Quantifying the spatial heterogeneity of points     

Hua Shu  Ci Song  Ting Ma  Yunyan Du  Zide Fan 《International journal of geographical information science》2019,33(7):1355-1376

Variation in the spatial heterogeneity of points reflects the evolutionary process or mechanism of geographical events. The key to depicting this variation is quantifying spatial heterogeneity. In this paper, the spatial heterogeneity of a point pattern is defined as the degree of aggregation-type deviation from complete spatial randomness. In such a case, a goodness-of-fit-type statistic based on the distribution of nearest-neighbor distances called the level of heterogeneity (LH*) is regarded as a standard measurement, and a normalized version called the normalized level of heterogeneity (NLH*) is proposed for datasets with different point numbers and study region areas. Considering the complex integration calculation of LH* and NLH*, simulation experiments are implemented to test the capability of some classic nearest-neighbor statistics in quantifying spatial heterogeneity. The results showed that except for the standard LH* statistic, only Clark and Evans’ statistic (A-w) and Byth and Ripley’s statistic (H-xw) are robust. Statistics NLH*, (A-w) and (H-xw) are validated by quantifying the spatial heterogeneity of two-dimensional crime events, three-dimensional earthquake events and four-dimensional origin-destination (OD) events. The results indicate that these statistics all have a reasonable explanation in quantifying spatial heterogeneity for real-world geographical events of different types and with different dimensions. Compared with NLH*, Clark and Evans’ (A-w) statistic and Byth and Ripley’s (H-xw) statistic are recommended from the perspective of accessibility.  相似文献   

Waveform-based point cloud classification in land-cover identification     

《International Journal of Applied Earth Observation and Geoinformation》2015

Full-waveform topographic LiDAR data provide more detailed information about objects along the path of a laser pulse than discrete-return (echo) topographic LiDAR data. Full-waveform topographic LiDAR data consist of a succession of cross-section profiles of landscapes and each waveform can be decomposed into a sum of echoes. The echo number reveals critical information in classifying land cover types. Most land covers contain one echo, whereas topographic LiDAR data in trees and roof edges contained multi-echo waveform features. To identify land-cover types, waveform-based classifier was integrated single-echo and multi-echo classifiers for point cloud classification.The experimental area was the Namasha district of Southern Taiwan, and the land-cover objects were categorized as roads, trees (canopy), grass (grass and crop), bare (bare ground), and buildings (buildings and roof edges). Waveform features were analyzed with respect to the single- and multi-echo laser-path samples, and the critical waveform features were selected according to the Bhattacharyya distance. Next, waveform-based classifiers were performed using support vector machine (SVM) with the local, spatial features of waveform topographic LiDAR information, and optical image information. Results showed that by using fused waveform and optical information, the waveform-based classifiers achieved the highest overall accuracy in identifying land-cover point clouds among the models, especially when compared to an echo-based classifier.  相似文献   

基于精密单点定位的岛礁控制测量研究     

洪泽  王国举 《全球定位系统》2015,(3):51-54

本文利用静态精密单点定位技术解算海岛礁控制点的位置坐标,并利用高精度长基线解算软件GAMIT／GLOBK的结果作对比,结果显示其精度可达到厘米级别。在数据解算过程中分析影响误差的主要来源,并重点讨论了多路径效应对精度的影响,提出相关的处理手段,最终达到提高精度的目的。  相似文献   

广州市多类型商业中心识别与空间模式   总被引：3，自引：5，他引：3  

吴康敏  张虹鸥  王洋  吴旗韬  叶玉瑶 《地理科学进展》2016,35(8):963-974

不同职能类型商业中心识别对研究城市商业空间结构有重要意义。与传统识别方法相比,大数据的分析更为精确和便捷。本文以广州市核心区59125条城市热点(POI)数据为基础,利用核密度分析、统计分析、最邻近距离分析等方法识别广州市多类型商业中心的边界,探索其商业空间结构与模式。结果表明：①广州市商业结构呈现明显双核集聚式分布,传统的越秀分区与现代的天河分区构成当前广州市商业空间的双中心;②不同类型的商业中心在空间上呈现显著分异,其中城市生活与公共服务中心在越秀区,商务与金融中心在天河区,休闲娱乐中心呈现分散集聚式特征;③广州市商业结构的空间模式是“圈层+组团”式分布,其中,生活、公共服务、商务职能集中分布于内圈层,娱乐休闲职能呈组团状镶嵌于各圈层中。  相似文献   

GPS���ܵ��㶨λ�������������о�   总被引：3，自引：2，他引：1  

郝明  王庆良  崔笃信 《大地测量与地球动力学》2009,29(2):88-91

???????????λ????????????÷???????: 1)???????????????????δ???????????Э?????????; 2)?????????????????????????С?????????, ?????????IGS???????17С????????????????????????λ?????????????, ?????·???????λ?????????????????????????????????, ?????????Ч?????  相似文献   

利用VB开发的MAPGIS明码数据格式文件生成系统     

钟华 《江苏地质》2001,25(3):166-169

MAPGIS目前还没有提供直接由坐标数据输入成图的功能.利用VB开发的一个直接使用现成数据源生成MAPGIS的明码数据格式文件的系统,使得将现有数据加载到相关的地形、地质、物探等成果图件上的操作变得简单和十分方便.论述了系统的开发思路和主要特点.  相似文献   

陀螺经纬仪定向精度分析     

高福聚 《测绘工程》1995,(3)

通过应用WILD GAK-1陀螺经纬仪进行逆转点法、中天法及时差法的定向实验,论述了3种定向方法的理论精度,并和实际定向精度进行了比较。  相似文献   

非线性伪双曲方程的第二初边值问题     

任留成 《测绘学院学报》1995,(4)

本文利用Ｌｅｒａｙ－Ｓｃｈａｕｄｅｒ不动点原理和Ｓｏｂｏｌｅｖ估计，证明了非线性伪双曲方程的第二初边值问题整体弱解的存在唯一性，其中ｍ≥１，ａｉ＞０（ｉ＝１，２，３）都是常数。  相似文献   

GIS基础空间关系分析   总被引：5，自引：0，他引：5  

蔡少华  翟战强 《测绘工程》1999,8(2):38-42

在点集拓扑学基础上,分析了空间关系的基本类型－拓扑关系、方向关系、度量关系,并对各关系的基本划分与识别规则进行了详细描述。  相似文献   

点源大气扩散模式计算的参数选取     

邓新民 《成都信息工程学院学报》1999,(2):3

就实际环评工作中点源大气扩散模式计算参数选取的有关问题提出了一些新的看法。  相似文献