文献
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345.
利用GEOSAT/ERM卫星测高数据计算中国近海海平面 总被引:5,自引:1,他引:5
本文利用一年(1986年11月8日~1987年11月17日)22个ERM周期的GEOSAT卫星测高数据计算出中国近海海域(105°~135°E,0°~40°N)相对于GRS80参考椭球面的1°×1°年平均海平面。该海平面我们称之为IGGMSS95平均海平面。在数据处理过程中,由于采用了混合轨道误差模型及交叠平差技术,极大地消除了在误差中占主要成分的径向轨道误差影响,使得IGGMSS95平均海平面的总体精度达到±20~30cm(RMS)水平。与OSU91A重力大地水准面模型相比较可以发现两者具有惊人的一致性。 相似文献
346.
The demand for analysis of large‐scale data has increased with increased access to spatial vector data. Polygon overlay of vector data in a virtual globe requires proprietary data structures and proprietary analysis algorithms. A vector data structure is designed for rapid polygon overlay in a virtual globe by recording the metadata of the triangles (TriMeta) that constitute polygons. A polygon overlay algorithm is proposed based on this data structure. The overlay of two complex GIS polygons is transformed into the intersection computation of their 3D triangular presentations. The intersection computation of two sets of triangles is reduced considerably by utilizing TriMeta to filter out the disjoint triangle pairs and rapidly identify the contained triangle. The new method improves the overlay efficiency in a virtual globe because the amount of computation required to calculate the intersections of two large polygons and drape the intersections onto a terrain surface is reduced. 相似文献
347.
ABSTRACTThis paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions. Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing, and to produce centimeter-resolution topographic products in near real-time after landing. Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing. During surface operations, visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images. The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning, science target selection and scientific investigations. A GIS-based digital cartography system was also developed to support rover teleoperation. 相似文献
348.
ABSTRACT Spatial heterogeneity represents a general characteristic of the inequitable distributions of spatial issues. The spatial stratified heterogeneity analysis investigates the heterogeneity among various strata of explanatory variables by comparing the spatial variance within strata and that between strata. The geographical detector model is a widely used technique for spatial stratified heterogeneity analysis. In the model, the spatial data discretization and spatial scale effects are fundamental issues, but they are generally determined by experience and lack accurate quantitative assessment in previous studies. To address this issue, an optimal parameters-based geographical detector (OPGD) model is developed for more accurate spatial analysis. The optimal parameters are explored as the best combination of spatial data discretization method, break number of spatial strata, and spatial scale parameter. In the study, the OPGD model is applied in three example cases with different types of spatial data, including spatial raster data, spatial point or areal statistical data, and spatial line segment data, and an R “GD” package is developed for computation. Results show that the parameter optimization process can further extract geographical characteristics and information contained in spatial explanatory variables in the geographical detector model. The improved model can be flexibly applied in both global and regional spatial analysis for various types of spatial data. Thus, the OPGD model can improve the overall capacity of spatial stratified heterogeneity analysis. The OPGD model and its diverse solutions can contribute to more accurate, flexible, and efficient spatial heterogeneity analysis, such as spatial patterns investigation and spatial factor explorations. 相似文献
349.
传统的RTK(实时动态定位)终端检测采用静态基线数据解算的方法,该检测方法与RTK终端实际动态应用场景不符,无法满足动态检测需要。通过研制高精度的车载导航基准设备和开发车载动态检测软件,同时解决车载设备数据的同步问题,提出基于车载移动平台的实时动态RTK终端检测技术。车载基准设备和待检测设备可以动态解算同源数据并实时上发结果,软件处理中心通过比对处理解算结果,对待检测设备进行检测评价。实验结果表明,设计所得的车载系统可稳定运行,并实现动态检测过程。同时,在良好的观测条件下,检测精度平面方向达到1cm,高程方向达到2cm,实现高精度实时动态检测的目的。 相似文献
350.
Jiangfeng She Xiaoyan Gu Junzhong Tan Ming Tong Chaofan Wang 《Transactions in GIS》2019,23(2):275-293
The simplification of 3D building models to effectively reduce model complexity and improve rendering efficiency is an important component of 3D GIS. To reduce the data volume while preserving the model appearance, this article proposes a novel simplification method for complex 3D building models. Texture discontinuities are addressed by developing a new data model that records the mapping relation between the texture coordinates of each vertex and its neighboring triangles. The surface mesh of the building model is then segmented into regions, guided by topology and appearance. Finally, the mesh segmentation information is used to derive an improved error metric that considers both geometric and texture errors, and the texture coordinates are adjusted after each simplification operation. A series of comparative experiments alongside traditional methods demonstrates that our approach achieves a good balance between geometric fidelity and texture preservation, and produces simplified 3D building models with better visual quality. 相似文献