DCAD: a dual clustering algorithm for distributed spatial databases

Spatial objects have two types of attributes: geometrical attributes and non-geometrical attributes, which belong to two different attribute domains (geometrical and non-geometrical domains). Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clustering: local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted. Second, local features from each site are sent to a central site where global clustering is obtained based on those features. Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.     

DCAD： a Dual Clustering Algorithm for Distributed Spatial Databases

Spatial objects have two types of attributes: geometrical attributes and non-geometrical attributes, which belong to two different attribute domains (geometrical and non-geometrical domains). Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clus- tering: local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted. Second, local features from each site are sent to a central site where global clustering is obtained based on those features. Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.     

Spatio-temporal analysis of industrial composition with IVIID: an interactive visual analytics interface for industrial diversity

The industrial composition of places has received considerable attention because of the widespread belief that industrial diversity buffers regional economies from economic shocks. Subsequently, a variety of toolkits and indices have been developed with the goal of better capturing the compositional dynamics of regions. Although useful, a key drawback of these indices is their static nature, which limits the utility of these indices in a space–time context. This paper provides an overview of and applications of an interface called interactive visualization tool for indices of industrial diversity, which is a visual analytics tool developed specifically for the analysis and visualization of local measures of industrial composition for areal data. This overview will include a discussion of its key features, as well as a demonstration of the utility of the interface in exploring questions surrounding diversity and the dynamic nature of composition through space and time. A focus of this demonstration is to highlight how the interactivity and query functionality of this interface overcome several of the obstacles to understanding composition through space and time that prior toolkits and comparative static approaches have been unable to address.     

Mental maps and travel behaviour: meanings and models

In this paper, the “mental map” concept is positioned with regard to individual travel behaviour to start with. Based on Ogden and Richards’ triangle of meaning (The meaning of meaning: a study of the influence of language upon thought and of the science of symbolism. International library of psychology, philosophy and scientific method. Routledge and Kegan Paul, London, 1966) distinct thoughts, referents and symbols originating from different scientific disciplines are identified and explained in order to clear up the notion’s fuzziness. Next, the use of this concept in two major areas of research relevant to travel demand modelling is indicated and discussed in detail: spatial cognition and decision-making. The relevance of these constructs to understand and model individual travel behaviour is explained and current research efforts to implement these concepts in travel demand models are addressed. Furthermore, these mental map notions are specified in two types of computational models, i.e. a Bayesian Inference Network (BIN) and a Fuzzy Cognitive Map (FCM). Both models are explained, and a numerical and a real-life example are provided. Both approaches yield a detailed quantitative representation of the mental map of decision-making problems in travel behaviour.     

Continuity markers as an aid for children in finding the peripheral continuity of world maps

ABSTRACT

Many map readers, including both children and adults, find it difficult to determine where they would be located along the edge of a world map after crossing that edge. Different types of markers have long been drawn close to the map’s edge – for example, in an atlas – to help map readers identify the map upon which they will find themselves if that edge is passed. In this study, a method similar to that used to show the continuity between maps in an atlas has been tested to determine whether continuity markers can also be used to help map readers find a world map’s actual peripheral continuity. The study involved children between the ages of 10 and 13 years and showed that continuity markers do help children determine the map’s actual peripheral continuity, in combination with a lesson that describes how to find the actual peripheral continuity of a world map. This article, therefore, concludes that continuity markers for world maps can be a useful part of map design that clarifies how the edges of a world map fit together for children who have learned to use this tool.     

Web-based terrain and vector maps visualization for Wenchuan earthquake

This paper presents a Web-based three-dimensional Geographic Information System (3DGIS) for Wenchuan earthquake disaster assessment. With the help of information technology resources, geoscientists are in a position to learn more about the structure of the earthquake in efficient ways. Due to huge spatial datasets of Wenchuan, China and narrow network bandwidth, general-purpose applications are difficult to transmit and visualize these datasets on the network. The application aims to interactively represent and transfer large spatial objects of Wenchuan County, China, as well as for dynamically rendering them in networking environments. Level-of-detail (LOD) terrain models and vector maps are created, and the server–client architecture is presented. The application provides an effective way for powerful access and manipulation of large-scale Wenchuan datasets.     

航空遥感稳定平台的模型参考自适应控制

针对航空遥感惯性稳定平台中所受到的不平衡力矩等所引起的成像载荷不稳定导致无法获取高分辨率遥感数据的问题,提出了在平台控制系统中应用基于模型参考的自适应比例-积分-微分控制方法。根据需求设计出参考模型,将参考系统输出与实际系统输出之间的误差输入到自适应PID调节器,实时调整PID参数,对误差进行实时校正,以达到抑制不平衡力矩扰动、提高稳定平台稳定精度的目的。对所提出的模型参考自适应控制方法进行了仿真验证,结果表明:相对传统PID方法,模型参考自适应控制器对偏心力矩等主要干扰具有很好的抑制作用,系统输出能够很好地跟踪姿态变化,系统稳定精度得到显著提高。     

Downscaling Landsat-8 land surface temperature maps in diverse urban landscapes using multivariate adaptive regression splines and very high resolution auxiliary data

ABSTRACT

We propose a method for spatial downscaling of Landsat 8-derived LST maps from 100(30?m) resolution down to 2–4?m with the use of the Multiple Adaptive Regression Splines (MARS) models coupled with very high resolution auxiliary data derived from hyperspectral aerial imagery and large-scale topographic maps. We applied the method to four Landsat 8 scenes, two collected in summer and two in winter, for three British towns collectively representing a variety of urban form. We used several spectral indices as well as fractional coverage of water and paved surfaces as LST predictors, and applied a novel method for the correction of temporal mismatch between spectral indices derived from aerial and satellite imagery captured at different dates, allowing for the application of the downscaling method for multiple dates without the need for repeating the aerial survey. Our results suggest that the method performed well for the summer dates, achieving RMSE of 1.40–1.83?K prior to and 0.76–1.21?K after correction for residuals. We conclude that the MARS models, by addressing the non-linear relationship of LST at coarse and fine spatial resolutions, can be successfully applied to produce high resolution LST maps suitable for studies of urban thermal environment at local scales.     

Interactive maps for visual exploration of grid and vector geodata

This article considers two types of tools used for the analysis of spatial data: computational tools for grid data and visualization-based interactive exploratory techniques. The main purpose is to demonstrate that computational and visual techniques are complementary, and their combined use in data analysis may produce a synergistic effect. To this end, we describe two example scenarios of data analysis in the evaluation of potential damage from earthquakes and in analysis of forest resources. The analyses were performed with the use of CommonGIS, featuring the availability of powerful geocomputational tools and interactive visualization-related facilities that can be efficiently used in combination in a desktop environment or via the World Wide Web.     

Comparison of basin morphometry derived from topographic maps,ASTER and SRTM DEMs: an example from Kerala,India

The drainage network of a sixth-order tropical river basin, viz. Ithikkara river basin, was extracted from different sources such as Survey of India topographic maps (1: 50,000; TOPO) and digital elevation data of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) (30 m) and Shuttle Radar Topography Mapping Mission (SRTM) (90 m). Basin morphometric attributes were estimated to evaluate the accuracy of the digital elevation model (DEM)-derived drainage networks for hydrologic applications as well as terrain characterization. The stream networks derived from ASTER and SRTM DEMs show significant agreement (with slight overestimation of lower order streams) with that of TOPO. The study suggests that SRTM (despite the coarser spatial resolution) provides better results, in drainage delineation and basin morphometry, compared to ASTER. Further, the variability of basin morphometry among the data sources might be attributed to spatial variation of elevation, raster grid size and vertical accuracy of the DEMs as well as incapability of the surface hydrologic analysis functions in the GIS platform.     

Remote sensing-derived national land cover land use maps: a comparison for Malawi

Reliable land cover land use (LCLU) information, and change over time, is important for Green House Gas (GHG) reporting for climate change documentation. Four different organizations have independently created LCLU maps from 2010 satellite imagery for Malawi for GHG reporting. This analysis compares the procedures and results for those four activities. Four different classification methods were employed; traditional visual interpretation, segmentation and visual labelling, digital clustering with visual identification and supervised signature extraction with application of a decision rule followed by analyst editing. One effort did not report classification accuracy and the other three had very similar and excellent overall thematic accuracies ranging from 85 to 89%. However, despite these high thematic accuracies there were very significant differences in results. National percentages for forest ranged from 18.2 to 28.7% and cropland from 40.5 to 53.7%. These significant differences are concerns for both remote-sensing scientists and decision-makers in Malawi.     

一种自适应快速曝光控制方法

针对在快速运动中连续高速地获取高质量的图像信息,提出了一种基于光圈优先的自动曝光控制方法。通过对初始图像的评估,确定当前景物亮度下最佳光圈大小,进而获得此光圈下不同景物亮度的曝光时间,由此建立景物亮度与曝光时间的关系模型。在实际运用中根据关系模型,通过跟踪当前景物亮度动态调整曝光时间以达到获取最佳曝光量的目的。该方法具有实时、快速、成像质量高和控制精确可靠的特点,并在实际应用中得到验证。     

一种基于HVS和自适应小波变换的彩色图像水印算法

数字水印技术是实现数字产品产权保护的一种新方法。本文提出了一种基于HVS和自适应小波变换的彩色图像水印改进算法。首先利用改进的自适应小波变换对原始图像进行处理,然后采用混合置乱算法对水印图像进行处理。同时根据HVS的特点来确定水印的嵌入强度。实验证明这种算法具有较好的隐蔽性,对各种图像处理操作是鲁棒的。     

城市多种地图一体化综合测绘模式分析与研究

基于"数字城市"和城市地理信息系统基本建设的要求,对现有城市测绘体系进行分析,根据城市各项测绘技术工作特点,探讨城市多种地图一体化综合测绘的现实意义和可行性,初步提出城市多种地图一体化综合测绘的内容和部分技术指标,并通过实例进行应用检验。     

Developing spatially and thematically detailed backdated maps for land cover studies

ABSTRACT

Global or regional land cover change on a decadal time scale can be studied at a high level of detail using the availability of remote sensing data such as that provided by Landsat. However, there are three main technical challenges in this goal. First, the generation of land cover maps without reference data is problematic (backdating). Second, it is important to maintain high accuracies in land cover change map products, requiring a reasonably rich legend within each map. Third, a high level of automation is necessary to aid the management of large volumes of data. This paper describes a robust methodology for processing time series of satellite data over large spatial areas. The methodology includes a retrospective analysis used for the generation of training and test data for historical periods lacking reference information. This methodology was developed in the context of research on global change in the Iberian Peninsula. In this study we selected two scenes covering geographic regions that are representative of the Iberian Peninsula. For each scene, we present the results of two classifications (1985–1989 and 2000–2004 quinquennia), each with a legend of 13 categories. An overall accuracy of over 92% was obtained for all 4 maps.     

Multiple band digital orthophoto quadrangle data: A source for generating land use maps

Abstract

The purpose of this study was to investigate the use of color infrared‐digital orthophoto quadrangle (CIR‐DOQ) data to generate land use/land cover (LULC) maps and to incorporate them as data layers in geographic information systems (GIS) involving various resource management scenarios. The Danville 7.5‐minute quadrangle located in the southern part of Limestone and Morgan counties, Alabama, was used as the study site. Data for the special CIR‐DOQ were generated by scanning four 9x9 inch CIR aerial photographs at a uniform pixel sample grid of 25 microns resulting in 2 meters ground sample resolution. One‐half of the quadrangle was used to identify training sites for performing a supervised classification of the data and the other half to verify the accuracy of the classification. The CIR‐DOQ data were found to be adequate for using a supervised classification algorithm to differentiate major LULC classes, resulting in a classification accuracy of 93 percent. The superior spatial quality of the data over commençai satellite data affords resource managers an opportunity to more effectively study land cover and surface hydrological properties of an area, soil moisture and surface soil textures, as well as differentiate among vegetation species, using remote sensing techniques. However, caution must be exercised when using multispectral classification techniques to classify mosaicked CIRDOQ data because of the image enhancements used to generate the final product. In its present form, there are some limitations to the use of the data for performing spectral classifications. Hozvever, the high spatial resolution of the data enables even the novice resource planner to effectively use the data in visual interpretations of major LULC classes.     

土地利用基础图件更新软件系统的设计与开发

土地利用基础图件是新一轮国土资源大调查中系列土地调查的基础。随着我国经济建设飞速发展,土地利用状况发生了巨大变化,如何快速、准确地更新土地利用基础图件已成为亟待解决的重要问题。本文阐述了土地利用基础图件更新软件系统的需求、特点、系统功能和实现方法。该软件系统将整个图件更新作业流程一体化,实现了GPS、RS、GIS技术集成支持下的土地利用基础图件的快速更新。     

Improving settlement selection for small-scale maps using data enrichment and machine learning

Acquiring and formalizing cartographic knowledge still is a challenge, especially when the generalization process concerns small-scale maps. We concentrate on the settlement selection process for small-scale maps, with the aim of rendering it more holistic, and making methodological contributions in four areas. First, we show how written specifications and rules can be validated against the actual published map products, thus pointing to gaps and potential improvements. Second, we use data enrichment based on supplementing information extracted from point-of-interest data in order to assign functional importance to particular settlements. Third, we use machine learning (ML) algorithms to infer additional rules from existing maps, thus making explicit the deep knowledge of cartographers and allowing to extend the cartographic rule set. And fourth, we show how the results of ML can be transformed into human-readable form for potential use in the guidelines of national mapping agencies. We use the case of settlement selection in the small-scale maps published by the Polish national mapping agency (GUGiK). However, we believe that the methods and findings of this paper can be adapted to other environments with minor modifications.     

互联网地图视觉质量的影响因素和优化对策

本文从地图制图专业视角出发,归纳互联网地图制图体系的要素及其关系,分析目前地图视觉质量仍待优化的必要性,并揭示现状问题的成因。进而结合互联网地图的特点、媒介环境和技术条件、受众认知与交互需求等,提出影响互联网地图视觉质量的用户考量、研究倾向、参与协同和介质技术等四大因素。由此,强调美学属性是地图必要的有机组分,网络地图服务的功能体验、交互体验、视觉体验相辅相成。最后,基于以用户为中心和跨学科协同的理念,回答了制图实践的方向性问题,从宏观指导、具体原则和实施细节三个层面,探讨了互联网地图视觉质量控制和优化设计的对策建议。