激光扫描多三维视图的全自动无缝镶嵌

探讨了不同坐标系下的三维点云统一到某一固定坐标系下形成完整目标的问题,提出了一种全自动获取三维视图配准初值的方法。对多三维视图,应用基于闭合条件的整体平差模型,获得最小二乘意义下的最优变换参数,实现了对多三维视图的全自动无缝镶嵌。利用激光扫描仪的实际扫描数据进行了试验,得到了预期的结果,并验证了本文方法的可行性和有效性。     

地震波面波空间相干性规律研究

本文选取台湾LSST、SMART-1台阵地震记录,分别计算不同间距S波和面波相干系数,采用Loh提出的相干函数模型对计算结果进行参数拟合。研究结果表明,当台站间距$ d < \text{50}\;{\rm{m}} $时,面波和S波相干系数基本相同;当台站间距$d = \text{500}\;{\rm{m}}$时,面波相干系数小于S波相干系数,且随着台站间距的增大,二者的差别逐渐增大;当台站间距$ d > \text{500}\;{\rm{m}}$时,面波空间相干性几乎不存在,可不考虑。本文给出的面波相干函数模型参数可作为大型盆地中的长大结构抗震分析时合成地震动场的参考。     

背包、车载激光扫描结合无人机倾斜航测实践于社区全息数据采集

随着测绘地理信息使用需求的变化及测绘数据获取技术的进步,全息测绘成为新型基础测绘数据生产的一种思路.SLAM背包结合车载激光扫描系统以其灵活、全时、室内外一体、高精度及全息采集的方式,在地面及内部信息的获取中具有效率高、信息全的特点.与无人机倾斜航测相结合采集目标的全景三维信息,融合处理后可获得测区的全息数据,能为社区...     

Simulating the spatial diffusion of memes on social media networks

This article reports the findings from simulating the spatial diffusion processes of memes over social media networks by using the approach of agent-based modeling. Different from other studies, this article examines how space and distance affect the diffusion of memes. Simulations were carried out to emulate and to allow assessment of the different levels of efficiency that memes spread spatially and temporally. Analyzed network structures include random networks and preferential attachment networks. Simulated spatial processes for meme diffusion include independent cascade models and linear threshold models. Both simulated and real-world social networks were used in the analysis. Findings indicate that the numbers of information sources and opinion leaders affect the processes of meme diffusion. In addition, geography is still important in the processes of spatial diffusion of memes over social media networks.     

A Review of: Environmental Modelling with GIS.

Cartographic modelling operations provide powerful tools for analysing and manipulating geographic data in the raster data model. This research extends these operations to the vector data model. It first discusses how the spatial scopes of analysis can be defined for point, line, and polygon features analogous to the raster cell. Then it introduces the local, focal, and zonal operations available for vector features, followed by providing a prototype syntax that might guide the implementation of these operations. Through example applications, this research also demonstrates the usefulness of these operations by comparing them with traditional vector spatial analysis.     

Using GIS to analyse a severe forest blowdown in the Southern Rocky Mountains

Many studies have helped us understand where blowdowns occur, how forests regenerate and respond to large disturbances. However, few studies have analysed how physical and biological factors affect blowdowns or interact with one another to determine susceptibility to blowdown. These factors range from the natural physical setting to past disturbances, and human-related features, such as roads and timber harvest units. These factors were examined in this study. Patches of the blown-down forest were mapped for the 1997 Routt-Divide blowdown, which affected over 10 000 ha of subalpine forest in north-central Colorado. A systematic sampling scheme was used to extract information on predictors for sampling points inside and outside the blowdown. Data on predictors were used in Classification and Regression Trees (CART) and logistic regression to model blowdown occurrence and severity. Two models were applied, and both were able to predict with an overall success rate of 75% or more. These two models produced similar results, showing that the Routt-Divide blowdown was most influenced by factors pertaining to the physical setting: distance to the Continental Divide, wind exposure, elevation, aspect, and cover type. Surprisingly, soil permeability and water-holding capacity and distance to natural edges (e.g. forest-meadow) were not correlated significantly with the blowdown pattern.     

Testing the effects of positional uncertainty on spatial decision‐making

There is now increasing agreement that the uncertainty associated with spatial information should be represented to users in a manner that is comprehensive and unambiguous. To assist with this task, researchers have developed a variety of methods to portray spatial uncertainty. While there has been some testing of the effectiveness of these displays, the possible effects of such representations on decision‐making have not yet been thoroughly investigated. Indeed, studies from the psychological literature indicate that people do not always make the same decisions when presented with the same information, and they can also be sensitive to the effects of presentation, task, and context. This paper examines how the use of four different methods to represent positional uncertainty can affect spatial decision‐making. The authors found that extremely significant differences in participants' responses were exhibited, depending on the manner in which positional uncertainty was displayed, although little difference was observed in the ability of the participants to comprehend the four display methods. In addition, strong preferences were recorded for certain representations over others.     

Remotely sensing the spatial and temporal land cover changes in Eastern Mau forest reserve and Lake Nakuru drainage basin,Kenya

This study aimed at characterizing land cover dynamics for four decades in Eastern Mau forest and Lake Nakuru basin, Kenya. The specific objectives were to: (i) identify and map the major land cover types in 1973, 1985, 2000 and 2011; (ii) detect and determine the magnitude, rates and nature of the land cover changes that had occurred between these dates, and; (iii) establish the spatial and temporal distribution of these changes. Land cover types were discriminated through partitioning, hybrid classification and spatial reclassification of multi-temporal Landsat imagery. The land cover products were then validated and overlaid in post-classification comparison to detect the changes between 1973 and 2011. The accuracies of the land cover maps for 1973, 1985, 2000 and 2011 were 88%, 95%, 80% and 89% respectively. Six land cover classes, namely forests-shrublands, grasslands, croplands, built-up lands, bare lands and water bodies, were mapped. Forests-shrublands dominated in 1973, 1985 and 2000 covering about 1067 km², 893 km² and 797 km² respectively, but were surpassed by croplands (953 km²) in 2011. Bare lands occupied the least area that varied between 2 km² and 7 km² during this period. Overall, forests-shrublands and grasslands decreased by 428 km² and 258 km² at the annual average rates of 1% each, whereas croplands and built-up lands expanded by 660 km² and 24 km² at the annual rates of 6% and 16% respectively. The key hotspots of these changes were distributed in all directions of the study area, but at different times. Therefore, policies that integrate restoration and conservation of natural ecosystems with enhancement of agricultural productivity are strongly recommended. This will ensure environmental sustainability and socio-economic well-being in the area. Future research needs to assess the impacts of the land cover changes on ecosystem services and to project the future patterns of land cover changes.     

Mapping the popularity of urban restaurants using social media data

Nowadays, geographers show growing interest in providing location-based services for urban residents. It is of great practical significance to screen and recommend the most popular restaurants to consumers, as dining is important to every urban dweller. Consumer review website (CRW) has emerged as an active social media platform in catering industry. This paper demonstrated how to quantify the popularity of urban restaurants (PUR) by using CRW, namely, Dianping.com. An applied popularity index (PI) was developed to quantify PUR, based on the consumer review scores (food, service, and decoration) and physical data (evaluation frequency and restaurant grade) for 8259 restaurants within the Hangzhou city, China. All the information, together with the geographic location data, was harvested from the corresponding Application Programming Interface (API) platform. PUR was then mapped by using a geographic information system (GIS). Results showed that restaurants of high popularity were generally concentrated in old urban districts, whereas those in new urban districts presented low popularity. The kernel density distribution of PI also highlighted the geography that the PI values declined from the central city toward the outskirts. Locational associations between PUR and urban functional units (bank, shopping mall, school, cinema, hotel, bar, and scenic spot) generally presented a similar tendency. Restaurants with high PI values were in high proximity to urban functional units, whereas those with low PI values were located far away from other functional units. It implied that restaurants with high popularity tended to be located in high mixture with urban functional units. Although we used Dianping.com to perform the analysis, the presented methodology can be extended to other types of CRWs. Our study is believed to provide new insights into applied geographic sciences.     

华南暖区暴雨事件的筛选与分类研究

利用逐小时降水资料,采用客观方法对1982~2015年华南地区暖区暴雨进行了筛选和分类研究。主要结果如下:华南区域暖区暴雨事件共计177例,暖区暴雨占筛选的暴雨事件的16.86%,表明暖区暴雨是华南非常重要的降水过程。暖区暴雨主要出现在4~7月,6月份最多,平均持续11.58 h。暖区暴雨事件发生位置主要集中在广东、广西的沿海地区和粤北山区,有四个降雨中心。产生华南暖区暴雨的天气形势主要有四类,切变线型、低涡型、南风型和回流型,不同类型的暖区暴雨对华南地区的内陆和沿海的作用不同,且南风影响下的暖区暴雨发生频率较高,影响较大,是一类较为重要的暖区暴雨。