共查询到20条相似文献，搜索用时 31 毫秒
1.
Geostatistical characterization of local DEM error is usually based on the assumption of a stationary variogram model which requires the mean and variance to be finite and constant in the area under investigation. However, in practice this assumption is appropriate only in a restricted spatial location, where the local experimental variograms vary slowly. Therefore, an adaptive method is developed in this article to model non‐stationary variograms, for which the estimator and the indicator for characterization of spatial variation are a Voronoi map and the standard deviation of mean values displayed in the Voronoi map, respectively. For the adaptive method, the global domain is divided into different meshes with various sizes according to the variability of local variograms. The adaptive method of non‐stationary variogram modeling is applied to simulating error surfaces of a LiDAR derived DEM located in Sichuan province, China. Results indicate that the locally adaptive variogram model is more accurate than the global one for capturing the characterization of spatial variation in DEM errors. The adaptive model can be considered as an alternative approach to modeling non‐stationary variograms for DEM error surface simulation. 相似文献
2.
Changqing Yan Jimin Liu Gang Zhao Chuanfa Chen Tianxiang Yue 《Transactions in GIS》2016,20(6):991-1003
A high accuracy surface modeling method (HASM) has been developed to provide a solution to many surface modeling problems such as DEM construction, surface estimation and spatial prediction. Although HASM is able to model surfaces with a higher accuracy, its low computing speed limits its popularity in constructing large scale surfaces. Hence, the research described in this article aims to improve the computing efficiency of HASM with a graphic processor unit (GPU) accelerated multi‐grid method (HASM‐GMG). HASM‐GMG was tested with two types of surfaces: a Gauss synthetic surface and a real‐world example. Results indicate that HASM‐GMG can gain significant speedups compared with CPU‐based HASM without acceleration on GPU. Moreover, both the accuracy and speed of HASM‐GMG are superior to the classical interpolation methods including Kriging, Spline and IDW. 相似文献
3.
Tian‐Xiang Yue Na Zhao Hai Yang Yin‐Jun Song Zheng‐Ping Du Ze‐Meng Fan Dun‐Jiang Song 《Transactions in GIS》2013,17(6):943-952
A method of high accuracy surface modeling (HASM) has been constructed to find a solution for error problems that had long troubled surface modeling in geographical information systems (GIS). It is found that when a preconditioned conjugate gradient (PCG) algorithm is used to solve the large sparse linear system, which HASM can be transferred into, HASM performs best in terms of simulation compared with all other algorithms. But its computing speed is not fast enough for all applications. A multi‐grid method is introduced into HASM to try to shorten its computing time. Both numerical and real‐world tests demonstrate that there is a range of stop error (SE). The multi‐grid method of HASM (HASM‐MG) greatly increases computing speed when SEs are within this range, compared with the PCG algorithm of HASM (HASM‐PCG). HASM‐MG is suitable for applications with a need for less accuracy and a shorter computing time. HASM‐PCG is appropriate for issues needing higher accuracy. HASM‐MG performs better than HASM‐PCG in flat areas, while HASM‐PCG does better in complex terrainm in terms of accuracy and computing time. 相似文献
4.
High accuracy surface modeling (HASM) constructed based on the fundamental theorem of surface is more accurate than the classical methods. However, because of boundary error, location error, etc, HASM has a big accuracy loss in real-world examples. In former researches we solved the location error with Taylor expansion. In order to reduce the HASM boundary error and improve its accuracy further, this paper presents a new method of Laplace interpolation to compute the region boundary value. Gaussian synthetic surface and the real world test region are employed to validate the efficiency of this method. Results show that the boundary value computed with Laplace interpolation is more accurate than the classical methods, which can be regarded as an alternative for boundary value computation. 相似文献
5.
本文在讨论地球表层概念和地球表层建模定义的基础上,总结分析了地球表面形态表达、地球气候系统模拟、生态系统空间模拟分析和地球表层模拟系统等主要研究进展。分析结果表明,误差问题、多尺度问题、地球表层模拟速度问题和三维实时可视化问题是地球表层建模面临的主要挑战。为了解决这些问题,必须发展和采用诸如以遥感数据为初始场、以地面实测数据为优化控制条件的高精度高速度曲面建模新方法和新思路。 相似文献
6.
The HASM(high accuracy surface modeling) technique is based on the fundamental theory of surfaces,which has been proved to improve the interpolation accuracy in surface fitting.However,the integral iterative solution in previous studies resulted in high temporal complexity in computation and huge memory usage so that it became difficult to put the technique into application,especially for large-scale datasets.In the study,an innovative model(HASM-AD) is developed according to the sequential least squares on... 相似文献
7.
从高精度曲面建模方法（HASM）曲面方程出发,结合数据平差理论,建立了基于独立单元的计算模型,并且采用逐次最小二乘法对计算方程进行分组求解。对HASM-AD和几种经典方法的精度进行了交叉验证,结果表明,该算法模拟误差的均方根差远小于其他空间插值方法。 相似文献
8.
为了提高Gass-Seidel(GS)算法的收敛速度,提出了改进的GS算法(MGS),用于解算高精度曲面模型(HASM)(HASM-MGS)。以高斯合成曲面为研究对象,将HASM-MGS与HASM-GS和Matlab提供的函数进行对比,结果表明,达到相同的模拟中误差,HASM-MGS计算时间远小于HASM-GS和Matlab提供的函数;HASM-MGS计算时间与模拟区域的网格数呈非常好的线性关系,时间复杂度比传统的方法降低两个数量级。 相似文献
9.
基于曲面论原理的高精度曲面建模方法（HASM）解决了长期困扰地理信息系统界的误差问题,但使用该方法需要求解大规模线性方程系统导致其计算效率较低并限制了其广泛应用。为提高HASM线性系统的解算速度和精度,本文基于二维双连续投影提出了一种解算HASM的新方法（HASM-DSPM）。为了提高收敛速度和解算精度,该方法采用选取优化的投影空间和两次校正策略。理论分析表明,使用该方法比使用高斯赛尔方法（Gauss-Seidel, GS）和改进的高斯赛德尔方法(Modified Gauss-Seidel, MGS)效率明显提高。分别用本文引入的方法、高斯赛德尔方法和效率较高的MGS方法分别进行了HASM方程组的解算,并对高斯合成曲面和实际项目区模拟进行了模拟试验。结果表明,和GS、MGS方法相比,本文提出的HASM-DSPM解算方法无论收敛速度和计算时间都有明显改善。 相似文献
10.
基于条件模拟的DEM误差曲面实现研究 总被引：2，自引：1，他引：1
为了克服DEM全局误差指标描述DEM精度的缺陷,基于条件模拟(CS)实现了DEM误差曲面的构建。构建了甘肃省董志塬某测区DEM误差曲面,并与普通Kriging(OK)插值结果进行了比较。结果表明,OK具有明显的平滑效应,而CS能准确反映DEM误差的空间波动性。DEM误差对坡度精度的影响分析表明,相比地形复杂的区域,DEM误差严重影响平坦区域的坡度精度;对测区水土流失等级划分结果的分析表明,约有70.2%的网格点的等级划分受DEM误差的影响。 相似文献
11.
基于高精度曲面模型的DEM构建与误差分析 总被引：1，自引：1，他引：0
引入地形表达误差(terrain representation error,Etr),选择标准曲面和甘肃省董志塬地区作为研究对象,利用窗口分析法实现Etr的提取;用统计分析法得出Etr随网格分辨率变化的回归方程;根据误差传播定律计算DEM中误差。数值结果表明,该方法能更准确的计算HASM生成的DEM精度;相同的采样数下,HASM较传统方法(IDW,Spline和Kriging)能生成更高精度和分辨率的DEM。在难以获取已知数据的地区,HASM提供了生成相对准确DEM的高效工具。 相似文献
12.
Classification and regression tree (CART) has been widely implemented to estimate impervious surface, an important indicator of urbanization and environmental quality. Although the CART algorithm gains higher overall accuracy than linear regression models, only very few studies have noticed that reliability of CART is affected by systematic errors. Especially, CART typically overestimates impervious surfaces in low-density urban areas and underestimates them in high-density urban areas. The primary objective of this study is to develop an improved integrated method to estimate impervious surface with higher accuracy by reducing the systematic errors of CART. This improved method was applied to three urban areas, Chicago (United States), Venice (Italy), and Guangzhou (China) to examine its effectiveness. When compared with the conventional CART, overall mean average error (MAE) and root mean square error (RMSE) of improved method are decreased by 22.64% and 20.93%, respectively, and R2 rises from 0.9 to 0.96. In high-density impervious surfaces, where intensely developed urban area is located, the MAE and RMSE for the improved method are 0.066 and 0.088, respectively, largely improved from 0.100 to 0.130. Since accurate estimation of high-density impervious surfaces is the fundamental issue for monitoring and understanding the urban environment, the improved method demonstrated in this study is significant. 相似文献
13.
We describe a demodulation scheme for the navigation message of GPS receivers on spin-stabilized rockets. Doppler frequencies due to fast and complex dynamics, in particular high-rate spin, cause errors in carrier frequency tracking. The effects of such errors on navigation message demodulation are described through theoretical analysis and numerical simulation. A demodulation scheme that includes a frequency estimator is proposed to account for frequency tracking errors. It is demonstrated that demodulation performance is degraded 5 dB due to frequency uncertainty. Simulation results showed that a demodulator which includes maximum likelihood (ML) frequency estimator achieves near-optimal symbol error rate under these conditions. Demodulation with ML estimator achieves a bit error rate below 10?5 for a C/N 0?=?35 dB–Hz, for spin rates below 2.7?Hz, and a rocket radius smaller than 1 m. For the cases in which computational capabilities of the on-board GPS receiver is insufficient to implement the demodulator with ML estimator, frequency estimation methods with low complexity were also tested through numerical simulation. The proposed Kay and Quinn-Fernandes combination achieves a bit error rate below 10?5 for a C/N 0?=?37 dB–Hz while requiring 1/10 of processing time. 相似文献
14.
利用雷达干涉数据进行城市不透水层百分比估算 总被引：2，自引：0，他引：2
人工不透水层是城市地区的重要特征.作为城市生态环境的关键指数,不透水层百分比(Impervious Surfaces Percentage, ISP)常用于城市水文过程模拟、水质面源污染及城市专题制图等研究中.本文利用ERS-1/2 重复轨道雷达干涉数据,采用分类与回归树(CART)算法探究了雷达遥感在城市ISP估算中的可行性和潜力,并与SPOT5 HRG光学遥感图像的估算结果进行了分析比较.香港九龙港岛实验区的初步研究结果表明,雷达干涉数据在城市不透水层研究中具有一定的应用潜力,特别是裸土和稀疏植被的ISP估算结果要好于光学遥感,这主要得益于雷达干涉数据(特别是长时间相干图像)在人工建筑物和裸土或稀疏植被之间具有很强的区分能力,另外,雷达干涉数据和光学遥感数据间的融合能够提高ISP估算精度. 相似文献
15.
Positional Accuracy of Spatial Data: Non-Normal Distributions and a Critique of the National Standard for Spatial Data Accuracy 总被引：5，自引：0，他引：5
Paul A Zandbergen 《Transactions in GIS》2008,12(1):103-130
Spatial data quality is a paramount concern in all GIS applications. Existing spatial data accuracy standards, including the National Standard for Spatial Data Accuracy (NSSDA) used in the United States, commonly assume the positional error of spatial data is normally distributed. This research has characterized the distribution of the positional error in four types of spatial data: GPS locations, street geocoding, TIGER roads, and LIDAR elevation data. The positional error in GPS locations can be approximated with a Rayleigh distribution, the positional error in street geocoding and TIGER roads can be approximated with a log‐normal distribution, and the positional error in LIDAR elevation data can be approximated with a normal distribution of the original vertical error values after removal of a small number of outliers. For all four data types considered, however, these solutions are only approximations, and some evidence of non‐stationary behavior resulting in lack of normality was observed in all four datasets. Monte‐Carlo simulation of the robustness of accuracy statistics revealed that the conventional 100% Root Mean Square Error (RMSE) statistic is not reliable for non‐normal distributions. Some degree of data trimming is recommended through the use of 90% and 95% RMSE statistics. Percentiles, however, are not very robust as single positional accuracy statistics. The non‐normal distribution of positional errors in spatial data has implications for spatial data accuracy standards and error propagation modeling. Specific recommendations are formulated for revisions of the NSSDA. 相似文献
16.
应用求解沿轨迹重力异常的垂线偏差法以及求解空间分辨率的交叉谱分析法,建立了高度计测距精度与沿轨迹重力异常反演精度以及空间分辨率的关联性模型。首先依据卫星测高原理,给出了沿轨迹重力异常的误差传播公式,然后以此为基础通过推导交叉谱分析中一致性系数与信噪比的数学表达式,建立了高度计测距精度与空间分辨率的解析关系。数值仿真结果表明:雷达高度计测距精度与沿轨迹重力异常反演精度成正比关系,与空间分辨率成幂函数关系,即高度计测距精度提高m倍,沿轨迹重力异常反演精度提高m倍,全球海域平均空间分辨率提高m0.464 4倍。将数值仿真结果与相关文献中对实际测高数据的处理结果进行比较,验证了理论分析及模型的正确性。 相似文献
17.
可靠性作为分析结果评价的质量指标,同时也是分析模型构建的优化准则。在传统测绘领域,李德仁于20世纪80年代中期提出了两个多维备选假设的模型误差可区分理论和验后方差选权迭代的粗差剔除方法,发展了测量平差可靠性理论及摄影测量应用。在电磁物理和普适计算支持下,传统测绘技术已经进化为现代地球空间信息科技。随之,可靠性理论内容从测量平差的粗差处理、空间数据分析的异常处理延伸到空间信息服务的可信计算,可靠性分析方法也从统计推断、优化计算延伸到逻辑推理。类比语言学,测量平差的粗差处理为语法分析,空间分析的异常处理为语义分析,空间信息服务的可信计算则为语用分析。简要地给出了空间数据分析的可靠性指标计算方法,分析了优化目标（成本或代价）函数构造的一般准则（物理系统的能量最小化、数据系统的信息量最大化和用户系统的决策风险最小化）,指出可靠性理论方法呈现整体模拟趋势（正常和异常的相对整体性,外在数据和内在状态的相对整体性,静态结构和动态行为的相对整体性,人机地系统的相对整体性）。 相似文献
18.
Least-squares collocation with covariance-matching constraints 总被引：1，自引：0，他引：1
Christopher Kotsakis 《Journal of Geodesy》2007,81(10):661-677
Most geostatistical methods for spatial random field (SRF) prediction using discrete data, including least-squares collocation
(LSC) and the various forms of kriging, rely on the use of prior models describing the spatial correlation of the unknown
field at hand over its domain. Based upon an optimal criterion of maximum local accuracy, LSC provides an unbiased field estimate
that has the smallest mean squared prediction error, at every computation point, among any other linear prediction method
that uses the same data. However, LSC field estimates do not reproduce the spatial variability which is implied by the adopted
covariance (CV) functions of the corresponding unknown signals. This smoothing effect can be considered as a critical drawback
in the sense that the spatio-statistical structure of the unknown SRF (e.g., the disturbing potential in the case of gravity
field modeling) is not preserved during its optimal estimation process. If the objective for estimating a SRF from its observed
functionals requires spatial variability to be represented in a pragmatic way then the results obtained through LSC may pose
limitations for further inference and modeling in Earth-related physical processes, despite their local optimality in terms
of minimum mean squared prediction error. The aim of this paper is to present an approach that enhances LSC-based field estimates
by eliminating their inherent smoothing effect, while preserving most of their local prediction accuracy. Our methodology
consists of correcting a posteriori the optimal result obtained from LSC in such a way that the new field estimate matches
the spatial correlation structure implied by the signal CV function. Furthermore, an optimal criterion is imposed on the CV-matching
field estimator that minimizes the loss in local prediction accuracy (in the mean squared sense) which occurs when we transform
the LSC solution to fit the spatial correlation of the underlying SRF. 相似文献
19.
In mountainous regions, solar radiation exhibits a strong spatial heterogeneity due to terrain shading effects. Terrain shading algorithms based on digital elevation models can be categorized into two types: area‐based and point‐specific. In this article, we evaluated two shading algorithms using designed mathematic surfaces. Theoretical shading effects over four Gauss synthetic surfaces were calculated and used to evaluate the terrain shading algorithms. We evaluated the area‐based terrain shading algorithm, Hillshade tool of ArcGIS, and the point‐specific shading algorithm from Solar Analyst (SA) in ArcGIS. Both algorithms showed shading overestimation, and Hillshade showed more accuracy with a mean absolute error (MAE) of 1.20%, as compared to the MAE of 1.66% of SA. The MAE of Hillshade increases exponentially as the spatial extent of the study area increases because the solar position for all locations on the surface is the same in Hillshade. Consequently, we suggest that the surface should be divided into more tiles in Hillshade when the discrepancy in the latitude of the whole surface is greater than 4°. Skyshed, which represents the horizon angle distribution in SA, is error‐prone over more complex terrain because horizon angle interpolation is problematic for such areas. We also propose a new terrain shading algorithm, with solar positions calculated using local latitude for each cell and the horizon angle calculated for every specific time interval, but without projections. The new model performs better than Hillshade and SA with an MAE of 0.55%. 相似文献
20.
针对主星带辅星群编队InSAR的双站、斜视、空间基线等特点，首先建立绝对测高误差与相对测高误差模型；重点分析了基线去相关对干涉相位误差的影响；对干涉车轮和钟摆编队的测高性能、对测高精度与基线矢量的关系进行仿真分析；其次与两种经典近似几何关系下的测高精度分析进行对比。仿真结果表明：干涉测高精度必须考虑基线去相关的影响；相对测高精度明显优于绝对测高精度；经典近似几何给分析测高精度带来很大误差。 相似文献