A graph edit dictionary for correcting errors in roof topology graphs reconstructed from point clouds     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

In the task of 3D building model reconstruction from point clouds we face the problem of recovering a roof topology graph in the presence of noise, small roof faces and low point densities. Errors in roof topology graphs will seriously affect the final modelling results. The aim of this research is to automatically correct these errors. We define the graph correction as a graph-to-graph problem, similar to the spelling correction problem (also called the string-to-string problem). The graph correction is more complex than string correction, as the graphs are 2D while strings are only 1D. We design a strategy based on a dictionary of graph edit operations to automatically identify and correct the errors in the input graph. For each type of error the graph edit dictionary stores a representative erroneous subgraph as well as the corrected version. As an erroneous roof topology graph may contain several errors, a heuristic search is applied to find the optimum sequence of graph edits to correct the errors one by one. The graph edit dictionary can be expanded to include entries needed to cope with errors that were previously not encountered. Experiments show that the dictionary with only fifteen entries already properly corrects one quarter of erroneous graphs in about 4500 buildings, and even half of the erroneous graphs in one test area, achieving as high as a 95% acceptance rate of the reconstructed models.  相似文献   

Direct georeferencing of oblique and vertical imagery in different coordinate systems     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

Reconstruction of 3D models through integrating vertical and oblique imagery has been studied extensively. For a 3D reconstruction, object point cloud coordinates could be calculated using direct georeferencing (DG) obtained from the direct orientation data of a GPS/INS system. This paper implemented DG approaches for vertical and oblique imagery in the earth centered earth fixed frame (e-frame), local tangent frame (l-frame), and map projection frame (p-frame), respectively. In the p-frame, the earth curvature correction formulas were derived through naturalizing oblique imagery to vertical imagery to achieve a high positioning precision. Five basic stereo-pair models for vertical and oblique imagery were simulated to verify the positioning accuracy of different frames. Simulation experiments showed that DG in the e-frame and l-frame of these five scenarios were rigorous, and no systematic errors were imported by the DG model as these frames are Cartesian. DG in the p-frame has obvious systematic errors which are aroused by the earth curvature and projection deformation unconformity in the vertical and horizontal directions. These errors, however, can be compensated effectively through correcting image coordinates of the oblique imagery by extending the standard image coordinate correction approach and the exterior orientation (EO) height term. After the correction, the absolute positioning error is lower than 1/20 GSD for simulation test-1. In the p-frame, the process is straightforward, and it is convenient for producing maps. For high accuracy DG, though, it is recommended to adopt e-frame or l-frame options.  相似文献   

Recovery of elevation from estimated gradient fields constrained by digital elevation maps of lower lateral resolution     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

Depth measurement techniques like stereo analysis and laser range scanning often yield a lateral resolution below image resolution. In contrast, shading-based methods estimate the elevation model at image resolution. We present a computationally efficient approach to recover a surface of high vertical and high lateral resolution from a noisy gradient field and independently measured elevation data of lower lateral resolution, relying on a minimization of the mean squared difference between the low-pass component of the surface obtained based on shading information and that of the independently measured elevation data. The presented method is compared to a reference approach that minimizes a weighted sum comprised of the mean squared difference between the low-pass components of the estimated gradient field and the optimized model, respectively. The presented algorithm is applied using lunar orbital image data and stereo elevation data and is evaluated regarding orbital laser altimeter measurements of high vertical accuracy.  相似文献   

基于神经网络的全球三维温盐场重构技术研究     

聂旺琛  王喜冬  陈志强  何子康  范开桂 《热带海洋学报》2022,41(2):1-15

文章利用果蝇优化广义回归神经网络算法FOAGRNN (fruit fly optimization algorithm, FOA; generalized regression neural network, GRNN)对SODA (simple ocean data assimilation)再分析数据进行训练, 构建海表温度、盐度、海面高度与次表层温盐场之间的投影关系模型, 并在全球范围使用SODA和卫星遥感数据评估了模型的应用性能。首先, 利用独立的2016年SODA海表数据作为模型输入进行理想重构试验, 结果显示全球重构温、盐平均均方根误差(MRMSE)分别为0.36℃和0.08‰, 与世界海洋图集WOA13资料相比减小约50%和60%。然后, 利用卫星观测的海表信息作为模型输入进行实际应用试验, 并与Argo观测剖面进行比较评估。试验结果表明, 重构模型能有效表征海水温、盐特征, 其中重构温、盐MRMSE分别为0.79℃和0.16‰, 相比WOA气候态减小27%和11%。误差的垂向分布显示, 重构温度RMSE从海表向下迅速增大, 至100m达到峰值1.35℃, 而后又迅速回落,至250m处为0.81℃, 跃层往下不断减小; 重构盐度RMSE基本随深度增大而减小, 误差峰值位于25m附近, 约为0.25‰。此外, Argo浮标跟踪分析和区域水团统计结果也表明模型能够较好地刻画海洋三维温盐场的内部结构特征。  相似文献   

A visible band index for remote sensing leaf chlorophyll content at the canopy scale     

《International Journal of Applied Earth Observation and Geoinformation》2013

Leaf chlorophyll content is an important variable for agricultural remote sensing because of its close relationship to leaf nitrogen content. The triangular greenness index (TGI) was developed based on the area of a triangle surrounding the spectral features of chlorophyll with points at (670 nm, R₆₇₀), (550 nm, R₅₅₀), and (480 nm, R₄₈₀), where R_λ is the spectral reflectance at wavelengths of 670, 550 and 480, respectively. The equation is TGI = −0.5[(670 − 480)(R₆₇₀ − R₅₅₀) − (670 − 550)(R₆₇₀ − R₄₈₀)]. In 1999, investigators funded by NASA's Earth Observations Commercialization and Applications Program collaborated on a nitrogen fertilization experiment with irrigated maize in Nebraska. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data and Landsat 5 Thematic Mapper (TM) data were acquired along with leaf chlorophyll meter and other data on three dates in July during late vegetative growth and early reproductive growth. TGI was consistently correlated with plot-averaged chlorophyll-meter values at the spectral resolutions of AVIRIS, Landsat TM, and digital cameras. Simulations using the Scattering by Arbitrarily Inclined Leaves (SAIL) canopy model indicate an interaction among TGI, leaf area index (LAI) and soil type at low crop LAI, whereas at high LAI and canopy closure, TGI was only affected by leaf chlorophyll content. Therefore, TGI may be the best spectral index to detect crop nitrogen requirements with low-cost digital cameras mounted on low-altitude airborne platforms.  相似文献   

Forman相位校正算法的改进与实现     

马利春  杨仁忠  石璐 《国土资源遥感》2013,25(3)

针对直接采用Forman相位校正算法实现HJ-1A高光谱数据实时光谱复原处理系统过程中遇到的算法复杂、运算量大以及运算效率低的问题,提出了改进的Forman算法.该算法简化了相位数据的计算,并利用复数序列傅里叶变换的性质和实序列傅里叶变换的共轭对称性优化了计算过程.在分析改进前后算法关键步骤的浮点数运算量的基础上,以HJ-1A高光谱数据为实验对象,基于图形处理器(graphic processing unit,GPU)实现了改进的Forman算法.结果表明:在相同计算精度的情况下,改进的Forman算法运算速度提高了11.86％,为HJ-1A高光谱数据实时光谱复原处理系统的实现提供了行之有效的方法.  相似文献   

利用梯度重建的稳健多频InSAR相位解缠方法   总被引：1，自引：0，他引：1  

葛仕奇  陈亮  丁泽刚  龙腾 《测绘学报》2013,42(3):367-373,396

为解决常规InSAR系统因干涉相位欠采样所导致的陡峭地区高程提取困难问题,提出一种利用多频干涉量进行相位梯度重建并实现相位解缠的处理方法。基于干涉相位的统计分布特性,研究了多频InSAR相位梯度的最大似然估计原理,针对有限观测频点情况下梯度解模糊性能对相位噪声敏感的问题,提出通过基于邻点集的局部曲面建模进行相位梯度重建的稳健算法,并从频点选择、估计区间限定等方面进一步研究了提高算法稳健性的途径。最后通过对仿真和实际DEM数据的试验,验证该方法的有效性。  相似文献   

基于CORS数据反演江苏上空电离层电子密度     

刘三枝  王解先  李浩军 《测绘科学》2013,38(2)

本文利用IRI2007模型和江苏CORS网数据,结合附加约束的同时迭代重构算法,反演了地磁平静日江苏上空电子密度的结构分布。结果表明,整个研究区域电子密度在不同纬度和不同高度上存在明显的日变特征,电子密度最大值出现在北京时13～15时,随着时间推移,峰值幅度衰减;白天出现明显的E层,夜晚消失;反演结果说明了电离层三维层析技术为监测电离层时空结构提供了一种强有力的实验支持。  相似文献   

1∶500地形图建库的技术与方法     

朱旗  左志进 《地理空间信息》2013,11(1):119-121,15

通过对地形图数据进行分析,设计数据建库方案,利用FME、AutoCAD编制相关数据入库程序和质量检查软件,构建了从CAD的dwg数据到GIS的数据库数据的无损转换模型。实际生产表明,该方法实现了从CAD的dwg数据到GIS的数据库数据的空间和属性信息的快速、无损转换,是一种可行的地形图数据建库方案。  相似文献   

基于Skyline三维模型重建的关键方法及其应用     

胡荣  张旻 《地理空间信息》2013,(3):90-92

对Skyline三维模型重建过程中的数据预处理及建模关键技术进行了研究;并基于该平台,充分利用已有的传统的地理空间数据,将其应用到武汉大学信息学部局部校区的三维模型重建中,取得了较好的效果。  相似文献