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统计数据是地图的重要补充数据,对常规统计专题地图来说,可视化表现手段和方法已比较成熟,但在处理差额较大数据时往往达不到比较理想的效果。通过对统计专题地图性质及用途的分析,研究和总结了适宜不同的制图要素和不同的用图对象的极差数据可视化表达的方法。 相似文献
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艾自兴 《武汉大学学报(信息科学版)》1986,11(4):14-22
本文基于用图案来组成图形符号的基本思想,引入图案拓扑等价的观点,较系统地对专题地图中点、线、面三类符号的绘制作了一些探讨。 相似文献
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GIS数据在专题地图可视化表达中的应用 总被引:1,自引:1,他引:0
以GIS数据与地图表达的关系为线索,结合林业规划制图过程,分析了GIS数据与地图表达的冲突,提出通过数据选择系统、分析与制图一体化策略及地图表现层次分类系统的构建来实现GIS数据与地图表达的融合,提高专题地图制图质量。 相似文献
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《制图学和地理信息科学》2013,40(2):105-118
Overlay (or heuristic) models have been shown to be a reasonable method to generate landslide susceptibility maps. However, overlay models are subjective and rely on expert judgment. The method developed here employs an overlay model but it tries to estimate certain parameters, such as slope angle or distance to streams, in a more quantitative manner. Each individual factor believed to have an influence on mass wasting processes is scaled to a value between 0 and 1. All different factors are then multiplied, producing the degree of stability, Df, which lies on a ratio scale, rather than a nominal or interval scale. Thus, a pseudo probability of failure can be obtained. The data required are derived partly from thematic maps and partly from stereo air photos. The air photo stereo pair is used to automatically derive a digital elevation model which is then used to create an orthoimage of an area. The air photos are also used to develop a land use map, an important component in estimating landslide susceptibility. This methodology was tested on a section of the Santa Monica Mountains near Malibu, California. The resulting map both visually and statistically appears to successfully identify problematic areas. Although the methodology was primarily developed to identify shallow slides, the crest of a large, deep-seated landslide was also recognized. The general methodology should be easily adaptable to other regions or could be applied with a different set of factors than those considered in this specific case. 相似文献
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分析了常规2维行程压缩算法存在的不足,在此基础上提出了一种在遍历栅格数据过程中直接快速动态生成2维行程的栅格数据压缩算法.该算法以MD码代替行列号来扫描栅格数据,对于一个2×2的窗口由MD码反解行列号只需转换左上角格网单元,同时以动态线性表代替静态线性表.在提取栅格单元的过程中,直接检测对比格网单元的属性值,动态分配内存来建立2维行程编码.最后,大量实验表明,算法在运行效率和内存占有量方面均优于常规的2维行程压缩算法. 相似文献
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实现栅格图形和图像数据矢量化提取的游程轮廓追踪法 总被引:12,自引:0,他引:12
提出一种直接利用栅格图形游程编码进行图斑边界多边形矢量化提取的有效方法。对遥感图像专题信息和栅格型地理空间分析结果的矢量化提取是GIS的重要手段 ,栅格数据结构可简化解决叠置分析等一类空间分析问题 ,其中需要高效矢量化技术的支撑。本方法充分利用栅格游程编码所具有的可操作性强、检索和转换便捷、隐含横向差异信息、可处理高精度和大规格图形和图像等特征 ,定义了“上邻游程”和“下邻游程” ,并采用相应有效查找算法和基于游程轮廓追踪的矢量化技术 ,使得计算机处理栅格数据矢量化的规模、精度和效率明显提高 ,可广泛应用于栅格型地理空间分析和遥感图像处理等方面。 相似文献
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《制图学和地理信息科学》2013,40(3):151-166
We present new methods for analyzing geo-referenced statistical data. These methods combine visualization and direct manipulation techniques of exploratory data analysis and algorithms for data mining. The methods have been implemented by integrating two hitherto separate software tools: Descartes for interactive thematic mapping, and the data mining toolbox Kepler. In using these tools, data analysis may proceed as a steady interaction between visual inspiration and insights gained from mathematical–statistical calculations. After introducing the various components of the methods and tools, the paper guides the reader through in-depth examples of using the tools in the context of analysis of urban demographic data. In particular, it is shown how geography-based classifications of urban districts can be related to available thematic characteristics by applying the data mining algorithms classification tree derivation, attribute weighting, and subgroup discovery. 相似文献
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费立凡 《武汉大学学报(信息科学版)》1983,8(1):87-101
本文着重讨论了栅格数据经自动预处理后,让电子计算机模拟人工制图综合,采用二维空间的曲率比较,寻找等高线上的特征点、筛选谷地点、跟踪谷底线、区分谷地重要性、量测谷间距、判断谷地的取舍,进而实现等高线谷地弯曲的成组概括等问题,同时给出了初步试验的结果。 相似文献
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基于二叉树的栅格数据快速编码及其实现 总被引:2,自引:0,他引:2
在对常规编码方法存在的不足进行分析的基础上,提出了在一次遍历栅格数据过程中生成线性二叉树的快速动态编码以及地程编码方法,该方法用堆栈的思想代替传统的线性表,以十进制orton码为顺序提取栅格单元数据并介入栈,以压栈的方式完成栅格单元或结点向上层的递归合并。当对整个栅格数据遍历一次后,栈中剩下的记录便是所需的线性二叉树编码结果。通过对算法的分析表明,该方法具有明显的优点和重要意义。 相似文献
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在分析栅格时空数据模型和栅格数据编码的基础上,提出了基于2维行程编码实现基态修正栅格时空数据模型的关键算法,包括对等分裂差异分析算法和快速差异累加算法.针对每个算法,分析了常规算法存在的不足,给出了改进算法的主要思想和详细步骤.最后,设计和开发了相应的实验系统,通过大量实验验证了算法的有效性,同时表明改进算法其运行效率和内存占有量方面均明显优于常规算法. 相似文献
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Abstract Grazing changes plant species composition of grassland ecosystems by selective removal and trampling. Grazing also alters soil physical and biogeochemical properties and can dramatically change hydrologic processes that can impact water budgets and quality. For these reasons, practical means are needed to assess grazing management practices and its impacts upon the land. This study examines whether a grazing intensity and range condition gradient can be detected in spectral reflectance characteristics of grasslands in northeastern Kansas. Multitemporal Landsat Thematic Mapper (TM) data, the normalized difference vegetation index (NDVI), and field data collected concurrent with the TM overpasses, were used in the analysis. Correlation analysis was used to examine relationships between spectral data and biophysical data. Next, the study sites within each grassland type were classified into three spectrally similar clusters. Grazing intensity, range condition, and biophysical characteristics were summarized for each spectral cluster and compared. The results suggest that NDVI may be used as a surrogate for living biomass for both grassland types and may be useful for predicting grazing intensity in native warm season grasslands. And while there appeared to be relationships between total living and non‐living cover, and TM NIR and MIR bands, there were no direct relationships between spectral characteristics and grazing intensity or range condition. 相似文献
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阐述了GPS观测数据质量的检核方法、原理及主要评价指标.介绍了TEQC和RTKLIB软件在数据质量分析方面的功能,利用实测GPS数据进行质量分析对比可得出:1) TEQC基于DOS环境运行,人机交互性差,RTKLIB软件运行于Windows系统,操作便捷;2) 二者数据质量的主要评价指标结果完全一致;3) RTKLIB软件可对卫星可见性、天空视图、DOP值进行图形化显示,但无电离层延迟误差、电离层延迟变化率和卫星方位角绘图功能;4) 将TEQC与RTKLIB软件结合可相互弥补,全面、直观地分析观测数据质量,达到很好的分析效果。 相似文献
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利用数据字典开发数字地形图质量检测软件 总被引:3,自引:0,他引:3
大比例尺数字地形图的质量检测方法是近年来同行们共同关注的热点。本文结合我院实施南京市1:500、1:1000地形图GIS建库工作实践,介绍我院SCS2000平台大比例尺数字地形图质量检测软件的功能,并重点阐述了由本人编写,利用数据字典进行数据质量检测软件的开发思路及应用。 相似文献
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房屋建筑是地理国情普查的重要要素之一。在实际生产工作中,由于高分辨率遥感影像受成像条件影响大以及人眼认知的局限,很难通过目视解译准确判读房屋建筑的边界、层高和密度等属性。此外,地理国情普查工作量大,重复性工作多,给地理国情普查工作带来一定困难。针对以上问题,以Arc GIS和Python为开发和应用环境,从现势性较好的1∶2 000地形图上批量提取房屋建筑专题数据,服务于地理国情普查工作。 相似文献