Is remote sensing useful for finding and monitoring urban farms?

As the world becomes increasingly urbanized, the need for fresh fruits and vegetables in urban areas grows while the difficulty of bringing these perishable products to these areas also increases. Small-scale agriculture located in urban areas is a highly effective and profitable way to provide these products to communities that are far from extensive commercial agricultural areas. Here we describe how remote sensing can be used with data mining approaches to monitor urban and peri-urban farms within cities in both developed and developing countries. Using very high resolution satellite imagery together with moderate and coarse resolution imagery and information from social media and the web, we analyze the usefulness of different methods to identify farms within urban boundaries in four countries. The analysis shows how a mixed-method approach is necessary in order to identify where urban farming is occurring and to monitor its change through time. Although remote sensing-based vegetation and water indices were useful, without ancillary data they are not effective at remotely mapping the locations of urban farms. However, remote sensing is a good way to monitor vegetation condition in locations where actively managed urban farms are known to exist.     

Satellite imagery activism: Sharpening the focus on tropical deforestation

Since the first land remote sensing satellite was launched in the early 1970s, government agencies, private companies and research institutions have used satellite imagery data for a growing range of civil and commercial applications focused on natural resource management and exploitation, and environmental monitoring. The global diffusion of remote sensing expertize, along with growing public access to satellite images, has created conditions for improving levels of global transparency. One aspect of this global transparency is the advent of new users of imagery data – or 'imagery activists'– including, among others, issue-oriented nongovernmental organizations (NGOs), media groups, multinational organizations and academic researchers who now are able to access satellite imagery in order to draw domestic and international attention to particular public policy concerns. This paper broadly surveys the contemporary phenomenon of satellite imagery activism and outlines the main challenges facing imagery activists, particularly in relation to deforestation and other forest monitoring issues.     

“Ghost cities” identification using multi-source remote sensing datasets: A case study in Yangtze River Delta

Drastic urbanization has taken place in China during the last two decades. Recently, a considerable number of “ghost cities” have emerged due to the extensive and unreasonable urban expansion which far exceeds the practical demand. In order to investigate “ghost cities”, we proposed a feasible framework by utilizing multi-source remote sensing datasets, including nighttime light imagery, land cover type products and population grid. After eliminating blooming effect of nighttime imagery by a proposed modified optimal threshold method (MOTM) and extracting built-up area from land cover type products, we developed a “ghost city” index (GCI) to quantify and evaluate the intensity of “ghost city” phenomenon in Yangtze River Delta at county/district level. The GCI was established according to the intrinsic features of “ghost cities”, comprising three criteria: consistency of lit area and built-up area, illumination intensity and population density. Then, we explored the spatial pattern of “ghost cities” of different GCI categories and the ternary contour was applied to demonstrate the key factor among three criteria. Our finding implies that “ghost cities” are prominently spatial clustered. Meanwhile, counties and new development zones have higher risk of suffering from the phenomenon, while capital cities and municipal cities have an alleviative effect for ambient regions. Besides, regions with higher intensity of the phenomenon tend to have less balanced composition among three criteria. Our results show good consistency with previous reports and studies, providing a more objective and spatial explicit insight into the “ghost city” phenomenon. Our findings do not only prove the capability of monitoring “ghost cities” using remote sensing data, but would also be beneficial to urban planning and regional sustainable development.     

Monitoring land changes in an urban area using satellite imagery,GIS and landscape metrics

Monitoring land changes is an important activity in landscape planning and resource management. In this study, we analyze urban land changes in Atlanta metropolitan area through the combined use of satellite imagery, geographic information systems (GIS), and landscape metrics. The study site is a fast-growing large metropolis in the United States, which contains a mosaic of complex landscape types. Our method consisted of two major components: remote sensing-based land classification and GIS-based land change analysis. Specifically, we adopted a stratified image classification strategy combined with a GIS-based spatial reclassification procedure to map land classes from Landsat Thematic Mapper (TM) scenes acquired in two different years. Then, we analyzed the spatial variation and expansion of urban land changes across the entire metropolitan area through post classification change detection and a variety of GIS-based operations. We further examined the size, pattern, and nature of land changes using landscape metrics to examine the size, pattern, and nature of land changes. This study has demonstrated the usefulness of integrating remote sensing with GIS and landscape metrics in land change analysis that allows the characterization of spatial patterns and helps reveal the underlying processes of urban land changes. Our results indicate a transition of urbanization patterns in the study site with a limited outward expansion despite the dominant suburbanization process.     

中国大运河沿线城市扩张时空差异研究

自20世纪80年代以来,中国大运河沿线城市建成区规模、空间扩张模式以及空间分布特征都发生了显著变化。虽然当前不缺乏大运河重要河段以及沿线典型城市的研究,但对于大运河沿线城市整体扩张的研究较为少见。论文结合统计数据与遥感数据分析了1984—2016年中国大运河沿线城市建成区扩张速度特征、空间特征以及区域差异。结果显示：① 中国大运河沿线城市建成区扩张速度特征可被归纳为4类,不同类别之间差异显著;② 基于遥感影像提取的运河沿线城市建成区面积通常为相同城市对应年份的统计年鉴中建成区面积的1~2倍;③ 运河沿线城市建成区空间分布整体趋于离散、破碎,江浙地区运河沿线城市的建成区空间分布最离散、破碎,且离散度增长最剧烈。     

Frontiers of urbanization: Identifying and explaining urbanization hot spots in the south of Mexico City using human and remote sensing

This article applies a multi-method approach to develop a better measurement of urbanization dynamics using remote and human sensing based on a GIS platform. The results demonstrate the benefits of bringing human and remote sensing sources together in a framework of hot spot analysis for a megacity such as Mexico City. Furthermore, our analysis suggests that human and remote sensing work well together in detecting the expansion of illegal urban settlements. Looking at the driving factors of illegal settlements, the existence of strong association between the expansion of illegal urban settlements and socioeconomic factors such as unemployment, provides some answers and reveals new questions. Illegal urban growth often leads to the loss of ecological areas in the urban frontiers, especially in areas where the urbanization potential is high. As a consequence, there are conflicts with legal settlers who dislike the illegal expansion. This approach can be extended to and replicated in new urbanizing areas, in particular in Africa and Asia.     

The characteristics of oasis urban expansion and drive mechanism analysis: a case study on Ganzhou District in Hexi Corridor, China

Ganzhou District is an oasis city in the Zhangye Municipality of Gansu Province,China.Based on multi-temporal TM and ETM satellite remote sensing data in 1985,1996,2000,and 2012,and by using corrected figures of land use status over the same periods,the spatial area of Ganzhou District since 1985 was extracted with statistical methods,and urban spatial expansion was measured by quantitative research methods.The characteristics of spatial expansion of Ganzhou District were analyzed by urban expansion rate,expansion intensity index,compactness,fractal dimension,and the city center shift method.The results showed that the built-up area of Ganzhou District increased by 3.46 times during 1985–2012.The expansion in 1985–1996 was slow,during 1996–2000 it was rapid,and during 2000–2012 it was at a high speed.This city mainly expanded to the northeast and northwest.Government decision making had a decisive influence on urban expansion.Initially the expansion was uniform,but later the local transportation,economy,resources,population,and national policies factors had an obvious influence on urban expansion.     

过去40年中国城市扩展及其时空差异分析（英文）

The urban expansion process in China from the 1970 s to 2013 was retrieved based on remote sensing and GIS technology. With the latest zoning method used as reference, annual expansion area per city, urban expansion type, and fractal dimension index were employed to analyze the Chinese urban expansion characteristics and its spatial difference from the aspects of urban expansion process, influence of urban expansion on land use, and urban spatial morphological evolutions. Results indicate that 1) under the powerful guidance of policies, urban expansion in China went through six different stages, and cities in the eastern region entered the rapid expansion period the earliest, followed by cities in the central, northeastern and western regions; 2) cultivated lands and rural settlements and industrial traffic lands were the important land sources for urban expansion in China; the influence of urban expansion on land use in the eastern region was the strongest, followed by the central, northeastern and western regions; 3) urban spatial morphology tended to be complex and was directly related to the adopted spatial expansion mode. Infilling expansion became the main urban expansion mode in the western region first, then in the central and northeastern regions, and finally in the eastern region. This study establishes the foundation for an in-depth recognition of urban expansion in China and optimization of future urban planning.     

无人机遥感在红树林资源调查中的应用

低空无人机（UAV,Unmanned Aerial Vehicles）遥感系统具有数据采集灵活、低成本且可快速获取超高分辨率影像的特色,是传统航空遥感和卫星遥感的重要补充。以广东省和广西壮族自治区交界处的英罗港港湾两侧为研究区域,将无人机遥感系统用于红树林资源的遥感调查,通过无人机航拍获取高分辨率影像,并且使用拼接的影像和目视解译方法提取红树林空间分布信息,进一步选择典型研究样地,采用面向对象的最近邻分类方法对红树林树种类型进行分类研究,并对比综述了无人机遥感和常规航空航天遥感技术对红树林资源调查监测的优缺点,无人机遥感系统非常适用于红树林资源调查。通过2 h 30 min的3架次无人机航飞工作,获取了研究区域25.29 km²的无人机影像,基于无人机影像和面向对象遥感分类方法提取的红树林空间分布信息精度超过了90%。未来无人机遥感系统将可成为调查和监测红树林资源的重要技术手段,可为相关管理部门对红树林资源的保护、管理、开发等方面的工作提供基础信息和技术支持。     

Urban expansion in China and its spatial-temporal differences over the past four decades

The urban expansion process in China from the 1970s to 2013 was retrieved based on remote sensing and GIS technology. With the latest zoning method used as reference, annual expansion area per city, urban expansion type, and fractal dimension index were employed to analyze the Chinese urban expansion characteristics and its spatial difference from the aspects of urban expansion process, influence of urban expansion on land use, and urban spatial morphological evolutions. Results indicate that 1) under the powerful guidance of policies, urban expansion in China went through six different stages, and cities in the eastern region entered the rapid expansion period the earliest, followed by cities in the central, northeastern and western regions; 2) cultivated lands and rural settlements and industrial traffic lands were the important land sources for urban expansion in China; the influence of urban expansion on land use in the eastern region was the strongest, followed by the central, northeastern and western regions; 3) urban spatial morphology tended to be complex and was directly related to the adopted spatial expansion mode. Infilling expansion became the main urban expansion mode in the western region first, then in the central and northeastern regions, and finally in the eastern region. This study establishes the foundation for an in-depth recognition of urban expansion in China and optimization of future urban planning.     

Influence of urban expansion on the urban heat island effect in Shanghai

The urban heat island (UHI) effect resulting from rapid urbanization is attracting increasing attention among the global scientific community. This research analyzed the relationship between urban expansion and the UHI effect utilizing an integrated approach, including urban land interpretation and retrieving land surface temperature based on remote sensing, and spatial overlay analysis for revealing the relationship for different time periods between 1984 and 2014 in Shanghai, China. The results show that (1) the spatiotemporal changes in UHI are consistent with the expansion of urban land, and rapid urban expansion leads to an expansion of the UHI, in particular along roadways. (2) The mode of urban expansion is an important factor influencing the UHI effect. Urban sprawl (urban expansion in the edge-expansion way) is a form of typical expansion that leads to the rapid increase in the UHI. When the urban compactness ratio is less than 0.15, a compact design can effectively control the expansion rate of the UHI and mitigate its range of influence and intensity. However, when the urban compactness ratio is greater than 0.15, the urban design has a marked influence on the UHI ratio index: a more compact form produces a stronger UHI effect. So, finding an equilibrium between urban compactness ratio and urban expansion rate is good for effective urban management and planning.     

Land use/cover changes in the war-ravaged Jaffna Peninsula, Sri Lanka, 1984–early 2004

Temporal and spatial information on land use/cover is a prerequisite for effective planning decisions in the context of social and economic development. Satellite remote sensing data have become increasingly important in the study of land use/cover changes. This paper uses multitemporal satellite data to measure and spatially characterize land use/cover changes in the Jaffna Peninsula, northern Sri Lanka over the two decades from 1984 to early 2004 in terms of potential drivers. Over this period, the Jaffna Peninsula has been impacted severely by armed conflict between the government of Sri Lanka and the Liberation Tigers of Tamil Eelam. A postclassification method is used to compare land use/cover classes from satellite images using Geographical Information Systems (GIS) to analyze the spatial pattern of land use/cover changes over the study period. Results indicate that the land use/cover pattern has been very dynamic since early the 1980s, showing a remarkable decrease in agricultural land use and concomitant increase in non-agricultural land uses. The ethnic conflict and its consequences, particularly large-scale population migrations, have been the main driving forces for such land use/cover changes in the Jaffna Peninsula. The results of this study are not only important in aiding efforts to reconstruct this area after decades of physical and socioeconomic devastation, but should also prompt similarly urgent studies in other inaccessible war-torn areas of the world.     

Snow research in Svalbard–an overview

This paper summarizes the most significant snow-related research that has been conducted in Svalbard. Most of the research has been performed during the 1990s and includes investigations of snow distribution, snow-melt, snow pack characteristics, remote sensing of snow and biological studies where snow conditions play an important role. For example, studies have shown regional trends with about 50% higher amounts of snow accumulation at the east coast of Spitsbergen compared to the west coast. Further, the accumulation rates are about twice as high in the south compared to the north. On average, the increase in accumulation with elevation is 97 mm water equivalents per 100 m increase in elevation. Several researchers reported melt rates, which are primarily driven by incoming short-wave radiation, in the range of 10-20 mm/day during spring. Maximum melt rates close to 70 mm/day have been measured. In addition to presenting an overview of research activities, we discuss new, unpublished results in areas where considerable progress is being made. These are i) modelling of snow distribution, ii) modelling of snowmelt runoff and iii) monitoring of snow coverage by satellite imagery. We also identify some weaknesses in current research activities. They are lacks of i) integration between various studies, ii) comparative studies with other Arctic regions, iii) applying local field studies in models that can be used to study larger areas of Svalbard and, finally, iv) using satellite remote sensing data for operational monitoring purposes.     

Forty years of urban expansion in Beijing: What is the relative importance of physical,socioeconomic, and neighborhood factors?

Urban expansion is one of the major causes of many ecological and environmental problems in urban areas and the surrounding regions. Understanding the process of urban expansion and its driving factors is crucial for urban growth planning and management to mitigate the adverse impacts of such growth. Previous studies have primarily been conducted from a static point of view by examining the process of urban expansion for only one or two time periods. Few studies have investigated the temporal dynamics of the effects of the driving factors in urban expansion. Using Beijing as a case study, this research aims to fill this gap. Urban expansion from 1972 to 2010 was detected from multi-temporal remote sensing images for four time periods. The effects of physical, socioeconomic, and neighborhood factors on urban expansion and their temporal dynamics were investigated using binary logistic regression. In addition, the relative importance of the three types of driving factors was examined using variance partitioning. The results showed that Beijing has undergone rapid and magnificent urban expansion in the past forty years. Physical, socioeconomic, and neighborhood factors have simultaneously affected this expansion. Socioeconomic factors were the most important driving force, except during the period of 1972–1984. In addition, the effects of these driving factors on urban expansion varied with time. The magnitude of the unique effects of physical factors and neighborhood factors declined while that of socioeconomic factors increased along with the urbanization process. The findings of this study can help us better understand the process of urban expansion and thus have important implications for urban planning and management in Beijing and similar cities.     

夜间灯光遥感数据应用综述和展望

在遥感应用研究中,夜间灯光遥感作为发展活跃的一个重要分支,近年来受到越来越多来自自然科学领域和社会经济领域的关注。与传统的光学遥感卫星获取地物辐射信息不同,夜间灯光遥感是获取夜间无云条件下地表发射的可见光-近红外电磁波信息。相比于普通的遥感卫星影像,夜间灯光遥感所使用的夜间灯光影像记录的地表灯光强度信息更直接反映人类活动差异,因而被广泛应用于城市化进程研究、不透水面提取、社会经济指标空间化估算、重大事件评估、生态环境评估等领域。目前,虽然基于夜间灯光数据的应用研究成果正在不断积累,但对成果的系统性总结、整理的研究目前存在着覆盖面不全、时效性不强等不足。基于此,论文通过对近几十年来有关夜间灯光数据的研究成果的详细梳理,从数据处理与技术方法、应用研究等方面进行归纳总结。最后,文章从多源数据融合、应用领域拓展和短周期地表灯光监测3个方面指出了未来的研究热点。     

Using geographical information system and satellite imagery within a numerical simulation of regional urban growth

This paper represents an attempt to combine a geographical information system (GIS) and satellite imagery within a numerical model for the simulation of regional urban growth. The area under study is located in the southeast of France, between the cities of La Ciotat and Toulon. It covers 1600 km². The spatial resolution of the GIS as well as of the remote sensing data is better than one hectare (80 × 80 m²). Two Landsat MSS satellite images were analysed by a supervised maximum likelihood classifier to provide two maps of land use and urban domain for 1976 and 1981. A numerical model for the growth of the density of the population is applied to the urban domain. It takes into account some constraints that are due to the environment as well as the changes of population per city and per year. Seven environmental parameters are defined by pixel and originate from the content of the database, namely, land use, topography, road network, forest properties and forest fire characteristics. The global change in population is given by observations for the first years and by scenarios for the predicted years. The numerical simulation gives maps of the urban domain per year and per scenario. The initial state (year 1976) and the simulated states Tor the years 2000 and 2025 are compared and the differences are discussed briefly.     

近六百年来长江三角洲地区城镇空间与城镇体系格局演变分析

基于历史文献、古地图和现代遥感数据,引入历史学古代城镇形态复原方法,复原（提取）明代以来长江三角洲地区113座城镇7个时间断面（1461年、1820年、1930年、1970年、1980年、2000年和2010年）下的城镇边界,采用扩张速率、扩张效率、首位度指数和位序-规模法则,分析了近六百年来区域城镇空间与城镇体系等级规模演变格局。取得以下研究结果：\mathrm{①}研究时段内,区内城镇用地总规模由205.98 km²增加到6442.19 km²,扩大了31.27倍;城镇扩张经历了萌芽阶段（明清时期）、起步阶段（民国至改革开放前夕）、成长阶段（改革开放至2000年）和加速阶段（2000—2010年）,城镇扩张速率不断加快,但扩张效率有待提升;\mathrm{②}在城镇等级规模空间格局上,明清时期南京与苏州为区内的一级城镇,民国后,上海逐渐取代其地位,从五级城镇发展成为区域核心城镇,四级以上城镇主要集中在长江干流沿岸和太湖流域,五级以下城镇大多集中在安徽;城镇体系呈首位型分布,城镇首位度较高,且改革开放后的城镇首位度较明清与民国时期要高,不同等级规模城镇之间差距扩大,大城镇优势较强。近30年,长江沿岸城镇发展加速,苏锡常都市圈、南京都市圈等逐渐形成并快速发展。     

哈长城市群城镇用地扩展进程及其驱动因素研究

以Landsat TM/ETM+/OLI遥感影像为主要数据源,提取哈长城市群1990、2000、2010、2015 年4 个年份的建设用地信息,采用年均扩展指数、景观扩展指数、多距离空间聚类函数、空间分维度等对城镇用地扩展进程进行分析。结果表明,1990~2015年间,哈长城市群城镇用地增加57 321.47 hm²,增长率为21.05%,整体扩展强度呈上升趋势;空间扩展表现出以中心城市为核心的扩展模式,边缘式增长在各个时期均为主导增长方式;空间扩展聚集性总体表现出“先增强、后减弱”趋势,整体空间结构相对稳定。国家宏观政策、非农业GDP增量和第三产业GDP增量是影响哈长城市群城镇用地扩展的重要因素。GDP增量、非农业人口增量、第二产业GDP增量对城镇用地的扩展起阶段性作用;人均GDP增量与城市用地扩展相关性不显著。     

土地利用变化遥感监测精度评价系统——以随机抽样为基础的方法

中国正在采用遥感技术对 5 0万以上市区非农人口城市的建设用地扩展情况进行分期监测 ,监测结果的精度评价是该项工作的一个重要方面。本文提出以分层随机抽样的方法来获取对遥感监测的精度分析 ,内容包括监测精度评价的指标系统、分层随机抽样样本容量的确定和在各层的分配、抽样评价的工作步骤以及抽样调查的统计分析和结果表达 ,并以北京和重庆 2 0 0 1年的遥感监测数据和实地调查数据为基础进行了精度评价的实际演练。     

俄罗斯典型城市扩张时空格局与驱动机制——基于遥感决策融合与多元离散回归模型

本研究以社会经济发展统计数据和多源遥感影像数据为基础,通过决策融合遥感解译方法、多元离散回归模型、质心迁移、扇形分析法等,重点考察了伊尔库茨克(Irkutsk)、新西伯利亚(Novosibirsk)、叶卡捷琳堡(Yekaterinburg)分别在1990年、2000年、2010年、2018年城市不透水面的扩张特征,探讨了不同城市扩张的自然环境变化与社会经济发展耦合作用与驱动机制。首先不同城市的扩张方向、强度、速度、模式上存在显著时空差异,三个城市分别呈现“快速增长-增长-慢速增长”“增长-增长-慢速增长”“慢速增长-增长-慢速增长”发展趋势,其中叶卡捷琳堡扩张强度最高。而城市新增不透水面的扩张类型以蔓延式和跳跃式扩张为主,填充式扩张所占比重较小。其次典型城市扩张主要发展方向不同,伊尔库茨克城市扩张特征由南北发展向转为放射状发展,新西伯利亚由东西向发展向正西方向发展,叶卡捷琳堡城市扩张特征由放射状发展向西南方向发展,其发展方向与其自然、区位以及社会因素有关,其中自然因素和区位因素是俄罗斯三类典型城市扩张的主导因素。最后文章阐述不同类型的俄罗斯城市其发展方向与城市发展潜力,为其同类型城市发展提供科学管理依据。伊尔库茨克借助丰富旅游资源重视城市内旅游产业发展,新西伯利亚由于历史问题,对城市内外部交通网络布局提出更高标准规划,叶卡捷琳堡作为俄罗斯国内较发达城市,可加强和周边城市联系形成具有联动作用的城市群。对中国东北地区同类型城市发展规划有着一定的启示意义,包括加强发展紧凑城市、注重交通设施建设、加强周边城市联动、发展旅游等。