共查询到20条相似文献，搜索用时 31 毫秒
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矢量空间数据的可用性取决于其空间位置不确定性,直接受控于点元位置误差的二维空间概率分布模式。应用GPS RTK技术,对选定测量点的空间位置进行重复观测,累积观测20 d,采用一维、二维正态分布检验与数学模型拟合3种分析方法,研究了GPS RTK测点误差空间概率分布模式。结果表明,GPS RTK测点误差空间分布呈现为具有一定方向的二维正态分布形式,并且这种分布形式的显著性随着点元位置观测时间的缩短而不断提升。所得到的GPS RTK测点误差空间概率分布模式可为其测点误差空间分布影响因素分析与数学预测模型构建奠定基础,并有助于推动矢量空间数据位置不确定性的理论研究。 相似文献
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《制图学和地理信息科学》2013,40(4):196-205
Visualization of reliability in spatial data has been the subject of considerable recent research activity. Animation has been suggested as one method to achieve this, and its application to various measures associated with class-area maps (classified satellite images and soil maps) has been discussed elsewhere. Animation is achieved by randomly selecting a location and then assigning it to a different map unit (cover or soil type) according to the information on the reliability associated with the original map or map units. In this article the same basic method is extended to mapping locational reliability in dot maps and surface error in a digital elevation model (DEM). In the former case, the dots, which are randomly located in the first place, are randomly relocated so that any meaningless positional information implicit in the location of the dots is lost while the meaningful information (the number of dots within a region) remains constant. In the DEM, animation uses a random field as an error surface, based upon the root mean squared error (RMSE). The amount of error at a location is constantly changed, giving no impression that the elevation is precisely known. The ability to vary the spatial autocorrelation within the error field provides a graphic illustration that the usual RMSE is not a sufficient method for the reporting of error in spatial databases. In both examples animation of reliability is believed to make a novel, but appropriate, use of the computer in cartography. 相似文献
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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
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Impacts of Positional Error on Spatial Regression Analysis: A Case Study of Address Locations in Syracuse, New York 总被引：1，自引：0，他引：1
Daniel A Griffith Marco Millones Matthew Vincent David L Johnson Andrew Hunt 《Transactions in GIS》2007,11(5):655-679
Positional error is the error produced by the discrepancy between reference and recorded locations. In urban landscapes, locations typically are obtained from global positioning systems or geocoding software. Although these technologies have improved the locational accuracy of georeferenced data, they are not error free. This error affects results of any spatial statistical analysis performed with a georeferenced dataset. In this paper we discuss the properties of positional error in an address matching exercise and the allocation of point locations to census geography units. We focus on the error's spatial structure, and more particularly on impacts of error propagation in spatial regression analysis. For this purpose we use two geocoding sources, we briefly describe the magnitude and the nature of their discrepancies, and we evaluate the consequences that this type of locational error has on a spatial regression analysis of pediatric blood lead data for Syracuse, NY. Our findings include: (1) the confirmation of the recurrence of spatial clustering in positional error at various geographic resolutions; and, (2) the identification of a noticeable but not shockingly large impact from positional error propagation in spatial auto‐binomial regression analysis results for the dataset analyzed. 相似文献
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Andrew S. Foy Laurence W. Carstensen Stephen P. Prisley James B. Campbell Randel L. Dymond 《Transactions in GIS》2015,19(4):604-618
Advances in computer technologies have improved the quality of maps, making map comparison and analysis easier, but uncertainty and error still exist in GIS when overlaying geographic data with multiple or unknown confidence levels. The goals of this research are to review current geospatial uncertainty literature, present the Error‐Band Geometry Model (EBGM) for classifying the size and shape of spatial confidence intervals for vector GIS data, and to analyze the interpretability of the model by looking at how people use metadata to classify the uncertainty of geographic objects. The results from this research are positive and provide important insight into how people interpret maps and geographic data. They suggest that uncertainty is more easily interpreted for well defined point data and GPS data. When data is poorly defined, people are unable to determine an approach to model uncertainty and generate error‐bands. There is potential for using the EBGM to aid in the development of a GIS tool that can help individuals parameterize and model spatial confidence intervals, but more research is needed to refine the process by which people use the decision tree. A series of guiding questions or an “uncertainty wizard” tool that helps one select an uncertainty modeling approach might improve the way people apply this model to real‐world applications. 相似文献
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针对类型地图,在介绍已有空间相关关系分析方法的基础上,给出一种计算空间相关关系的简便方法,其基本思想是用现实分布与随机分布下相对重叠度的差异来表达类型之间的相关程度;同时还讨论了位置不确定性对类型地图空间相关关系的影响.实验表明,该方法能够有效表达类型地图之间的整体空间相关和局部空间相关. 相似文献
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《制图学和地理信息科学》2013,40(1):42-50
Geographic Information Systems (GIS) algorithms are used to simplify, edge match, and overlay large data sets. Some of these GIS processes can cause considerable positional changes to spatial data which are sometimes difficult to assess. This study presents a visualization technique for the evaluation of GIS algorithms and their positional effects on spatial data. The technique is applicable to vector representations and can be used with any GIS operation that changes vector geometry. The technique employs a uniform reference grid to exploit the visual skills of human operators in the evaluation of positional changes in spatial databases after applying GIS transformations. Changes in grid cell length, area, and shape, along with a set of displacement vectors, can be analyzed to evaluate positional changes in spatial data and to compare the behaviors of different algorithms. The technique can assist GIS users in the documentation of positional changes and in the comparison and selection of algorithms for various mapping tasks. Such a technique may assist software developers in creating and selecting appropriate GIS algorithms. 相似文献
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Jayanta Kumar Ghosh Abhishek Dubey 《Journal of the Indian Society of Remote Sensing》2009,37(2):215-221
With the declaration of India’s new map policy (NMP), user community is looking towards its impact on spatial accuracy of
GIS theme maps arising out of transformation from existing system (Polyconic Projection on Everest 1830 spheroid datum) to
Open series maps (OSM in UTM projection on WGS 84 ellipsoid) and vice versa. This results in registration error of existing
maps with new maps. This study aims at finding out the impact of transformation on the spatial location and to determine the
extent to which the existing theme layers can be used along with the new series maps without losing accuracy. Results show
that there are some geographic regions in India whose GIS database can be used as it is available, depending on the scale
and within the acceptable positional accuracy. For other region, depending on the scale of theme layers, a detail analysis
of the situation will be required depending on project requirements. 相似文献
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矢量GIS平面一般曲线等概率密度误差模型 总被引：1，自引：0，他引：1
基于数值分析、经典概率论和线状实体误差分布机理，定义了矢量GIS平面一般曲线等概率密度误差模型的概念，提出了平面一般曲线等概率密度误差模型尺度因子的概念和确定方法，姑合平面一般曲线落入其相应等概率密度误差模型内的概率算法和概率置信水平，确定了尺度因子的具体数值，给出了平面一般曲线等概率密度误差模型的形状与规模。 相似文献
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《The Cartographic journal》2013,50(1):21-26
AbstractThe spatially discontinuous choropleth map is a poor representation of the underlying continuous distribution of population density. A possible alternative is to derive dasymetric maps at a fine spatial resolution by making use of satellite imagery in a geographical information system. However, there are cartographic problems when these maps are displayed and further processing is needed in order to obtain approximations to a continuous density surface. Isarithmic maps of these density surfaces retain a high degree of spatial accuracy while providing pleasing and highly adaptable presentations.The methods used to generate dasymetric and isarithmic maps are readily implemented in most raster based geographical information systems. For example, the classification of remotely sensed imagery, the subsequent processing and integration of data, and most of the cartographic display, were all undertaken in this work using the low cost IDRISI GIS that operates on standard IBM PC compatible hardware. 相似文献
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An Adaptive Method of High Accuracy Surface Modeling and Its Application to Simulating Elevation Surfaces 总被引：3，自引：0，他引：3
An adaptive method is employed to speed up computation of high accuracy surface modeling (HASM), for which an error indicator and an error estimator are developed. Root mean‐square error (RMSE) is used as the error estimator that is formulated as a function of gully density and grid cell size. The error indicator is developed on the basis of error surfaces for different spatial resolutions, which are interpolated in terms of the absolute errors calculated at sampled points while paying attention to the landform characteristics. The error surfaces indicate the magnitude and distribution of errors in each step of adaptive refinement and make spatial changes to the errors in the simulation process visualized. The adaptive method of high accuracy surface modeling (HASM‐AM) is applied to simulating elevation surface of the Dong‐Zhi tableland with 27.24 million pixels at a spatial resolution of 10 m × 10 m. Test results show that HASM‐AM has greatly speeded up computation by avoiding unnecessary calculations and saving memory. In addition, HASM‐AM improves simulation accuracy. 相似文献
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由于线元上任一点坐标的误差不仅受端点误差的影响,还会受到长度误差的影响,故不确定性模型要考虑各种影响位置精度的参数误差,对3维空间直线不确定性模型作了进一步研究.不但考虑了端点误差的影响,还顾及了长度误差的影响,使模型在理论上更为严密.理论和实验研究表明,长度误差影响了直线方向的精度. 相似文献
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对8个不同地区对应的同一时间的ETM+数据和MODIS数据,利用谱间关系法得到30 m和250 m分辨率具有不同景观格局分布的水体专题图,研究分辨率对不同景观格局分布的水体提取的影响。通过比较发现,区域内水体边缘密度很小时,ETM+和MODIS提取结果的误差很小;当区域内水体边缘密度很大时,ETM+和MODIS提取结果的误差相应就变大。通过引入景观格局指数与两种分辨率的提取结果进行回归分析发现,对于不破碎区域的水体,MODIS和ETM+可以得到相近的精度;而对于中度破碎的水体,引入景观格局指数信息能显著地提高中度破碎水体的精度;但对于高度破碎的水体,通过引入景观格局指数信息的多元回归几乎不能提高精度。 相似文献
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T. G. Nefedova 《地理信息系统科学与遥感》2013,50(4):256-273
The principles of systems mapping are employed in a model simulating the effects of human activity on the environment. The model takes the form of series of maps which are organized within three basic units or “blocks.” Block I contains general preliminary maps of land use and environmental change within an area which can serve as a basis for subsequent forecasting and proposals for improving land use. Block II contains maps that take stock of, evaluate, and predict human impacts on specific environmental components, and show the spatial distribution of measures proposed to ameliorate these impacts. Block III consists of maps synthesizing the component-related information of the preceding block for the purpose of providing summary assessments about the condition of the environment and land use conflicts in an area and targeting areas deserving the most comprehensive reclamation efforts. Methods of compiling the various maps are described in detail. Translated from: Izvestiya AN SSSR, seriya geograficheskaya, 1986, No. 2, pp. 114–127. 相似文献
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There has been a great deal of research about errors in geographic information and how they affect spatial analyses. A typical GIS process introduces various types of errors at different stages, and such errors usually propagate into errors in the result of a spatial analysis. However, most studies consider only a single error type thus preventing the understanding of the interaction and relative contributions of different types of errors. We focus on the level of detail (LOD) and positional error, and perform a multiple error propagation analysis combining both types of error. We experiment with three spatial analyses (computing gross volume, envelope area, and solar irradiation of buildings) performed with procedurally generated 3D city models to decouple and demonstrate the magnitude of the two types of error, and to show how they individually and jointly propagate to the output of the employed spatial analysis. The most notable result is that in the considered spatial analyses the positional error has a much higher impact than the LOD. As a consequence, we suggest that it is pointless to acquire geoinformation of a fine LOD if the acquisition method is not accurate, and instead we advise focusing on the accuracy of the data. 相似文献